January 2011
Contents
1. n j 1 5 WAL m mi A service to members 70 annually to subscribers By Dave Hobbs MACS Technical Correspondent THE MOBILE AIR CONDITIONING SOCIETY WORLDWIDE SERVICE MEPORTS Mobile Air Conditioning Society Worldwide January 2011 MASTERING HYBRID HVAC TOYOTA PRIUS PART 2 If you ve made a New Year s Resolution to increase prof its at your shop by finding new repair opportunities look no further than hybrids It s predicted that by the end of this decade over 25 percent of all new vehicles produced will contain some type of hybrid electric technology In the December 2010 MACS Service Reports we took a dive into the HVAC system on the Toyota Prius line along with a quick overview on how hybrid vehicles work in general We also covered safety tips electronic controls and the Gen II Prius electric compressor This month we re going to dive in deeper 2004 2009 Generation Il Prius Peeking Under the Hood Let s take a closer look under the hood starting with the condenser Gen II Prius condensers are multi flow units with a modulator tank on the side that includes a typical Toyota style replaceable drier desiccant bag The refrig erant passes through the modulator and desiccant before taking one last pass through the bottom portion of the condenser which Toyota calls a sub cooler Even though the Prius sports an old fashioned sight glass due to the condenser sub c2. to change high voltage DC to high voltage AC The com pressor is still a variable speed model and has extra con nections with several new control and monitoring circuits related to its inverter multi speed feature Under a removable cover on top of the vehicle s main inverter is a serviceable fuse that you must keep in mind when diagnosing A C complaints Figure 14 Also unique to this new compressor and its control logic is a mode that can be customized with the factory scan tool Techstream Lite will also work to reduce compressor noise and vibra tion that has been a source of some customer complaints MACS Service Reports At The customizable feature is described in Toyota Tech Tip T TT 0040 10 and is simply a method of turning down the maximum compressor speed Toyota recommends discussing the potential for a slight reduction in cooling performance with the customer prior to performing the procedure For the Gen III Prius the term fuzzy logic from the Gen II Prius has been upgraded to Neural Network Control Quoting the definition for the term from Toyota s service manual This control is capable of ef fecting complex control by artificially simulating the information processing method of the nervous system of living organisms in order to establish a complex in put or output relationship that is similar to a human brain Now that s just too strange for me to make up and should give you a c
3. tion to make it work as a scanner Short term subscriptions for 48 hours are available for 55 but when the subscrip tion expires you are now looking at vaporware the scan tool software won t work until you purchase another sub scription FYI if you are a well healed shop that purchased a Tech stream a few years ago at a software level 2 0 or lower you won t be able to scan a 2010 vehicle But the software won t vaporize at the end of your subscription allowing an indefinite time period for scanning Toyota Lexus and Scion vehicles If you choose to renew your subscription to a later version however you ll be in same boat as more MACS Service Reports recent purchasers of these tools who have a timed sub scription that will render the tool useless at the end of the subscription Here s another FYI to shops who may have purchased a Drew Technologies CarDAQ Plus universal J2534 pro grammer it s a little known fact that this tool was also validated by Toyota and will work as a factory scan tool VIM interface the same as the Drew Mongoose Toyota Techstream Lite Another nice feature of either of these in terfaces coupled with a subscription is Toyota s nice job at doing all makes and models Global OBD II and Mode 6 monitor testing for other vehicles The Mode 6 section is easy to read and very graphic in nature Emission monitor tests are red or green good or bad Recent software upgrades have seen t
4. inverter converter not hundreds but thousands of dol lars wouldn t it be nice to have a couple gallons of the right stuff on your parts shelf to feed the engine cooling system AND the hybrid power electronics cooling system One more thing while we re on the subject of hybrid cooling systems it s important to note that the hoses coolant and pumps for the gas engine cooling system are very similar looking to the cooling system components for the hybrid power electronics Be careful not to confuse the two The bottom portion of the Gen II Prius radiator con tains a separate and isolated section to cool the hybrid power electronics The petcock for draining engine cool ant also yellow is located just above this section of the engine s radiator Hybrid HVAC Diagnostics A general note on diagnostics with any hybrid neither the high voltage DC nor the high voltage AC systems use a chassis ground or common neutral circuit as we find in typical automotive 12 volt systems or 115 230 volt resi dential electrical system All HV circuits are isolated from chassis ground although you may measure around of the total high voltage in the vehicle 201 volts divided by WI M January 2011 two with a meter between chassis ground and an orange cable This voltage is limited to extremely low current and is there strictly for diagnostic purposes much like the low current that s always present to ensure an airbag i
5. on cold starts The system works by recovering hot engine coolant storing it in an insulated vacuum tank located in the LF inner fender area and then pumping it into the en A iss Figure 2 In addition to a mechanical water pump on the front of the gas engine there are two electric pumps for coolant one for supplement ing coolant flow for idle stop heater performance a and the other for handling coolant in and out of the heat storage tank b Make sure you disconnect the grey connector from this pump prior to servicing the cool ing system to prevent hot coolant from being pumped out A three way valve c handles management of coolant for either storage in the tank d or preheat of the engine the accuracy of the content of MACS Service Reports MACS however will not be responsible for the accuracy of the informa tion published nor will MACS Worldwide be liable in any way for injury labor parts or other expenses resulting from the use of information appearing in MACS Service Reports January 2011 MACS Service Reports gine prior to the next cold start You might not be able to hear the electric pump turn on while driving but you will notice it turn on and run for a few seconds upon vehicle shut down This is completely normal the storage tank is being filled with hot coolant one last time prior to the next cold start A few things you need to know about these systems First the storage tan
6. 11 Editors Production Designer Manager of Service Training Elvis Hoffpauir Paul DeGuiseppi Laina Casey Paul DeGuiseppi Mobile Air Conditioning Society Worldwide PO Box 88 Lansdale PA 19446 Phone 215 631 7020 Fax 215 631 7017 Email membership macsw org Website www macsw org MACS Service Reports
7. Toyota Techstream Lite Note that the set temperature number drives the compressor speed OTI mue meman Figure 10 Connecting a current probe to this Cat III 1000 volt mul timeter and clamping the probe over one of the heavy high voltage AC lines going to the compressor will tell you the current draw of the compressor The current probe outputs amps to mV COM ma pA January 2011 an inner conductor surrounded by insula tion then a braided ground shield like an antenna coax on top of that and then more orange insulation on top of that A T pin jammed into the center conductor will connect the braided ground shield to that center conductor A direct short of high voltage to ground will be the result Sure hope those electronic safeguards work and your gloves don t have a pinhole in them 2010 2011 Generation Ill Prius Starting with the 2010 model year Toyota fans saw the launch of yet another Prius generation Unless you work at a Toyota dealership you ll not likely see one in your shop for a while but as a heads up we ll cover the highlights of what s new There are a lot of wildly high tech and innova tive new features to say the least Look at the front of the gas engine and right off the bat you see something missing There is no serpentine belt on this vehicle There s no alternator hybrids all use a DC DC converter for that job no power steering pump a 12 volt electric po
8. capability While aftermarket scan tools are making giant leaps in vehicle and system coverage their manufacturers can t possibly invest the time and resources into a single OEM brand like the factory can Most of those reading this aren t in a position to pur chase a factory scan tool for every brand of vehicle they work on That would be extremely cost prohibitive al though many shops are purchasing factory scan tools for the models they most commonly encounter However re garding a factory scan tool there is good news for those of you who work on Toyota Lexus and Scion vehicles For Toyota Prius model years 2001 2008 a factory scan tool meant the Vetronix Mastertech with the yellow Toyota factory program card Beginning in 2009 Toyota Lexus and Scion models began using the Toyota Techstream as the official factory scan tool The combination of a Pana sonic Toughbook laptop PC a Snap On docking station and factory software made this factory scan tool run into January 2011 connected between the car and your laptop you now have a factory level scan tool The subscription easily pays for itself with just the OEM level service information such as wiring schematics TSBs and workshop manual info not to mention full access to calibration downloads for reflashing This package from Toyota is currently 1345 Purchasing the Mongoose from Drew or one of its dis tributors costs around 500 but you ll still need a subscrip
9. his feature take a hiatus but Toyota s Diagnostic Code Code Description Current Pending History Summary airflow recirc and blower control outputs One thing you ll notice when you connect a scan tool is that it can read body HVAC codes Gen II Prius models have a tendency to set DTC B1421 for a solar sensor prob lem Figure 7 I ve looked at the factory information for TSBs and can t find any but almost every Gen II Prius I ve worked on has had this code You clear it and if you are parked inside it comes back So I presume it has some thing to do with artificial lighting as opposed to natural sunlight I ve never experienced a real solar sensor prob lem with any of the Gen II models I ve driven but there are some documented cases of the sensor falling down into the dash as the root cause There are no warning lights customer support folks have indicat ed it could be coming back foe Solar Sensor Circuit Passenger Side x Figure 7 Not every false DTC is the subject of a TSB This solar sensor DTC probably set as a result of simply parking in the service bay where the lighting is relatively poor Deeper HVAC Diagnostics All Gen II and Gen III Prius have ATC Automatic Temp Control systems which utilize the familiar inputs of an outside air temp sensor an aspirated in car air temp sen sor and solar sensors along with the usual temperature or symptoms associated with this DTC so as the say
10. ing goes if it s not broke don t fix it Working on a Gen I Prius HVAC system is similar to working on any other Toyota HVAC system but the Gen _ Parameter Vawe Unit Parameter Value Unit Room Temperature Sensor 77 45 F 85 82 F 83 70 F Foot DEF Auto Mode ON 52 25 F Foot DEF Auto BlowUp ON Foot Air Leak Ambient Temperature Shift vaporator Temp Sensor olar Sensor D Side ngine Coolant Temp et Temperature D Side 77 35 F f2 F 10 0 63 0 9 5 10 0 Air Outlet Damper Position Air Mix Damper Target D 10 0 and Free Telephone lower Motor Speed Level umidity Sensor 8 33 rpm rpm d umber of Trouble Codes hift Set Temperature Air Inlet Mode 3000 7745 85 82 83 70 52 25 0 177 35 72 710 0 63 0 795 710 0 6 3000 _ Normal _ _ Auto Room Temperature Sensor _ Foot Air Leak Ambient Temperature Shift __ o o LS a E E a o o o o o o o Air Inlet Mode _ o O Figure 8 Gen II Prius HVAC PIDS from the Toyota Techstream Lite Note compressor speed and target speed They should be very close in rpm January 2011 5 MACS Service Reports II with its use of a variable speed electric compressor is a different story Compressor speed is an output of the hy brid ECU and can be viewed as a scan tool PID Figures 8 9 Specs from DENSO indicate that the compressor can run up to 7500 rpm and use around 3 4 kW of electrical power which c
11. k s location makes it vulnerable to Figure 3 The view you are most likely to see from under the vehicle The yellow petcock allows for tank draining A temp sensor helps the ECM determine outlet temperature when the pump ts turned on and the control valve directs the coolant towards the engine r AP S60 AA i ita CAUTION ATTENTION Figure 4 With the plastic trim cover removed from the upper radiator support you will find a 6 mm hex fitting in an air bleed valve in the top left of the radiator Open this while running the electric pump with a scan tool to help purge the system of air when a coolant refill is being performed January 2011 damage even after a minor collision So keep that in mind when working on engine coolant leak complaints after a fender bender Second there is a potential for burns from hot coolant when the system is opened during service Even several hours after you expect the coolant to be nice and cool it is NOT This tank will keep the coolant hot well past an overnight cold soak period Plus the electric pump that moves coolant in and out of the tank may run with the IP power switch off so unplug the two wire electrical con nector for this pump which is located next to the storage tank whenever ser vicing the cooling system That said the ECM may attempt to activate the pump while you have it disconnected and that will cause either a DTC P1151 or P2601 to set Be sure you c
12. lear those codes later While we re on the subject of this pump there is a Toyota bulletin T SB 0087 08 addressing an improved pump should your customer s become noisy Third this tank contains coolant that needs to be included in your flushing procedures The tank is the lowest point in the gas engine s cooling system so traditional draining of the radiator and block won t do You need to open the yellow petcock Figure 3 in the bottom of the storage tank in order to do a complete flush and fill unless you use a factory scan tool that can send a bi directional com mand to the ECM to open up the system while you use your cool ant flushing equipment With all this hardware pumps control valves and hot coolant reservoirs there is plenty of op portunity for an air lock when servicing a hybrid s gas engine s cooling system so an Airlift tool is paramount in importance along with a scan tool to run the electric coolant pump Don t for get to open the air bleed Figure 4 in the top of the radiator left side as recommended by the OEM service manual The mechanical water pumps on these cars are somewhat prone to failure once they get past the MACS Service Reports 100K mile point I happened to be visiting a shop in Jack son Mississippi on a day when a tech was replacing one The subject of coolant brand and type came up Here we go again with a potential can of worms If you can t already te
13. ll I favor factory recommenda tions especially on things that are not old hat to me Hy brids haven t become old hat to me yet so we had the parts chaser run to the local Toyota dealer to get the coolant they use Guess what we were given Universal Brand X cool ant I really wanted what the manual said to use To quote the Toyota TIS Technical Information System Use only TOYOTA Super Long Life Coolant or similar high quality ethylene glycol based non silicate non amine non nitrite and non borate coolant with long life hybrid organic acid technology Coolant with long life hybrid organic acid technology consists of a combination of low phosphates and organic acids The key words would be long life non silicate and HOAT hybrid organic acid technology Using the wrong coolant can at the very least reduce that long cool ant service life we expect these days not to mention pres ent the potential for long term degradation of cooling sys tem components Heater cores for example have tubes so thin that high mineral tap water or high silicate antifreeze can cause leaks down the road Since the same type of Toyota coolant is used to cool the hybrid power electronics inverters and converters it would be good to use exactly what Toyota says to use After all the jury has not yet re turned on the effects of alternative coolants on these major components hoses and seals Considering the price for an
14. lue that the algorithms operating instructions for the modules are extremely advanced on this new model of Prius The factory service manual goes on in much greater detail to give you the picture that these are not just cars for technicians they are IQ tests Not to worry however As these new models begin to accumulate miles and their HVAC systems begin to need service MACS will continue its tradi tion of unraveling the mysteries of automotive HVAC diagnostics for service professionals W mi DO NOT remove the al On i BEE 1 kd GEN of Le NE en renueeatic 4s Figure 14 Hidden by a removable cover and connecting DC power coming from the battery pack a to the compressor inverter is a fuse b held in with screws NEVER remove this cover without exercising proper high voltage power down and safety procedures Connections for MG1 c and MG2 d are also accessed under this cover MACS Service Reports is published monthly by the Mobile Air Conditioning Soci ety Worldwide It is distributed to members of MACS Worldwide and is intended for the educational use of members of the automotive air conditioning service and repair industry Suggestions for articles will be considered for publication however MACS Worldwide reserves the right to choose and edit all submissions Nonmembers wishing to receive MACS Service Reports should contact the na tional office Non member price for 12 issues is 70 January 20
15. measure into the giga ohms realm Another problem that can occur with a hybrid vehicle is electrical imbalance in the windings of a three phase electric motor such as a motor generator in a transmission or the three phase AC HVAC compressor An instrument called a milliohm meter is available to test for a precise balance in resistance in a set of motor wind ings Figure 6 I haven t performed exhaustive testing of the most pop the 7K mark However in the last few months another Techstream was released by Toyota Called Techstream Lite this factory scan tool for the aftermarket almost mir rors the capability of the more expensive full Techstream for OBD II compliant vehicles You basically supply your own laptop and purchase the interface VIM Vehicle Inter face Module from Toyota along with a subscription to the Toyota TIS website at the professional level The subscrip tion lasts for one year and with it you receive the Drew Technologies OE specific J2534 programming interface that Drew calls their Mongoose line With factory scan tool software downloaded onto your PC and the J2534 flasher Figure 6 A milliohm meter can help determine if some of the windings in a three phase electric motor are imbalanced by measuring extremely low resis tance ular aftermarket scan tools but as a general statement it is unlikely you ll see every PID in every module on a hybrid using an aftermarket scan tool nor every bi directional
16. omes out to around 17 amps if you use Watt s Law Wax COLD MAX COLD FullScreen ff SraphType fm Lull Soreen raph Type E Wearing Class 0 gloves safety glasses and using a CAT III 1000 volt meter I ve carefully peeled back the orange flexible conduit from the 3 three phase cables leading to the electric compressor and connected an inductive high voltage AC amp clamp around one of the cables Mea sured current draw was 7 8 amps on a 70 degree F day Figure 10 By the way please don t even think about back probing or piercing ANY orange HV ca bles ona hybrid The result will very likely be a no start condition Since there is no 12 volt electric starter to crank the gas engine on a hybrid Toyota or Lexus one of the HV motor generators cranks the engine at around 1000 rpm whenever it needs to start In order for this to happen the hybrid s electronics must be happy with the state of various relays and controls in addition to the condition of the HV wiring insulation Just like a GFI in your house automatically pops a breaker to shut down a shorted circuit to prevent shock or electrical fires the safeguards on hybrid elec tric vehicles do the much the same A tiny pinhole in a high voltage wire or around a connector could cause an arc and potential shock hazard and induce a complete system shut down Also orange cables often have Figure 9 Gen II Prius HVAC PIDS graphed from the
17. ool cycle design bubbles in the sight glass will disappear prior to the system being fully charged This means a add refrigerant and watch the sight glass Improper service methods may Cause injury Air conditioning system should be service by qualified personnel See Repair Manual Refrigerant oil 52kg 1 14lbs ND OIL SAE ay Min 0 A21 Oaaibs OR EQUIVALENT J 639 MFD BY DENSO MANUFACTURING MICHIGAN INC Figure 1 There s no mistaking the correct oil type and charge amount for the Gen II Prius Don t use the sight glass while charging With changing technology it is more important than ever to follow OEM guidelines MACS Service Reports is the official technical publication of the Mobile Air Conditioning Society Worldwide Inc P O Box 88 Lansdale PA 19446 The material published in MACS Service Reports expresses the views of the contributors and not neces sarily that of MACS Every attempt has been made to ensure till its clear charge method will leave the system under charged The system charge is only 16 ounces nominally Figure 1 which makes it a good candidate for charging with the newer and more accurate breed of J2788 R R R machines Radically unique on the Gen II Prius is its coolant heat storage system Figure 2 The system is an emissions re duction device that helps these cars achieve AT SULEV Advanced Technology Super Ultra Low Emission Ve hicle EPA status by lowering the hydrocarbon output
18. s prop erly connected in a SIR circuit As mentioned in Part 1 of this report the proper high voltage power down procedure along with leak checked Class 0 1000 volt rubber gloves with leather covers to protect them and a Category II 1000 volt multimeter Figure 5 are mandatory when working on hybrids Make sure that not only is your meter rated for hybrids but that your leads and probes are as well If you encounter a DTC that indicates a leaky high voltage cable or component such as the electric A C compressor you may not be able to visually determine where the problem is The leak may be a pinhole size intrusion in a high voltage cable Unlike leaky spark plug wires that can be tested with a fine mist of water while power braking the engine you can t do such a stress test with a hybrid s high voltage cables With the system properly powered down you can however con nect a special meter sometimes called a mega ohm meter between an insulated terminal and chassis ground Figure 5 Not only is the Fluke 1587 multimeter a Category III 1000 volt meter suitable for hybrids it also has a insulation test feature for detecting high resistance leaks in the insulation of cables or components MACS Service Reports Most ohm meters put out between 5 and 2 volts when in their resistance test mode Insulation testers can put out between 250 and 1000 volts into a circuit to test for high resistance shorts to ground The meter can
19. ther option a remote A C control that allows the driver to press a button on the key fob to activate the HV system for three minutes This allows the hybrid elec tric compressor to turn on and cool the car down The HVAC controls for this model are in a more con ventional looking head unit which communicates to an A C amplifier Figure 12 Early production models had issues with the LCD panel being hard to see Toyota bulle tin T SB 0387 09 addresses the problem with a new control head available The Gen III Prius battery pack retains the 201 volts of its predecessor The inverter converter assembly has been moved from of the top of the transaxle and downsized The A C compressor is still HV electric with orange cables but not three orange cables as the Gen II models had The Gen III has two larger gauge DC HV cables one January 2011 Sr 7 Figure 12 2010 Prius owners have complained about the LCD panel in the HVAC head being difficult to read A new control head is available per a Toyota TSB cable for positive and one for negative Figure 13 This new A C compressor contains its own DC AC inverter Figure 13 New for the 2010 Toyota hybrid electric compressor is an or ange connector with two orange wires that carry the HV DC supply volt age from the inverter converter assembly and a connector for the 12 volt electronic controls for monitoring the compressor A DC to AC inverter is built inside the compressor
20. wer steering system is used and there is also no mechanical water pump because the main pump to move coolant under all conditions is now an electrical ly operated 12 volt pump Next up for the Gen III Prius is an optional solar panel MACS Service Reports located in the vehicle s moon roof No it doesn t charge the HV battery pack but performs the task of running the blower to provide ventilation in a hot car parked in the sun There is a manual switch on models equipped with this feature to turn it off In cases of winter climates where sun load is a pleasurable happening you wouldn t want to ventilate the warm air out of the car Speaking of winter a much larger PTC heater is used on this model To help with emissions and heater core opera tion on the Gen III cars the hot coolant storage tank from the Gen II models has been replaced with a system that uses heat from the catalytic converter to heat engine cool ant Figure 11 Figure 11 2010 Gen III Prius models are equipped with an exhaust sys tem coolant heater For reduced cold start emissions as well has faster cabin heater performance heat from the catalytic converter is utilized to assist in warming up the engine coolant Another notable feature is an optional Plasmacluster generator It is basically a variation of those electric air pu rifiers that lower pollutants in the air If those features weren t enough for your fancy there s still yet ano
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