Keeping Electricals Cool Keeping Electricals Cool
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1. he Prius uses an independent cooling system to keep the inverter and motor generator M G at a safe temperature In warm weather problems with the inverter cooling system are fairly common in both the Gen 1 Prius 2001 2003 and Gen 2 Prius 2004 2009 If youre not already familiar with these systems this article will bring you up to speed and save you some time when the first failure rolls through your bay door m ets start with an overview of the basics The inverter cooling system is completely independent of the ICE Internal Combustion Engine cooling system It uses a separate radiator and water pump and it operates at a lower temperature than the ICE cooling system KK SEPING TESK LEC MICA is l4 N by Paul Cortes Coolant mmm The inverter cooling system uses the same type of coolant as the ICE cooling system Gen 1 was factory filled with Toyota Long Life Coolant LLC LLC is full strength and must be mixed with distilled water to obtain the correct ratio 50 50 Gen 2 was factory filled with Toyota Super Long Life Coolant SLLC SLLC is premixed eliminating the hassle of mixing and the potential for error mmm SLLC can be used in Gen 1 but LLC should not be used in Gen 2 The Gen 1 maintenance schedule calls Radiator for Inverter Radiator for Engine Condenser Radiator for Engine Radiator for Inverter 2nd Generation Prius for coolant replacement every 302. alternator like symptoms The car may even stall and require a tow The DC DC converter will probably work OK once the auxiliary battery is charged and the inverter cooling system problem has been corrected m Once you ve found a P3130 INF Code 346 a visual inspection is the first step Is the coolant level low Are any hoses kinked Are the radiator fins blocked If not the next step is to remove the inverter reservoir cap and check to see if the coolant is flowing You should see a fair amount of burbling If there is a If the coolant is still or barely moving there s a problem When the pump is working properly you Should see a fair amount of turbulence 6 IMPORT SERVICE www mastertechmag com The inverter reservoir can become Opaque as it ages A flashlight is helpful when checking the level d Use a seam splitter to slit the protective sheath and then use piercing probes to check voltage placid pool of pink tranquility under the cap check for voltage across the two wire connector at the inverter pump with the power mode in READY or ON No coolant flow Battery voltage across the inverter pump Bad inverter pump Simple huh Flat rate diagnostic guys rejoice ma lf you pull enough inverter reservoir caps off you may notice that some cars with no codes also have no flow The right combination of driving style and ambient temperature may allow a Prius with a bad inverter pump to continue driving t
3. damaged during collisions or repairs You may need a mirror and some patience to fully inspect all of the inverter system hoses CONCLUSION ma Most techs will have no trouble diagnosing and repairing the inverter cooling system provided they have a Techstream and vacuum bleeding tool The common mechanical failures are covered by TSBs and collision related surprises shouldn t present much of a challenge since this system has more diagnostic capabilities and less complexity than a standard ICE cooling system amp This hose was pinched January 2010 IMPORT SERVICE g PMIUS INVEATER COOLING REPLACING AN INVERTER PUMP ON A GEN 1 PRIUS 1 Remove the inverter reservoir 3 Here is the hidden headlight cap then remove the inverter nut The other two fasteners drain plug in the transaxle are on the top of the headlight housing in plain sight ec Remove the bumper cover 4 There is a retaining clip in the This is necessary because the inner lower corner of the housing bumper blocks access to one of Just pull the headlight housing the headlight bolts Most of the towards you to release it bumpers fasteners are obvious except for the two nuts hidden in the wheel well 10 IMPORT SERVICE ww mastertechmag com 5 Once the headlight is out of the Install the inverter drain plug way the pump is easy to access and torque it to 29 ft lb Use a vacuum fill tool to fill and If you are planning to reuse bleed the
4. system the hoses use a hose pick to separate the hoses from the inlet and outlet January 2010 IMPORT SERVICE
5. K miles but the Gen 2 schedule neglects the coolant for 100K miles You may want to consider stocking only SLLC It will cover 100 of the Toyota line It s easier to use since there is no need to premix or stock distilled water And it s arguably a superior coolant The only down side is a slightly higher cost per mixed gallon TEMPERATURE REGULATION m Since the inverter and M G do not need to achieve operating temperature to work efficiently there s no need for a thermostat or other temperature based control of the inverter pump The inverter pump runs any time the power mode is ON or READY Receiver Tank Le Water Pump BE SK Condenser Radiator for Engine Radiator for Inverter 1st Generation Prius What s hot ma The heat in the inverter coolant comes from two sources the inverter and the M G Heat sinks in the inverter and the transaxle transfer heat into the coolant The inverter radiator removes heat from the coolant and the design and location changes from Gen 1 to Gen 2 The inverter radiators are both positioned to avoid radiant heat from the ICE radiator wa With Gen 1 the inverter radiator is located between the ICE radiator assembly and the bumper It might be mistaken for an oil cooler if it were not for the 16mm coolant hoses attached to it January 2010 IMPORT SERVICE 3 we 1 INVEATERA COOLING m On Gen 2 the inverter radiator is the lower s
6. ection of the ICE radiator but the ICE and the inverter sections are compartmented no coolant is shared between the two The division is hard to see while with the radiator is mounted in the car but it s there Fans amp Pump ma The inverter radiator is cooled by the same set of electric fans used for the condenser and radiator Water pumps are a source of confusion for many The Gen 2 Prius has 4 water pumps total ICE water pump heater water pump thermos water pump and the inverter water pump Sorting out what s what can be time consuming just by itself if you re not familiar with the Prius You ll find the inverter pump mounted on the body just behind the driver s side headlight on both the Gen 1 and Gen 2 The MGe heat sink is on the very top of the transaxle NECESSARY TOOLS Scan tool ma The most important piece of equipment for any Prius diagnosis or repair is the Techstream scan tool An older Toyota Intelligent Tester or Vetronix Mastertech with a Genuine Toyota card will also work but is much slower and does not have the same features Other scan tools have promised full coverage but so far none has delivered at least not reliably Using one that lacks capability or provides incorrect information can waste hours of diagnostic time Any shop can purchase a Techstream Here Vacuum Fill Tool A K A Air Lift The transaxle heat sink is near the top of the transaxle and the inlet outlet p
7. ipes are near the center of the transaxle The heat sink chamber can become air locked during service A vacuum fill tool is the Its hard to remove air pockets from this area without a vacuum fill tool te al ae _ ate mE Ag Ak parei a q4 IMPORT SEAVICE www mastertechmag com A shies nn best way to ensure no air is trapped when refilling the system Depending on the design of the vacuum fill tool you may also need a cap adaptor Safety Equipment ma Lineman s gloves CAT IV rated test equipment and other hybrid safety issues have been discussed ad nauseam in many publications and training courses to the point of crowding out more useful material so I won t torture you by repeating more of the same If you are not already familiar with hybrid safety please read the safety information in the service manual before starting work The most important safety precaution is being sure you understand the system you are servicing Asking and answering the questions How does this work and How can it hurt me will provide far more for your safety and diagnostic capability than a set of rubber gloves PUMP DIAGNOSIS The most common failure for both the Gen 1 and Gen 2 is the inverter pump There are TSBs addressing this and improved design pumps for both the Gen 1 and the Gen 2 Diagnosis of a failed inverter pump is usually pretty simple but virtually any Prius diagnosis should star
8. of warranty 8 years 100K miles this could be a pricey repair for your customer If the inverter pump is original it makes sense to do your best to confirm that the problem is not caused by an intermittent pump failure In fact replacing a seemingly good pump with an updated unit might be a gamble your customer is willing to take A few Piercing probes can save a lot of time and can often provide more reliable contact than Bback probing but always remember to repair any Insulation holes and rewrap the harness January 2010 IMPORT SERVICE 7 PMIUS INVEATER COOLING hundred dollars wagered on a new pump may save a few thousand Then again the money may buy nothing more than an assurance that an expensive repair was really needed CRAASH Collision damage to components of the inverter cooling system is common The inverter radiator is IMPORT SEAVICE www mastertechmag com obviously in harm s way but the inverter inverter pump hoses and even the transaxle can be damaged when a Prius is smacked in the front Frequently the damage is subtle and will go un noticed during the body shop repair You may encounter a Prius that has been repaired and on the road for months with low coolant and a P3130 or POA93 ma Inverters can be cracked by impact or sometimes the inverter reservoir outlet will crack where it enters the inverter If the reservoir cracks the inverter can be pressure tested u
9. rouble free This common lack of flow was one of the problems with the Gen 1 inverter bleeding procedure found in the service manual Half of the time the coolant flow was imperceptible or non existent which made following the bleeding instructions an endless loop Lt l AUTOMOTIVE FLUKE 88 W MULTIMETER G F RANGE AutoHOLD 7 e ED mm If the pump is powered coolant should be flowing i A g e sy v r gt A ia m s D ck E k D e repeating steps H through L forever You may also run into inverter pumps that work intermittently Flat rate guys may stop rejoicing when they encounter one of these Gen 2 m The Gen 2 Prius has a different trouble code for the inverter cooling system POA93 INF code 346 but the diagnostic procedure is the same TSB EG001 07 recommends that the inverter pump be replaced if no trouble is found during the standard testing m not sure if this is an acknowledgement of the possibility of an intermittent failure or an indication the old pump design lacks pumping capacity Regardless after checking the basics pump replacement is the best option INVERTER Gen 1 TSB EG023 07 which addresses the improved inverter water pump also contains a Plan B If the inverter pump flow seems adequate and the code set while ambient temperature was above 90 deg F Plan B is to replace the inverter with an updated unit If the inverter is out
10. sing a single hole stopper and 16mm cap before spending money on a new reservoir Tire leak detection fluid soapy water in a spray bottle works great for this Only use a regulated air supply not shop air While not directly related to the inverter cooling system you may encounter the following during cooling system repair When the inverter is hit the rear mount bracket is often bent If you remove the two front mounts and the inverter goes SPROINGNGNG as it jumps up a few inches this is probably the case The ABS VSC actuator is mounted to the rear mount bracket If you ve never done one plan on it taking at least six hours This job cannot be done without the Techstream since you ll need it for ABS bleeding and calibration The redesigned Gen 1 inverter pump can be identified by the silver colored bracket The rear inverter mounting point is circled A new hose clamp won t fix this one Transaxles can be damaged at the coolant fittings Sometimes body shops will figure the leak is coming from the hose install a hose clamp and then assume it s fixed I ve seen post collision repair leaks from these fittings twice now There s only one right fix a new transaxle an option that s bound to be unpopular with your customer or their insurance company Toyota hoses are of superior quality so it s unusual to see a leaking hose even after eight years of service However hoses do get
11. t with a Health Check if for no other reason than to establish a baseline Even if youre pretty sure there will be no codes when you start work you ll always want to check for codes post repair to make sure you haven t caused any to set If you don t perform a baseline check how will you know which codes you caused and which were pre existing Gen 1 m lnverter water pump failure diagnosis typically begins with finding a P3130 INF Code 346 P3130 Always start with a Health Check hs rte rM alfunc tio ae es am o err When a P3130 and P3ie5 set FTE ignore the P3le5 January 2010 IMPORT SERVICE 5 oe INVEATERA COOLING indicates a problem with the inverter cooling system and INF Code 346 specifies that the problem is with the water pump INF Code 347 indicates trouble with the cooling fan I assume the HV ECU logic uses the ICE coolant temperature to determine that the fan is at fault but I don t know this for a fact m Sometimes there will also be a P3125 INF Code 264 DC DC converter malfunction and a bunch of low voltage related codes in the ABS VSC ECU Transmission Control ECU etc Ignore these codes for now When the inverter overheats the DC DC converter part of the inverter will stop working The DC DC converter charges the 12V battery like a generator on a standard car so your customer may report dimming lights the Multi Function Display MFD screen flickering or similar
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