Not possible... but my tranny is slipping...

edthefox5 · Dec 2, 2008

First don't touch the megger output it will shock the sh*t out of you.

What is the exact impedance to ground you are seeing with the megger? Your post seems to be implying a low impedance load since your saying short.I find it hard to believe the Inverter would tolerate that. If you have a low impedance on these windings to case what exactly do they measure with a regular ohm meter please? But I would not be surprised to see some very high impedance there as you are testing the conductivity of the coil coating. Maybe 5 meg ohm or more.
The secondary of the Inverter SMPS is floated in respect to chassis ground but the Primary is not. Any impedance to ground on the secondary pulls big primary current and exciting things happen in the CVT case and the Inverter.
And a bare winding not necessarily dead shorted to the case but just exposed to CVT fluid at 100-200 volts at 50-100 amps would do just that.

edthefox5 · Dec 2, 2008

bwilson4web said: ↑

This poses an interesting thought, using house power through a current limiting light bulb to test stator coils:

lift front wheels

disconnect primary power leads from inverter

using a 200 W. current limiting light bulb, test pairs of the three power leads

expected result: a 60 Hz buzzing from the transaxle of equal sound level; also equal AC current for all combinations

If the windings are OK, I would expect all stators to equally rock the respective rotors at 60 Hz. This should be easily heard or felt at the wheels and the intensity should be identical. If one or more stators has failed, I would expect asymmetry in the sound.

The stators are all tied to a common point so as you apply power, you are enabling 'sets of stators.'

It may make sense to take an early transaxle oil sample. The fill hole is located at the front and if you can snake a tube in, you can draw a sample. You'd be looking for discoloration and burn smells.

Of course the ultimate sample is to drain the oil (take a sample) and then drop the pan. The pan may contain interesting debris material. Short of taking the transaxle out (entails engine removal) this is about as invasive as one can get without big problems.

I agree with Patrick on the order of 'swaps' if you go that way. However, I'm not happy with that approach. I would prefer to diagnose the problem(s) and parts swapping is always ugly. The HV ECU is not that bad and you might want to take a quick peek there first. The inverter is a about a 2-4 hour job, not too bad. But swapping the transaxle starts with removing the engine and transaxle from the car. This one is very ugly.

I wish we could get someone with a Graham scanner to visit and look through the codes. I find it all but impossible that there weren't any unless it is the HV ECU that has gone bad.

Bob Wilson
Click to expand...

Hi Bob,
Have used the lightbulb trick for stereo repairs for years & years but you quickly find out you need one hell of a big light bulb for really powerful amps. IF the load is high it just lights the light bulb up nice and bright and drops no current to the unit under test which is cool because you instantly know you have a shorted output on your stereo but I think given the current draw on these MG's there's not a big enough filament you could find that wouldn't just light the bulb up really bright and provide no current to the motor. It's a very good idea and may work but I'm thinking the motors pull way to much power for the light bulb trick.Big motors.
And he's right about how the phase's work. Any voltage induced on any of the coils will turn the wheels. It kicks the motor around to the next phase. Each phase is 120 degree's apart. But I would be hesitant to hook up house current to it even at low voltage to test it. It might not like the 60 hz.

Merc05h · Dec 2, 2008

edthefox5 said: ↑

First don't touch the megger output it will shock the sh*t out of you.

What is the exact impedance to ground you are seeing with the megger? Your post seems to be implying a low impedance load since your saying short.I find it hard to believe the Inverter would tolerate that. If you have a low impedance on these windings to case what exactly do they measure with a regular ohm meter please? But I would not be surprised to see some very high impedance there as you are testing the conductivity of the coil coating. Maybe 5 meg ohm or more.
The secondary of the Inverter SMPS is floated in respect to chassis ground but the Primary is not. Any impedance to ground on the secondary pulls big primary current and exciting things happen in the CVT case and the Inverter.
And a bare winding not necessarily dead shorted to the case but just exposed to CVT fluid at 100-200 volts at 50-100 amps would do just that.
Click to expand...

Unfortunatly I didn't write it down. I just checked against the manual and went on. I'll get that info though and post it. I work for UP/BN Railroad and do troubleshooting on Diesel/Electric Locomotives (usually mechanical, but can get electrical too. Believe Me! I know my megger will shock the hell out of you (guess how!? I could tell you a funny story about sitting on the leads, but I won't. It's too embarising. I have an old megger that you turn on and off, not just press a button.).
I'm very aware of what DC will do to you. For that matter AC also. I haven't done much on it because I'm very busy and it gets dark around here about 5:30 and I don't get home till 6-7. Will do some more work on it this weekend. Thanks for the info on the short not nessessarly to ground and could be through the ATF. Hadn't thought of that. Also didn't know (but it makes sense) that the high voltage is not grounded to chassis. I would have figgured that out from the wiring diagram, but again, didn't think of it. So far all I have other than what I've already posted is that Toyota called me and left on my answering machine at home that they are willing to go half the price of the transmission repair. Funny thing is the girl said this is contingent on my signing a 'non disclosure agreement'. Not sure how they mean that. Non disclosure of a bad tranny, or that they were nice enough to give it to me at half price? Anyway, I'll keep you guys posted and tickle your brains for help till I get it fixed. Thanks Ed, and all for your help. -- Bob Jones

Merc05h · Dec 2, 2008

bwilson4web said: ↑

This poses an interesting thought, using house power through a current limiting light bulb to test stator coils:

lift front wheels

disconnect primary power leads from inverter

using a 200 W. current limiting light bulb, test pairs of the three power leads

expected result: a 60 Hz buzzing from the transaxle of equal sound level; also equal AC current for all combinations

If the windings are OK, I would expect all stators to equally rock the respective rotors at 60 Hz. This should be easily heard or felt at the wheels and the intensity should be identical. If one or more stators has failed, I would expect asymmetry in the sound.

The stators are all tied to a common point so as you apply power, you are enabling 'sets of stators.'

It may make sense to take an early transaxle oil sample. The fill hole is located at the front and if you can snake a tube in, you can draw a sample. You'd be looking for discoloration and burn smells.

Of course the ultimate sample is to drain the oil (take a sample) and then drop the pan. The pan may contain interesting debris material. Short of taking the transaxle out (entails engine removal) this is about as invasive as one can get without big problems.

I agree with Patrick on the order of 'swaps' if you go that way. However, I'm not happy with that approach. I would prefer to diagnose the problem(s) and parts swapping is always ugly. The HV ECU is not that bad and you might want to take a quick peek there first. The inverter is a about a 2-4 hour job, not too bad. But swapping the transaxle starts with removing the engine and transaxle from the car. This one is very ugly.

I wish we could get someone with a Graham scanner to visit and look through the codes. I find it all but impossible that there weren't any unless it is the HV ECU that has gone bad.

Bob Wilson
Click to expand...

Thanks Bob, I'll try that this weekend. Let you know how it goes. What is a Graham Scanner anyway. Not acquainted with the name/type. Yea, I understand the easiest way to do the engine/transaxel swap is to drop the engine/trans and lift the body off it. Leaving the engine/trans on a cart or something. Ohhhh the Pain....... -- Bob Jones

edthefox5 · Dec 2, 2008

Merc05h said: ↑

Unfortunatly I didn't write it down. I just checked against the manual and went on. I'll get that info though and post it. I work for UP/BN Railroad and do troubleshooting on Diesel/Electric Locomotives (usually mechanical, but can get electrical too. Believe Me! I know my megger will shock the hell out of you (guess how!? I could tell you a funny story about sitting on the leads, but I won't. It's too embarising. I have an old megger that you turn on and off, not just press a button.).
I'm very aware of what DC will do to you. For that matter AC also. I haven't done much on it because I'm very busy and it gets dark around here about 5:30 and I don't get home till 6-7. Will do some more work on it this weekend. Thanks for the info on the short not nessessarly to ground and could be through the ATF. Hadn't thought of that. Also didn't know (but it makes sense) that the high voltage is not grounded to chassis. I would have figgured that out from the wiring diagram, but again, didn't think of it. So far all I have other than what I've already posted is that Toyota called me and left on my answering machine at home that they are willing to go half the price of the transmission repair. Funny thing is the girl said this is contingent on my signing a 'non disclosure agreement'. Not sure how they mean that. Non disclosure of a bad tranny, or that they were nice enough to give it to me at half price? Anyway, I'll keep you guys posted and tickle your brains for help till I get it fixed. Thanks Ed, and all for your help. -- Bob Jones
Click to expand...

I'm sorry Bob I was replying to Sagebrush's earlier post. I should have quoted it. I now see that Sagebrush was quoting an earlier example too. Sorry to both of you. Early morning of a night with no sleep. But Sagebrush's post had some interesting stuff though.You unfortunately have stumbled into an area of great interest for some of us. The Prius CVT failure and how does it fail? How to test it when it fails. Its hard to test jig out the Inverter.
But I keep thinking of you saying it lurches which to me may mean one of the phases is inoperative either open or a compromised stator coil covering. If you go ahead with the trans replacement please ask the service advisor what happens to the old tranny. Does it go back to Japan for an autopsy? Thanks.

Not possible... but my tranny is slipping...

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Not possible... but my tranny is slipping...

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