Gen 3 A/C problems!

I looked them up for you. Not quite sure what to make of it though. Could be a wiring or connector fault. You might try re-seating all associated connectors. Personally, I would be off to the dealer service bays myself.

Code 71
A/C Inverter High Voltage
Power Resource System
Malfunction
1. Electric vehicle fuse
2. No. 2 engine wire (harness or connector
between compressor with motor assembly and
inverter with converter assembly)
3. Compressor with motor assembly
4. Hybrid control system
5. CAN communication system

Code 74
A/C Inverter Malfunction
1. Compressor with motor assembly
2. CAN communication system

Code 98
Communication Malfunction
(A/C Inverter Local)
1. Harness or connector between power
management control ECU, compressor with
motor assembly and body ground
2. Power management control ECU
3. Compressor with motor assembly
4. No. 2 engine wire (harness or connector
between compressor with motor assembly and
inverter with converter assembly)
5. Electric vehicle fuse
6. CAN communication system
7. Hybrid control system

 

Hi ,

It looks asif AzWxGuy may have only quoted from the "diagnostic trouble code chart" at the front of the A/C section in the manual. When you flip to the actual codes later in the section, there are five pages of troubleshooting info for /71, one page for /74, and nine pages for /98.

This is a Gen 3, where the compressor itself contains its own inverter (it just gets straight DC power from the traction battery, gets its own marching orders from the A/C "amplifier" ECU, and inverts the power locally to three-phase to drive its own motor). This is different from Gen 2, where the inverter/motor controls were all included in the main inverter box, and the compressor only had the motor.

So there is both a heavy, orange, high-voltage connector to the compressor itself, and a multi-pin, low voltage, marching-orders-and-status connector. That low voltage one could stand to be unplugged, maybe shot with some contact cleaner, and plugged in and out a couple times, then back in. Do not handle the orange, high-voltage plug at all, unless you first pull the service plug in the back of the car and wait 10 minutes. You could even do that before handling the other connector, depending on how you feel about working that close to the HV one.

I seem to recall another thread recently where poor connection quality in that low-voltage signal connector turned out to be the issue, and cleaning it up led to resolution. Our cars are getting about that age now....

If that doesn't solve it easily, I recommend the fifteen pages of troubleshooting procedures in the manual for further exploration.

-Chap

 

Thanks for the "further investigative" Chap. I figured I'd get it started, and as I alluded to I personally would not be monkeying around any further. High DC voltages are something to avoid. Correct me if I'm wrong though, wouldn't all HV lines be off when the vehicle is off?

 

That's the plan. Toyota still puts the service plug there anyway, and asks people to please use it. To make sure there's more than just one set of possibly-worn relays between you and the zoobs.

-Chap

 

Correct me if I’m wrong, the other wire (equivalent to the neg in DC or the neutral in AC) is well forward in the car and also safer with the relays. It is virtually impossible to either burn yourself with DC or electrocution with HV AC. The only chassis ground is the 12 V battery. A good worker always has his meter standing by to check dubious points. Or still charged capacitors.

 

The rule for any electrical work is to kill power at the source.

 

But, where is the source?

 

The orange plug on the HV battery. At 12:25 on this video.

 

WOW, we get all that voltage from just that little orange plug.

 

Actually the inverter converter increases the DC voltage another 2-300 volts AC to run the drive motors.

I don't understand how people can go inside that 200 volt battery without proper safety equipment.
You don't do it in your home electrical main box do you, high voltage is high voltage.

 

These companies have incorporated some good features. I agree with you, especially when the innocent thinks he can touch anything. But, saying this, one is safe if: the orange plug is removed, totally. With an effort one might span one leg of the battery pack, I understand the result is a warmth or burning, but not a electrocution. Either way I would not try it. But, I believe all do it yourself er’s are instinctively careful.

 

That's true if no alternative current path has developed within the battery. Tracks of leaked electrolyte in there, or malachite crystal formations around terminals growing toward the case, or stuff in gunky air from industrial neighborhoods drawn in by the battery fan, etc., can all play with that assumption. The battery ECU does perform constant checks for isolation faults, so most of the time, if it hasn't told you there's an isolation fault, you can go ahead and assume that pulling the service plug makes everything safe. As long as you're confident the ECU is working right, and nothing is wrong in its fault-sensing circuitry, so you trust its absence of a specific warning.

It's kind of the same story with the main relays that are supposed to isolate both sides of the battery output from the cabling to the rest of the car, whenever it is not READY. The ECU does, in fact, monitor all three relays, and will normally give you codes if a relay seems to be stuck or malfunctioning, so as long as you're willing to put your eggs in that basket, and it hasn't warned you of a problem, you could go ahead and assume there's no risk to you up front at the A/C supply, as long as the car isn't READY (and hasn't been, for long enough for stored voltages to bleed off).

Or you can just pull the service plug routinely, and that's the approach Toyota recommends, rather than going through a whole long checklist of why you're sure you're safe skipping that step. Nobody's giving out points for winning a game of chicken with the battery, and the battery doesn't care.

There are ranges of outcomes. While a lot of conversation on PriusChat focuses on shock risk, high voltage DC has other tricks too. There was an interesting presentation on how the NFPA 70E safety standard was getting revised for more relevance to DC and battery systems, with a good coverage of arc flash risk, noting that almost all the funding and study of that topic has been for AC systems, and the knowledge of what's appropriately safe for DC is about where the AC knowledge was 20 years ago.

I needed a good dose of optimism. I've read some posts over the years right here on PriusChat from folks describing how they approached a task, that were only missing the words HOLD MY BEER AND WATCH THIS to become truly timeless.

-Chap

 

I am reminded when working with any DC to become a one-handed electrician. This avoids providing a path for the current across your cardiac regions. Also note the heavy rubber gloves recommended in the Toyota repair manuals when working around high voltage DC. Better safe than sorry.

 

That one hand rule has always been encouraged when working on a live systems, DC or AC.. I think the technology has now advanced so far that test points may now be non-existent. Hopefully nobody is working on a Prius while the car is in ready. Years ago I worked on small engines and the hanger air hovered around 32F plus big breezes whenever the hanger doors were opened. So, if one did not wear gloves, the fingers froze and work stopped, Put on the gloves and all dexterity went out the window. Working on the Prius would be the same, just overkill with big, heavy and awkward High voltage gloves. Pulling the plug and keeping your voltmeter handy should be sufficient, for safety.

 

Chapman your inputs are always so interesting. The Prius Hybrid has now been around almost 20 years and thus far Iv heard of none of these speculations occurring. But interesting to contemplate. I remember years ago in elementary school being angry at a teacher that refused to teach Mushrooms. Of course it was the MA board of Education making that decision. If it’s dangerous stay away from it! and that’s it. With that philosophy we never would have gone to the moon.

 

We now know that flying in a rocket is dangerous, yet people do it and die. They know the risk and take it.
I applaud and Thank the Astronauts. Columbus was also an explorer and probably took much more risk than our Spacemen, no maps, no accurate directionality, a totally flakey little ship. We on the other hand don’t need to take ANY risk when working on our Prius, just remove the orange PLUGS.
( I always try to keep my posts in context)