07 Prius Air Conditioner Randomly Quits.

[treyi]

Last summer the air conditioner in my 07 Prius started quitting for no reason. It only does it every so often and seeming only when it is warm out. I didn't have any trouble with it in the winter I can recall. None of the fan speeds work and I can not tell if it is just the fan or the entire A/C system. I thought it might be a short or loose connection so I decided to shake it around a little by driving on the lane divider bumps but no luck. Yesterday it did it twice and came back on as strange as it went off.

Last summer I scheduled a service appointment and by that time it was working again. They couldn't find anything and in a few weeks it quit again. This time I took it to the dealer while it was not working just so one of the service guys could see it was not working. I had to schedule another appointment. This time they said the main screen might need to be replaced. The ordered it and allegedly replaced it. I suspect they may not have since the screen still had the same finger prints on it when I got it back. I think they just said that to pacify me, but that is another story.

Any suggestions would be greatly appreciated.

Thanks,
Trey

[jayman]

Originally Posted by treyi

This time they said the main screen might need to be replaced. The ordered it and allegedly replaced it.

I hope that was warranty, it's a pricey part otherwise

Did they cover the basics? Eg, system charge?

[treyi]

It was. And I think they checked the pressure and everything. Last summer when it worked it worked great. Even with the temperature outside over 100 degrees. I would think if the charge was low it would not preform very well.

[jayman]

Could be a loose connector. We've had debates in other threads about loose connectors and garbled CAN/LIN/BEAN messaging.

If still under warranty, I'd suggest a stop by the dealership. I know it's difficult to get these things to act up WHEN you want them too

[yardman 49]

Originally Posted by jayman

Could be a loose connector. We've had debates in other threads about loose connectors and garbled CAN/LIN/BEAN messaging.

If still under warranty, I'd suggest a stop by the dealership. I know it's difficult to get these things to act up WHEN you want them too

I concur, for what it's worth. Loose CAN bus connections between devices, loose terminators, bus failures inside of devices, can all contribute to CAN comm problems.

We use the CAN bus protocol on some equipment made by my company. We have diagnostics tests for these to be certain that the linked modules are healthy, and the comms are working properly. I would assume that auto manufacturers would have CAN diagnostics tools available to their service departments?

[jayman]

Frank

You mean like a MSO or VSA? No, I wouldn't assume that at all. Not knocking service techs at dealerships, but it takes a wee bit of skill and understanding to properly use and interpret a MSO/VSA.

Eg, here are some glitches I uncovered on a CANBus problem. I used an Agilent MSO with deep memory, and auto-trigger on glitch



I've outlined the glitch



The effect of randomized noise



Here the MSO triggered on a PW glitch



I would think at a service level, it would be better to just carefully unseat and reseat all the connectors. We've had this discussion of weird combination meter "failures" that may, in fact, be caused by minute amounts of connector corrosion

jay

[yardman 49]

Originally Posted by jayman

Frank

You mean like a MSO or VSA? No, I wouldn't assume that at all. Not knocking service techs at dealerships, but it takes a wee bit of skill and understanding to properly use and interpret a MSO/VSA.

I would think at a service level, it would be better to just carefully unseat and reseat all the connectors. We've had this discussion of weird combination meter "failures" that may, in fact, be caused by minute amounts of connector corrosion

jay

Hello Jay:

I don't really know what an auto manufacturer would train their service techs on for more in-depth troubleshooting. I've never used an MSO or VSA. The most I get to play with is a humble Tektronix THS730a. I was thinking more along the line of a PC based digitizer and some specifically written proprietary diagnostics software, that would exercise modules and look for responses.

I use digital scopes for pulse circuit troubleshooting, but not on CAN problems. Our CAN diagnostics are pretty simplistic, simply looking for pings and module ID responses from the devices on the bus. I've used the "CANscope" software for this before; but we also had a programmer in the past that wrote some code for us in NI LabVIEW. That's pretty much all we've come to rely on. Not really good enough too look at noise on the bus, but rather "is is talking or not"?

One issue that I check for is for the terminator at the end of the bus that we use. That has caused weird (intermittent) problems in the past if it wasn't attached securely. Other than a connection, when we lose the CAN communication in one of our modules, it's usually because of a power arc that takes down more than just the CANBus

Nice traces! Thanks for the pictures.

[jayman]

Frank

I completely agree it would be great to have a purpose-built tester. I realize that CANBus is fairly new for automotive fleets, but as that fleet ages, we can expect to uncover a lot of issues

Eg the combi meter "problem" in earlier 2004-2006 Prius cars. It's widely reported that replacing the +$1,500 combi meter reliably "fixes" the problem. I'm wondering if just the act of unseating and then reseating all four bus connectors also fixes the problem, and replacing the combi meter is completely unnecessary

I completely agree that terminator issues can play a big - important - part in diagnostics. Anything that can introduce randomized glitches deserves more attention, and I'm afraid the "replace parts until it works again" approach is the WRONG approach here

The Agilent I used was the slightly older brother to the InfiniiVision 6054A. It will automatically trigger on glitch, or any other parameter you chose. Overall a very smart MSO, as it should be for +$15,000.

You can also have the MSO capture the entire screen and save it internally, or on the network, as a JPEG. I find this a very useful feature when discussing errors and glitches with clients.

jay

[treyi]

I took it back to the dealer day before yesterday and they kept it for 2 days. They said they checked all the connections and wires and found nothing. They want to replace the "screen" again. Now they are saying my radar detector could be causing the problem, which I don't buy at all. It is wired into the lighter circuit which they claim is different than plugging it in because it causes a "current split" and could be causing my "screen" to go bad thus making my A/C quit. I think my B.S. limit has been reached. What does everyone else think?

[richard schumacher]

I think I have little sympathy for anyone who uses a radar detector :_>

But seriously, we have read here of cases in which aftermarket electronics caused weird and/or flaky problems. Sometimes the root cause was sloppy installation.