A/C problem with no code

Hi folks,

It's getting hot here in Wisconsin, and the A/C in our 2002 is completely nonfunctional (and has been since we bought it a year ago). Unfortunately it also doesn't provide a diagnostic code to point me in the right direction. So yet again, I'm turning to you all for ideas on where to begin.

When the A/C is turned on, the light begins flashing immediately, and the air is not cold. I've tried it while the engine is at high RPMs, and idling in the driveway with no change in results. When I put it in diagnostic mode there still aren't any codes (except the solar sensor if it is dark).

If the ICE is off when I turn on the A/C, the ICE fires up briefly then shuts down.

The mechanic we bought it from suspected the compressor. I hoped it was really the clutch (seems common), and that I could just put in shims to adjust the spacing.

The only code I have gotten from it was for the cabin air intake servo motor shortly after we bought it. I found a mouse nest in the cabin air filter, which I figured was causing the problem. After replacing the filter the code went away but the A/C still wouldn't work.

I'm wondering..

Is there anything else I can do to trigger a DTC? Are there any specific problems that wouldn't have a DTC?

Would a compressor/clutch problem certainly trigger a DTC? Can I test it when there is no functionality? (It seems more common to have intermittent trouble with that)

If some of the mouse nest was sucked into the A/C system, could it cause this?

Thanks for your time.

 

I did a little exploratory surgery today.

The cabin air filter had a lot of debris stuck in it, so I brushed it off. There were some leaves that had gotten past the filter (perhaps from last time) so I expect some debris did get through. But the fan works fine, and the servo motor opens and closes the damper fine.

I poked around the A/C clutch a bit. I watched it as the A/C was turned on and didn't see any movement. I did notice, however, that the outermost plate (the pressure plate?) appears bent. I'm still studying my clutch anatomy, so I'm not sure how much to make of that. The maximum gap between that plate and the pulley is over a millimeter, well beyond the .5mm specified by Toyota. I made a video of it spinning.. View My Video

The clutch is my main suspect at the moment, but the lack of a DTC bothers me. From what I understand there is a code for when the compressor doesn't rotate at the expected speed when the clutch is engaged. I would expect that code if the compressor doesn't spin at all..

I might try testing the clutch, first by checking that the magnet gets power when the A/C is turned on, and then by supplying 12v directly to it to see if the clutch engages (and if it engages with 12v and a push).

 

The plot thickens..

I popped off the connector to the A/C clutch and found that there isn't power applied to the clutch when the A/C is turned on. I checked it with two different multitesters, then pulled the wires out and checked again. There is a good conduction to ground, but no power.

To me that means either the car tries to engage and can't (bad connection somewhere or a safety switch is opening the circuit), or some other sensor is indicating a problem somewhere else and the car doesn't try to engage the clutch.

On top of that, the clutch is in rough shape. With 12v applied the pressure plate twitches but doesn't really engage. Even when I push by hand as well it only partially connects, and I can still spin it easily.

I've resigned myself to replacing the clutch, and it's time for a new serpentine belt anyway. But I'm not confident that will resolve the problem.

I'll try to find a wiring diagram.. I assume there is a freon low pressure switch, that might be my next stop. Though I would expect a code from that as well..

Chime in if you have ideas, I'm stabbing in the dark here.

 

Thanks Chap,

That relay gets power for about a second when the A/C is turned on. I tested the relay, it works fine.

I got a 2 day subscription to techinfo.toyota.com, which has helped a lot. It had me check the compressor lock sensor. I read .25 ohms from pins 2 and 4, the spec is 160-320. The solution offered is replacing the compressor. Eek!

I'm confused about 'compressor lock', and what that refers to. Step 1 (before checking the sensor) was 'Check if the compressor does not lock during operation..'. Is 'locking' the clutch engaging? Or the compressor locking up? Or is it just referring to when DTC 22 occurs?

Thanks again.

 

And the dual pressure switch tested fine, so I'm scratching that off the list.

 

Annoying surprise indeed. I pulled off the sensor and got blasted in the face with refrigerant! If anyone else is poking around in there, be aware: the compressor lock sensor is under pressure. I wore safety glasses all day, except when removing the one thing I knew could be under pressure. Sheesh. Fortunately after a good eye flushing, I think I'm fine.

I don't think it vented out the system, but it may have (there go all my environmentalist credits). I could see the compressor shaft inside, hopefully the internal seals kept all but a small pocket inside. I'll check the pressure switch tomorrow to see if it fell out of range.

Anyway, that sensor is bad. I poked the wires at the sensor and got the same .25 reading as before. As you said, Chap, no one seems to sell the sensor. If I can find one though, it might just solve the problem (assuming I haven't created a larger one).

I also pulled the clutch off. There was only one washer in there, it's about 1mm thick. It seems I'm not the first to adjust it. Since the plate was about 1mm past spec, I'll just reinstall without the washer and see if that does it. Oriely's couldn't get me the shim kit, they said Toyota had "locked down" that part.

I'm taking my mildly irritated eyes to bed. Tomorrow I'll reinstall the clutch and a new serpentine belt. Until I can find that sensor we'll just have to roll down the windows.

 

Everything seems fine. I had the same thought about moisture and put the sensor back after I tested it.

The pressure switch didn't drop out of range, so I'm fairly certain it was just a pocket of compressed refrigerant I let out. If a person knew about it before hand they could pull the sensor out safely. Just don't crawl under the car and stick your face next to it.

I cleaned up and reassembled the clutch. A few extra thin washers I had laying around got it to the perfect spacing. I engaged it with a spare battery and it locked down great.

The hunt for the sensor begins..

P.S. While I had access to tech.toyota I downloaded the repair manual. It was a chore to do it (nearly page by page) but that thing is a treasure trove.

 

Yes and yes. There weren't any for sale, but I contacted a half a dozen eBay sellers who had Prius compressors. A few had them.. the lowest price I was offered was $20 (10 for sensor, 10 for shipping) from Jensen Auto Inc on the east coast USA. It hasn't arrived yet. I was actually quoted $30, but the person I talked to said $20 and I didn't object.

The sensor does have an O-ring. I'd be happy to measure it next time I have it pulled out of the car (looks like early next week).

It's leaking oil, you say? I know there is some oil in the refrigerant.. I wonder how that is oozing out. Are you losing refrigerant pressure too?

My face did feel a bit oily afterwards

 

Well, I got the sensor today. I tested it and got .248 K Ohms (248 Ohms). I had a sickening feeling when I saw that because I realized I had misread my multimeter when I tested the original! It wasn't .250 Ohms, it was 250 Ohms. Another test confirmed my error.

Ohm my goodness that was silly!

I swapped them out anyway, and for some reason the AC is marginally better. Instead of flashing as soon as it is turned on, the AC light stays solid. Even took it for a drive and it stayed on, as does the MAX light. The air coming out seems to be ambient temperature though. But here's the odd thing: the clutch still isn't engaging. But instead of flashing the light, the car acts like it is doing a great job of keeping me cool.

I'm going back to the manual to see what else could be interrupting power to the clutch.

This isn't by-the-book, but I wondered about manually engaging the clutch with another battery while the engine is running to see if the clutch can do its job and if that gets some cold air coming out. I now have two wiring harnesses, so it'd be an easy test. I don't want to cause any damage, is there anything else in the AC system that could be damaged by the compressor engaging when it might not be expected?

I've attached a pic of the O-ring, I'll let you interpret the size, Mch.

 

And the sensor looks like this.

There was a much smaller release of gas this time, supporting the theory that it gradually builds up by slipping past the internal seals.

 

Okay, I'm not sure what make of this:

I bypassed the relay by running a wire between the large blades (one of which has 13v) and the clutch does not engage.

I went one step further and jumpered the hot terminal to the clutch connector pulled from my old sensor. I ran the other clutch wire to ground. When I completed the circuit the clutch locked down great and the compressor spun.

Seems like there's a problem between the relay and the clutch.. I'll redo the test tomorrow to be sure.

Revisiting my previous relay test seems like a great idea. I had an assistant turn the AC on and off while watching the smaller pins with my multitester. I'm not sure what to look for, but there wasn't any voltage between them at any point. One of the pins has 13v (to ground) as long as the car is on. Does the other make a ground connection to engage the relay?

Swapping the relay with the one for the horn had no effect either (same numbers on them).

I did the LED test too, and it didn't light up. But it's fairly cool now, would the AC amplifier still engage the relay?

I'll redo all the tests tomorrow when it is hot and well-lit. These tests seem to point in two different directions (wiring from relay to clutch/ AC amplifier not engaging the relay). But I can't rule out human error, as evidenced by my blunders so far.

Glad you found an O-ring, Mch. Hope it seals the leak.

 

No change today. I jumped the big slots of the relay connector and the clutch did not engage.

I checked for continuity from the relay connector to the clutch connector and also to the larger compressor connector where it joins the wires from the sensor. Nothing.

Double checked the ground, good.

Double checked for voltage between the smaller relay blades when AC is turned on, nothing.

If I'm reading the wiring diagram correctly, it is a straight shot from that relay to the clutch connector. So the fact that there is no continuity is a matter of a broken wire, loose connector, etc.

I don't know what to make of the fact that the amplifier does not engage the relay. There is supposed to be a DTC if the amplifier is acting up (22), otherwise I'd suspect that.

Maybe I'm in over my head.

I manually engaged the clutch and ran the car for a while, curious if it would cool the cabin. The air certainly wasn't cold, I couldn't tell if it was cooler than ambient. I left the wiring in place to try again at peak heat tomorrow.

I even wondered if charged up the AC and wired a switch for the clutch if I could get some cold air manually. Obviously I'd be risking roasting my serpentine belt if the compressor ever locked up.. But aside from servo motors directing airflow (which seem to react when I adjust the controls) the compressor is the only active component in the system..