tutz724

Hey everyone.

I have a 2001 DX I've been chasing AC problems on, and thought I was making some good progress on and even thought I had it all fixed.

Well, buttoned up everything last night and vacuumed and charged the system and was pleased to feel cold air coming from vents.

The problem? I was making visual checks and see the compressor clutch is not disengaging unless I either pull the relay or disconnect the pressure switch. The original problem was that the compressor burned up.

So this is a new compressor that won't disengage. My pressures are low on both low and high side, and the suction line is frosting. I'm starting to wonder if the problem lies deeper than charge.

I pulled the center control panel and disconnected the AC control switch and this did not disengage the compressor either.

Any insight is helpful. Thanks.

Feel free to ask questions to get a better picture as I'm sure I left out specifics that will help.

tutz724

A few other pieces of information:

Pulled a vacuum at 30inHg and that held for an hour. Also I charged the system and have the proper amount of charge.

sumdewd

By "locked up" you mean the compressor clutch won't disengage?

Do you still have 12v at the compressor's red wire when you pull the relay or disconnect the pressure switch?

tutz724

Yeah. Locked up was the only phrase that came to mind, but yes, the clutch doesn't disengage. Even with the AC system turned off the compressor keeps running. I saw the defrost thing, but this isn't even in defrost. This is with max AC and on face vents only. Either way I reprogrammed the ecu to not do the dedrost thing and it didn't help.

I'll have to check the voltage later this week as I'm coming up on work, but I would assume with the kreasupr switch disconnected I have 0 volts at the compressor since that is the last connection before the compressor is isolated. With the relay pulled I'll have to check.

Also, exact pressures running are 17 suction, 65-70 liquid. Static is about 41 @ ~55°F. Running pressures are also ~50/55°F. This would say that the charge is low, but I put probably 20oz, which is a tad much. I'll recover if necessary.

Again, there's about a 15° drop in temp at the vent, windows down.

My only concern is that I'm going to burn another compressor up. I'm puzzled. Everything points toward a leak and low charge, but then the temp is dropping as it should and the compressor is constantly running, which should not indicate low charge.

sumdewd

Look up too little clutch air gap. The symptoms you describe emulate it exactly. You'll have to crawl under the car, remove the 14mm(??) center hub nut, then add a shim(s) and re-test. You may have to visit a junkyard for more shims. I just start stockpiling them to be honest.

How cold is it outside? The pressure of a condensible is directly proportionate to outside temperature. We're in the dead of winter where I am, so don't expect higher pressures for a while.

Here is the procedure:




You'll know you have it adjusted correctly when the compressor can be commanded on and off, and it doesn't try to shut off and stop cooling when the car gets fully warmed up or if it's really hot outside.

tutz724

I will check this tonight after work and see what I find. I'm really hoping this is the issue. And yeah. The pressures being low was probably due to low temps. I have a propane heat source in the garage and the temp in the engine bay was 55-60 degrees F.

Any lead on shims other than a junkyard? Like where I can order? Is there any reason a regular old flat washer wouldn't work?

Thanks

1999 Civic Si

You should be able to order shims from a dealer, for example when I replaced the field coil and clutch on my 05 TL it came with 6 shims, but when I was looking at the parts diagram while ordering I could get them separately as well. You more than likely will not be able to get away with a flat washer, since the specs for the air gap are so small, finding a flat washer off the shelf that thin is more than likely not going to happen. Although the shims are basically flat washers. lol

Something else to check is to make sure your relay that provides power to the field coil (what activates the clutch) isn't stuck on. That is somewhat common in the older MDXs & some TLs.

tutz724

So I just happened to think of something. I'm going to check the clearance anyway to see, but wouldn't it stand to reason that if the clutch disengages when the relay and pressure switch are pulled that the tolerance should be enough to allow the clutch to disengage? Just keeping discussion going.

Also on the relay, I have swapped relays and the problem persists.

Gonna dive pretty deep into this this weekend and I'll let you all know what I find.

sumdewd

Exactly. It is an electromagnetic clutch that uses a field coil to create a magnetic field strong enough to lock the outer hub to the pulley, which engages the compressor. If the gap is correct, pulling the switch or relay would cause it to disengage and shut off. If the tolerance is too little, it will always be mechanically engaged. Too loose and it will turn off when hot, or never turn on.

Ryanthegreat1

You swap relays yet? This generation is pretty common to stick relays closed. Swap it with the horn relay, should be the same.

tutz724

So....

Let me tell you what I have right now:

AC compressor relay voltages. Key off:

Pin terminal
​​​85: 0
86: 0
30: 0
87: ~13.6

Car running with or without AC switch "on":
85: ~14.5
86: 0
30: 0
87: ~14.5

So it looks to me like the relay is energized at all times regardless of AC switch position.

I'm starting to think ECU? Thoughts?

sumdewd

Does pulling the relay make a change in the A/C compressor engaging/disengaging? Does it click at all when you plug it in and toggle A/C? You can also try grounding 85 and applying power to 86 to see if it clicks on and off.

tutz724

Yeah. You pull it and the compressor clutch disengages. Put it in and compressor clutch is engaged all the time.

Also hooked up 12V to it and audibly heard the click.

Is it possible that the AC comlrecomp clutch is the only thing affected by a bad ECU?

I guess I have one other electrical problem and that's the coolant gauge only rises to temp when you drive. You can sit at idle for an hour and it won't budge the needle at all until you accelerate. Maybe another side effect of a bad ECU?

tutz724

I do notice that in the manual it states that 0V at the ACC pin on the ECU connector (the one for the AC clutch) means on and battery voltage means off.

I haven't stuck it, but it would stand to reason that the ECU is either doing it's job and there is 0V drop across it and the switch is shorted closed, or it's just flat not getting voltage from the switch and, again, the switch is inoperable.

Or am I not seeing that correctly?

Ryanthegreat1

Did you swap relays?

Nothing wrong with the voltages you measured. The relay is ground switched. There will always be 12v on the control side. The ECU grounds the the side when it requests AC. If you measured with the relay installed you would see 12v on both sides of the control when AC is off. Then when the ECU pulls that pin to ground you would see 12v and 0v.

With key off engine off does removing and inserting the relay still make the AC clutch clack? If yes, bad relay. If no bad ECU ground. Check the ground at the water neck.

tutz724

With the key off/engine off the relay does nothing. The ECM is grounded at G133, correct?

Ryanthegreat1

Not sure, I don't have a manual for one of those.

Check for continuity to ground on 86 for the relay, should be open with AC off.

tutz724

Ok. Also how can I ground out the socket to see if that will stop the compressor?