AC Clutch workaround

[joedogg]

Hey all!

About 5 months ago my compressor clutch stopped engaging except for very rare occasions.

Starting to get hot again, so today I went in and tried jumping it directly to the battery. Engaged immediately. No problem whatsoever.

A multimeter told me I was still getting voltage through the appropriate wire, however it was no longer causing the clutch to actually engage. I assume it wasn't able to carry enough current.

As a work around I hooked the existing 12v that should go to the compressor clutch to a relay that will supply 12v directly from the battery when the old compressor wire gets a charge. Works great, no problem whatsoever.

Does anyone see a problem with using this as a permanent solution? Seems to me that this shouldn't really interfere with operation at all. I just wanted to check to get another opinion about just leaving this as is.

Thanks!

 

[CanadianSniper]

What year is this car? On a 97 if you open the hood and look to the left, If i remember just behind the rad there is a high pressure switch with two wires going to it! Pull the plug and jump these two wires and see if your compressor runs? Doing so will make your compressor run continuous so don't leave it this way. Sounds like you have either a bad high pressure swith of there is insufficient pressure to tell the switch to turn on the compresssor. A matter of maybe a few ounces! Hope this helps.

 

[shodoug]

That's really interesting. I doubt it should make much of a difference. At the worst it will burn out a clutch that isn't working anyway, but I doubt the small difference will do that.

Since it runs off a relay that is pulled in by the wire that originally went the clutch, ( if I understand you correctly) then there is no indication to me that any of the switches are bad.

Have you done the shim-ectomy on this AC yet? Maybe I should do a relay in addition to my shimectomy on my car. If it makes it pull in tighter, it might make it lock up better and last longer.

Doug

 

[Izzmo]

The only part I wonder about this is I think you are bypassing safety measures.. so lets say if you do not have enough freeon (pressure) in the system, then you are still engaging the compressor, which could eventually do damage.

But I may be wrong.

 

[shodoug]

The only part I wonder about this is I think you are bypassing safety measures.. so lets say if you do not have enough freeon (pressure) in the system, then you are still engaging the compressor, which could eventually do damage.

But I may be wrong.

From what I understand, originally he tested by hooking a wire directly from the battery to the clutch.

This worked, so he thought it might have been the higher, unregulated battery voltage that gave enough of a boost that the clutch coil pulled in and made the ac compressor spun. ( or possibly the voltage increase in conjunction with a lower voltage drop over a larger {and possibly shorter} wire)

Then, he went on to change the way he applied the battery voltage.

He pulled the wire that originally energized the clutch and ran it to a relay.

The relay switched battery voltage to the clutch, possibly over a larger wire than stock, when the clutch wire would have normally been hot. So, now, the interlock switches are all fully functional, since they will prevent the wire that used to go to the clutch from getting hot if there is a problem. Then the relay will not turn on, and the clutch will not engage.

Of course, I could have been the one that misunderstood what he did.

It is easier than the first shimectomy I did. Maybe it wil make a shimectomy last longer, too. If it makes the clutch pull in better, it might even lessen clutch wear???

Doug

 

[Izzmo]

Right, I believe he is essentially "jumping" the terminals to get the clutch to come on when he wants though right? Maybe I am looking at this wrong, but from what he said (and you, shodoug) said, it seems he is doing this trick.

 

[SHOZ123]

The PCM tells the AC clutch relay to come on. It then compresses the freon until the pressure builds and the high pressure switch opens. Then the clutch turns off (the OEM relay is still in the on mode) until the pressure reduces from it being converted from a gas to a liquid from absorbing heat and the high pressure switch again closes. This is the typical cycling, if the ambient temps are high enough it will just stay on as the pressure never gets high enough to open the high pressure switch and cycle.

The low pressure switch will **** the clutch power too. But unless you charge the system or it is so marginally low that the pressure rises enough from ambient temps it will not come on.

Forcing the clutch on by bypassing either the low or high pressure switches is a sure way to destroy the compressor.

 

[shodoug]

Right, and from what I understood, he is still using all that logic, because he is using the original wire that came from the original clutch, to trigger a separate relay instead of engaging the clutch.

The separate relay switches battery voltage instead of whatever the original relay was sending to the clutch. It also uses a different wire, so the gauge and length is probably different.

I get that impression from this paragraph on his post...

"As a work around I hooked the existing 12v that should go to the compressor clutch to a relay that will supply 12v directly from the battery when the old compressor wire gets a charge. Works great, no problem whatsoever."

If we think of that original relay that gave power to the AC clutch as being a relay that is internal to a PLC, called "DO1," then he has added an external, interposing relay that is triggered by the DO1 output from the PLC, so any logic and any interlocks that are used to enable/disable DO1 will also enable/disable his relay. He is just switching from a higher voltage power source, in perfect sync with the original logic that controlled the clutch.

Basically, he did the same thing that I did, when I took the power wire to my headlights and ran it to relay that switched battery voltage to my headlights. Only he did it with his AC clutch. ( many other have done that with the headlight signal, and I mainly followed Paul Nimz's lead on that one, BTW)

Again, that is how I understood what he did. Since I seem to be alone on this, I could certainly be wrong.

However if I am not wrong, it is very interesting to know that using battery voltage ( and possible a shorter, fatter wire) allowed hos non-functioning clutch to work.

Just as it was interesting to see in another thread that using a larger gauge wire for one of the conductors in a 98 allowed the speedometer to work over 115, in at least two cars.

Best Regards,
Doug

 

[Izzmo]

Oh, good description shodoug. That makes sense now. If what you say is correct, I would think what he is doing should work then.

 

[SHOZ123]

If you power the clutch directly from another 12V source at the AC clutch connector then you are bypassing the high and low pressure switches.

If the CCRM relay for the AC is bad then the work around would be good as long as you intercept the wire before the switches. If the separately mounted relay for the +98's is bad then just replace it.

After looking at the wire diagram a bit closer this is how it is suppose to work.

The Integrated Control Panel (football) tells the Remote Climate Control module to send a signal though the low pressure switch AKA cycling switch on the purple wire. The cycling switch closes at 45 psi and opens at 23.5 psi. When closed it goes to the high pressure switch on the red/yellow wire and passes on to the PCM (as an input) and CCRM to turn on the AC relay using the dark green/white wire.

If you are going to safely switch the AC clutch it needs to be done through the purple wire.

 

[joedogg]

Okay, sorry took so long to reply to this.

There are 2 wires going into the AC compressor. There is the power and the ground.

If the power wire is activated by whatever array of switches and sensors then it will send 12v to the AC clutch so it will activate.

All I did was take that power wire and hook it to the switch on a relay. The effect being that if the AC compressor is being told to turn on, it will activate this relay which will supply 12V directly from the battery cable connected to the underhood fuse block.

My understanding of it is that any switch or sensor that does not want the AC engaged will have interrupted the flow of power before it gets to my relay. Therefore, my relay won't close and the power will not get to the compressor.

So, I think that nothing has been bypassed.

 

[SHOZ123]

I guess I don't understand why if you have power and ground at the AC clutch connector are you providing an alternative source controlled by the first.

 

[Daedalus]

My thought upon reading your original post is that you may need to remove your AC clutch shim. Sounds like with the "standard" current you don't have quite enough juice to engage the clutch, but while taking power straight from the charging system you get enough extra to just pull the clutch tight.

Just a thought. Removing the clutch shim from my car fixed my AC clutch non-engagement issues.

 

[joedogg]

My thought upon reading your original post is that you may need to remove your AC clutch shim. Sounds like with the "standard" current you don't have quite enough juice to engage the clutch, but while taking power straight from the charging system you get enough extra to just pull the clutch tight.

Just a thought. Removing the clutch shim from my car fixed my AC clutch non-engagement issues.

That's exactly whats going on, I think. I remember when it was going out, I opened the hood and could see the AC "trying to engage." The clutch was moving very slowly and just couldn't quite lock on. By providing the extra kick it locks right up.

How does one go about this? I read the guide on v8sho.com and I'm pretty lost as to what they're talking about. Am I just gathering that the clutch is too wide and needs to be tightened down?

 

[SHOZ123]

I used an impact wrench with a long wobble bit extension. Got to it from the wheel well. Took longer to R&R the wheel and fender liner than to remove the shim.

Just take the nut off, remove pulley and remove the very thin shim. Put back together.

Mine use to not engage when at higher rpms. At highway speeds if it was off it would not come on. But if at idle it would. Removing the shim made it work correctly all the time.

 

[joedogg]

Ohh, so I gather you outright remove this "shim" and put it back together without it. Then it should be good to go without my relay gig.

Okay, that doesn't sound too horrendous. I'm going to go re-read that with this as the understanding to see if it makes any more sense now.

 

[Izzmo]

Btw... it's just a washer. Everyone calls it a shim.. but I just call it what it is. (Just in case you are wondering what to pull out)

 

[Daedalus]

^ What he said.

I think the V8SHO.com instructions for this issue are not very helpful, and call for an awful lot of extra, unnecessary work. Here's how I removed mine. If I remember correctly, you do not need to remove the serpentine belt in order to do this.

1. Jack up front of car, put jackstands under the framerails.
2. Remove passenger side tire.
3. Remove large plastic deflector under the radiator.
4. Remove plastic splash shield from passenger wheel well.
5. Put jack underneath passenger side subframe and raise jack to remove all slack.
6. Remove front and rear passenger side subframe bolts.
7. Gently lower the passenger side of the subframe using the jack until you can see the bolt in the center of the A/C pulley. You may have to unbolt the power steering reservoir from the strut tower in order to lower the subframe this far (I cracked my reservoir doing this, by not being careful).
8. Using a 14mm socket, remove the bolt from the center of the A/C compressor pulley. I didn't have a socket small enough to fit inside the lip, so I ended up using a grinder on the outside of a cheap socket until it would fit.
9. Remove the outer clutch assembly from the pulley. It should just pull straight off. The pulley will remain on the compressor.
10. Find and discard the "shim," a small brass-colored washer.
11. Reinstall the clutch assembly and replace the 14mm bolt.
12. [Optional] Check that the gap between the clutch and the pulley is at least .3mm.
13. Raise the subframe with the jack and reinstall the bolts.
14. Reinstall the splash shield in the passenger wheel well.
15. Reinstall the passenger side wheel.
16. Lower the car to the ground.
17. Torque the subframe bolts with the car on the ground. I don't recall the proper torque value off the top of my head.
18. Reinstall the big plastic splitter under the radiator.
19. Enjoy ice-cold air!

 

[joedogg]

Thanks guys! I'm pretty sure this is exactly the problem, I'll give it a try this weekend, and see what happens by connecting the original wire back.