A/C Compressor clutch

[DMC3165]

I have had A/C issues for a little while now. The system is holding a charge and everything appears to be working but it's just not getting cold. However recently I've noticed rust seems to be flying out of my compressor clutch and getting on the coolant hose and side of the engine bay. So i'm thinking the clutch is going bad. Is there anyway to replace the clutch on the vehicle without discharging my A/C system? It's currently charged with R-12 and I'd like to keep it. I looked on DMCH's website but only saw the compressor listed.

[Ron]

If your clutch is bad, you can change it out, but it takes special tools, which you may be able to borrow from the autoparts.

See Resource Section- Sanden Service Manual, 10.4 Clutch Inspection (http://dmctalk.org/showthread.php?353-Sanden-SD-AC-Compressor-Service-Manual)

Search for several other threads on the subject too...

[DavidProehl]

If DMCH doesn't sell it, you can get it from Hervey:

http://www.specialtauto.com/delorean-parts/AC-Cooling.html

21073

[Henrik]

I have had A/C issues for a little while now. The system is holding a charge and everything appears to be working but it's just not getting cold. However recently I've noticed rust seems to be flying out of my compressor clutch and getting on the coolant hose and side of the engine bay. So i'm thinking the clutch is going bad. Is there anyway to replace the clutch on the vehicle without discharging my A/C system? It's currently charged with R-12 and I'd like to keep it. I looked on DMCH's website but only saw the compressor listed.

Hmmm... I am a little confused about the "rust" you are describing. I can see two possibilities:

1) If the "rust" is being slung all over the place and is leaving a noticeable trail, then the problem might be a leaky lip seal (where the shaft goes through the body). In this scenario refrigerant/oil is ooozing out from the front of the compressor body and onto the clutch. Obviously, if the "rust" is oily, then this theory may be correct. However, you said the system is cooling well, and if there was oil on the clutch it would likely be slipping as well. So maybe not.

2) The "rust" you are seeing is sparking due to slippage between the armature ("front") plate and the rotor. And the slippage is due to an excessive air gap between the two. This is by far the most common failure mode for the clutch. You should take care of this asap because the slippage may cause the seal to overheat (side note: the old SD-5's mechanical seal is actually more heat tolerant than the (rubber) lip seal of today's SD-5s and SD-7s) and blow your charge. Section 10.4 shows that the gap needs to be 0.4 - 0.8 mm and is easily adjusted with shims between the armature plate and shaft (you'll see them once you remove the armature). You do not need to discharge the system but you should remove the compressor from the bracket to make room for the armature puller. Don't even think about using screw drivers:nono: Just follow section 14 of the Service Manual.

[Silverbullet]

Ok, I had great cooling for 15-20 minutes everytime I drove, system was charged... I finally discovered that the compressor could not pull the clutch in when it got hot. I checked the Air gap with a feeler gauge, and it was .052, it is spec to be .016-.031. So I removed a shim (Washer) and now it is .024 and works great all the time. See http://dmctalk.org/showthread.php?7618-Ok-Think-I-fixed-the-AC

[Henrik]

Yep - you got to the root cause!

[DMC3165]

The rust is not oily. There is no indication there is Freon or oil leaking. While checking the system with pressure gauges everything reads exactly what it should. I will try to post a pic later. I didn't know the clutches were adjustable, or how to adjust the air gap for that matter. Also I said everything appears to be working properly it's just not getting cold inside. The only indication that there's anything wrong is the rust which lead me to a worn out clutch. Thanks for the info and the links.

[Silverbullet]

Ok, So is the clutch turning with the pully? if it is and not getting cold, the clutch is not the issue... Either bad compressor, blockage, or low charge. For the rust I would check the air gap, pull the clutch, and sand both sides to be clean. adjust the gap if needed. You really some gauges on it while it is running.

Craig

[Henrik]

The rust is not oily. There is no indication there is Freon or oil leaking. While checking the system with pressure gauges everything reads exactly what it should. I will try to post a pic later. I didn't know the clutches were adjustable, or how to adjust the air gap for that matter. Also I said everything appears to be working properly it's just not getting cold inside. The only indication that there's anything wrong is the rust which lead me to a worn out clutch. Thanks for the info and the links.

I feel like it would be easy to rule out the clutch if you could provide some more specifics around the "rust". Also, is the armature plate engaging (i.e. "pulling in") when you turn on the A/C? Why not just put 12V on the clutch wire with the engine off and find out? And if it engages, turn the armature with your hand and see if the rotor turns with it. Sure, there is no load on the A/C system at that point but at least it's a starting point. If the rotor is not turning then it is either excessive air gap or a faulty coil. Again, you should refer the Sanden service manual. It tells you all you need to know.

[DMC3165]

Actually just today (against everyone's advice) I adjusted my low pressure switch today and that greatly reduced the compressor cycling and the a/c was blowing much colder. May leave it for a bit and see what happens. I still think the rust was because the compressor was cycling to often prematurely wearing the clutch.

[Silverbullet]

Actually just today (against everyone's advice) I adjusted my low pressure switch today and that greatly reduced the compressor cycling and the a/c was blowing much colder. May leave it for a bit and see what happens. I still think the rust was because the compressor was cycling to often prematurely wearing the clutch.

I am not sure how wear and Rust go together... My guess would be it was rained on or got wet or really damp for a LONG time, and the cast iron...rusted... now you are useing it, and the rust is being thrown out.... but that is just my take... Mine had no rust at all.

Craig

[djdogbone]

Today, I turned over 5628 and I heard some chirping from the engine bay. After some snooping, I discovered one of the two pulleys for the AC belt tensioner locked up. I just had the compressor changed out.

Some PB Blaster loosened it up and I managed to get some WD40 in there and it's moving again.

Now, since I'm a new owner, my question is; how often to these little buggers fail?

I'm also going to replace the Motorola 90Amp With D110 alternator. Are there other mechanics prone to failure? Cooling fans are on my list.

In any case, I'm going to order a remanufactured replacement pulley from SpecialT.

[DMCMW Dave]

Today, I turned over 5628 and I heard some chirping from the engine bay. After some snooping, I discovered one of the two pulleys for the AC belt tensioner locked up. I just had the compressor changed out.

Some PB Blaster loosened it up and I managed to get some WD40 in there and it's moving again.

Now, since I'm a new owner, my question is; how often to these little buggers fail?

----.


They fail a lot. The bearing all by itself is less than $6. Be sure to replace both of them at the same time and look closely to make sure the belt didn't get smoked.

[Ratrace427]

Lets talk more about this low pressure switch adjustment. My knowledge goes as far as knowing it is on the dryer but how does one adjust it?

[dmc6960]

Lets talk more about this low pressure switch adjustment. My knowledge goes as far as knowing it is on the dryer but how does one adjust it?

Its the switch on the AC accumulator. You remove the harness plug to access the adjustment knob. NOT all switches are adjustable. You ONLY adjust it if its switching out of the proper range based off of readings from an AC gauge set.

See here (paragraphs 2 and 3)...
http://dmctalk.org/showthread.php?7728-Dangers-Associated-With-Freezing-The-Evaporator&p=113862&viewfull=1#post113862

Here...
http://dmctalk.org/showthread.php?7728-Dangers-Associated-With-Freezing-The-Evaporator&p=114520&viewfull=1#post114520

And Here...
http://delorean6575revisited.blogspot.com/2013/08/resurrecting-r12-ac-system-and.html

[David T]

[QUOTE=DMCMW Dave;116248]They fail a lot. The bearing all by itself is less than $6. Be sure to replace both of them at the same time and look closely to make sure the belt didn't get smoked.[/QUOTE

The venders will also recommend you replace the "O" ring under a cam cover behind one of the bearings. You have to be very careful to remove and replace all of the spacers, washers, and bolts correctly. Everything is "prone to failure" just some things last longer than others. As long as you are replacing the bearings and alternator you should also replace both belts and the upper right bracket for the muffler (the OE one is prone to cracking). If the seal for the crank pulley is leaking you might want to try to replace that. Be careful not to overtighten the belts. That will cause the idler bearings to fail quicker and if you overtighten the alternator you will damage the bearings in the water pump.
David Teitelbaum

[David T]

Its the switch on the AC accumulator. You remove the harness plug to access the adjustment knob. NOT all switches are adjustable. You ONLY adjust it if its switching out of the proper range based off of readings from an AC gauge set.

See here (paragraphs 2 and 3)...
http://dmctalk.org/showthread.php?7728-Dangers-Associated-With-Freezing-The-Evaporator&p=113862&viewfull=1#post113862

Here...
http://dmctalk.org/showthread.php?7728-Dangers-Associated-With-Freezing-The-Evaporator&p=114520&viewfull=1#post114520

And Here...
http://delorean6575revisited.blogspot.com/2013/08/resurrecting-r12-ac-system-and.html

Typically you should never touch that adjustment unless you are changing the refrigerant type or someone else messed with it and now it is out of adjustment. Kind of like the mixture adjustment. Both are generally best left alone.
David Teitelbaum

[Ratrace427]

I agree with that. As long as you have 2.5 pounds of freon whether it be r-12 or 134 i dont see why the switch would be giving you trouble. Its good to know that it can be adjusted though. Just another awesome design by Delorean. Did you get the clutch fixed? I had this same problem on another car. My clutch coil failed and the few seconds of slipping ruined the clutch surface. I went to the salvage and bought just the coil and replaced it but the clutch would not hold till i hand sanded both surfaces with i think 600 grit. I would think this would be a problem for you as well. Probably a good idea to sand the surfaces just a lil anyways to clean them up.

[DMC5180]

2.5 pounds of 134a is too much.
It should be more like 2.0 pounds.