About the a/c shim issue...

[Liquid_force]

I have the characteristic a/c problem. It works at start up, and for a few minutes, but once it cycles off it won't re-engage.

I have found that the usual solution is to remove a shim from the a/c, but it sounds like that is only a temporary solution as people seem to be having further problems a year or two down the road.

Is it not the magnetic coil that is weakening/failing over time?

Why not replace that?

I've looked at fordparts.com

There is a listing for the 3.0 (~$59) and the 3.4 (~$200). Both are associated with a 19d798 number, but the cheap one is yb-401-a, while the SHO version is yb-540. I'm unclear on exactly what these numbers refer to.

I found the yb-401-a version for under $30 from another site. I'm guessing that is not a viable alternative.

Maybe that coil's not the problem anyway.

Thoughts?

 

[Mr Anonymous]

Not sure where you read that taking the shim out is only temporary. If it lasted 10+ years with the original shim in place, it should go another 10 with it removed.

The issue is that the two steel surfaces wear like any other clutch, and over time the gap becomes too large for the coil to overcome. Removing the shim moves the clutch hub closer to the pulley surface and voila!

 

[shodoug]

I have heard people say that they only got a couple of years out of their ac clutch after removing the shim. I have about 2 years on mine now.

I have a wild hunch that this might be happening because after a year or two, the refrigerant gets low, and the compressor cycles off and on a lot, and wears out the remaining clutch material.

I figure that the reason the clutch wears down in the first place might often be due to a low refrigerant level causing the compressor to cycle excessively. Then a year or two after removing the shim ( or washer, whatever you want to call it ), the refrigerant level gets low again, causing excessive cycling and wearing out the remainder of the clutch.

Just a hunch.

In my car, I cannot tell when the clutch is cycling due to low coolant. Then it stops cooling very well, and I check it out. It is obvious that I am low on refrigerant from the compressor cycling. As I add refrigerant, the compressor continues to cycle for quite a while, so I figure that it was cycling for a rather long period of time, before getting so low that it no longer cooled well enough.

If the refrigerant leaks out in cooler months, I don't see how you would know at all.

Doug

 

[SHOZ123]

If the pressure gets too low it won't power the clutch coil at all.

I have a new coil if you are interested. The 3.0L will not fit.

 

[Mr Anonymous]

I have heard people say that they only got a couple of years out of their ac clutch after removing the shim.

Again, I don't know WHERE you're "hearing" this, but it's just plain wrong. If a clutch stops engaging after a shim removal it's due to either just too much steel worn away from the clutch hub and pulley surfaces, or the original factory-installed shim was the thinnest available and thus results in a minimal closure of the gap when removed. Having worked on a countless number of these cars, I can't say I've seen more than 2 or 3 clutch gap issues recur after removing a shim (probably done over 100 shim removals). Even then, a quick grinding of the snout of the clutch hub can help close the gap as long as the clutch faces are OK.

I have a wild hunch that this might be happening because after a year or two, the refrigerant gets low, and the compressor cycles off and on a lot, and wears out the remaining clutch material.

I figure that the reason the clutch wears down in the first place might often be due to a low refrigerant level causing the compressor to cycle excessively. Then a year or two after removing the shim ( or washer, whatever you want to call it ), the refrigerant level gets low again, causing excessive cycling and wearing out the remainder of the clutch.

Just a hunch.

The V8 SHO A/C compressors cycle a lot regardless of refrigerant levels. Unless you're running a tune, the clutch cycles with every lock/unlock of the torque converter. Yeah, a low charge will result in more frequent cycling, but usually once the charge gets low enough the A/C stops pumping cold air and people do something about it or enough refrigerant leaks out that the pressure doesn't get high enough to even engage the clutch.

In my car, I cannot tell when the clutch is cycling due to low coolant. Then it stops cooling very well, and I check it out. It is obvious that I am low on refrigerant from the compressor cycling. As I add refrigerant, the compressor continues to cycle for quite a while, so I figure that it was cycling for a rather long period of time, before getting so low that it no longer cooled well enough.

If the refrigerant leaks out in cooler months, I don't see how you would know at all.

Doug

Did you mean to say you CAN tell when the clutch is cycling due to low refrigerant? It's usually pretty easy to tell. First the sound of the clutch engaging/disengaging frequently is pretty noticeable as it the resultant RPM change, and second it doesn't take much leakage to make the A/C noticeably ineffective.

 

[Liquid_force]

Again, I don't know WHERE you're "hearing" this, but it's just plain wrong.

I found it here in some old threads. Apparently it's the exception, not the rule.

 

[SHOZ123]

My shim issue would rear it's head in the summer if you shut the AC off or tried to turn it on when at engine speeds above idle. If I let the car idle it would pull in and stay working at all engine speeds. If I tried to turn it on while driving down the highway it would not engage until I let the engine slow way down. Removing the shim fixed it.