AC works, then cuts out when engine gets hot

[zak]

Another day, another SHO malady.

My AC works, and gets pretty cold, but after about 20 minutes, or whenever the engine temp guage gets to mid range, it will cut out. Twice now I have shut the AC off, driven the car at 40 to 60 mph for several minutes, and then gotten it to come back on (compressor turning ). Today after 15 minutes it cut out and would not come back. Seems like the recovery period is getting longer, and the time point to when it quits is getting shorter.

What should I be looking at? CCRM? AC clutch coil? I just did a front 60k, and did not get the AC belt very tight - it chirps quite loudly when the belt is cool, but not once it gets warm. It did chirp a little before, so can not rule out a clutch gap problem.

Any advice appreciated.

 

[shopartsnw]

I recommend you check your A/C clutch gap. It sounds like the same issue I have seen a couple times.

Mike

 

[luigisho]

After clutch gap I would look at replacing the coolant sensor and switch. In my GenIII I thought I had a clutch issue but I had to replace the sensors and that kept the ac engaged normally.

 

[LJRuddy]

I have this same problem on my gen 3. I have also noticed that if I am going WOT for longer than a few seconds or driving above ~4,000 rpm, my ac will cut out and never come back until I do a cold start.

...Its your clutch gap.

 

[jmpSHO]

I have this same problem on my gen 3. I have also noticed that if I am going WOT for longer than a few seconds or driving above ~4,000 rpm, my ac will cut out and never come back until I do a cold start.

...Its your clutch gap.

At WOT or above 7k RPM (not sure of the exact RPM) your A/C is supposed to cut off to protect it.

 

[LJRuddy]

At WOT or above 7k RPM (not sure of the exact RPM) your A/C is supposed to cut off to protect it.

I know this. But it is also supposed to turn back on afterwards. It doesnt do this. :wave:

 

[jmpSHO]

I know this. But it is also supposed to turn back on afterwards. It doesnt do this. :wave:

Then you have a problem sir.

 

[LJRuddy]

I have this same problem on my gen 3. I have also noticed that if I am going WOT for longer than a few seconds or driving above ~4,000 rpm, my ac will cut out and never come back until I do a cold start.

...Its your clutch gap.

At WOT or above 7k RPM (not sure of the exact RPM) your A/C is supposed to cut off to protect it.

Then you have a problem sir.

 

[SHO_ROLLER_2]

Bah, who needs A/C anyway.

A TRUE SHO owner LAUGHS in the face of heat!!!

 

[zak]

Thanks for all the replies. On the AC clutch gap, I had taken out one of the two washers ~ 50 K miles/7 or 8 years ago but had forgotten the exact symptoms. Think I took out the thin one, but it could have been the thick one. Found out this AM that Ford sells a shim select kit for about $21 list.

Interesting that if you get the cars engine temperature too hot it will cut out the AC - sort of what is seen on mine. In diagnosing why it has been running on the hot side, I've found my OEM radiator cap, at 107 K miles and 15 years old, is only holding 12 to 13 pounds pressure vs its rated 16. Just picked up a cap at Ford today, apparently the RS90 has superceded the RS80 our cars came stock with.

For those not aware, aftermarket caps can have wide variability in their rated relief pressure (especially the lever type IIRC), and their springs often fatigue more rapidly than OEM (and therefore not hold appropriate releif pressure). This lower pressure can reduce the boiling point of the coolant substantially.

 

[luigisho]

Yes my sensors were not allowing the low automatic cooling fan to operate properly. The engine temps ran hot and the ac would not operate until engine temps dropped substantially. I thought it was clutch gap until I replaced the sensors and now all is good (with that issue at least).