a/c clutch doesn't engage when hot

When my engine warms up (no temp gauge, but After running for 15 minutes) on my 88, the a/c clutch won't engage. I'm getting 13 volts to the compressor. If I tap the clutch with a stick (very carefully so it doesn't send it flying back in my face), the clutch will engage. It wil also engage if I jump the compressor directly to the battery. Am I getting too much of a voltage drop, or is my compressor a/c clutch going bad? It isn't making any noises. How ifficult is it to just replace the clutch?

Does your AC work and does it blow cold air when the clutch is working? Might be low on Freon and that will keep the clutch from kicking in. If the system is charged then the clutch is probally going bad. Not that hard of a job usally have to have a puller to get the clutch ass. off.

The air blows cold when the clutch is engaged. I read something in the manual I downloaded about adjusting the air gap in the a/c clutch. Any idea how to do that?

There is a writeup over at jeepsunlimited.com about wiring the pre-91 AC clutch so that more voltage gets to it thereby kicking it on.

If you are getting voltage it must be magnic going bad. I would replace clutch assy.

There is a writeup over at jeepsunlimited.com about wiring the pre-91 AC clutch so that more voltage gets to it thereby kicking it on.

I saw that, and amgoing to try that first. It just seems to me that 13V SHOULD be enough. If that doesn't work then I'll replace the clutch. I just wanted to be certain there weren't any other parts or service issues I needed to be aware of before spending the money.

When my engine warms up (no temp gauge, but After running for 15 minutes) on my 88, the a/c clutch won't engage. I'm getting 13 volts to the compressor. If I tap the clutch with a stick (very carefully so it doesn't send it flying back in my face), the clutch will engage. It wil also engage if I jump the compressor directly to the battery. Am I getting too much of a voltage drop, or is my compressor a/c clutch going bad? It isn't making any noises. How ifficult is it to just replace the clutch?

On mine..a 97 4.0L Cherokee...the same was happening so I cleaned the ground screw and the weather pack connector. Of course I verified charge also. It got fixed for about 5 months then I have to clean the connection again. It is working now, I just cleaned it yesterday. I will probably solder the wire together next time.

On yours, you might have a sticking clutch. You can replace the clutch or remove it for inspection if you have the tools. Or you can buy a replacment compressor with a new clutch on it already.

On mine..a 97 4.0L Cherokee...the same was happening so I cleaned the ground screw and the weather pack connector. Of course I verified charge also. It got fixed for about 5 months then I have to clean the connection again. It is working now, I just cleaned it yesterday. I will probably solder the wire together next time.

On yours, you might have a sticking clutch. You can replace the clutch or remove it for inspection if you have the tools. Or you can buy a replacment compressor with a new clutch on it already.

Thanks for the tips, I'll give it a shot. BTW, I don't need to discharge the system when removing the clutch, correct?

Thanks for the tips, I'll give it a shot. BTW, I don't need to discharge the system when removing the clutch, correct?

No...you do not have to discharge for just the clutch. You take off the serpentine belt and I remove the mounting bolts and tilt the compressor up to make it easier. I believe there is a snap ring in there (depends on the model). Special pullers are needed you know. There is an air gap spec too when you "push" it back on.

There is an air gap spec too when you "push" it back on.

Can you tell me more about the air gap? What (or where) is the air gap? Between the clutch and compressor body? Thanks in advance.

Can you tell me more about the air gap? What (or where) is the air gap? Between the clutch and compressor body? Thanks in advance.

You can see this in the manual also. Air gap is between the pulley which spins and the clutch which is on the shaft which spins. It is a press fit, so when you push the clutch plate on you should stop when this spec is reached....I forget what it is ...but some gap is necessary. The tool you use to pull it off also puts it on....I think they have instructions. Use a feeler gage to check it.

Like I said, you might pull it off and clean it, and put it back on and have it work again. The clutch has springs on it. The magnet pulls it together. If there is too much air gap, it might not work as reliabaly.
Otherwise, the problem is probably electrical, which is what I have encoutered on my Jeep. The voltage is important as well as the ground. The Sanden compressor unit is used on many other brands of vehicles also. The weather pack connector on the late models seems to be the problem though. (Right hand side under the compressor...the feed wire...12 volts here when system is on.)

Thanks again for your help. I'll look up the air gap in the manual again. I haven't had any luck finding it, but I haven't read all 1200 pages. I'm going to try the electrical trip this week. I haven't tried pulling the clutch off yet, but I did clean all the dirt off with brake cleaner and then hit it with pb blast to loosen it up. It seems to go a little longer before the clutch stops working, but it still quits. I'll try your cleaning method next.

Thanks again for your help. I'll look up the air gap in the manual again. I haven't had any luck finding it, but I haven't read all 1200 pages. I'm going to try the electrical trip this week. I haven't tried pulling the clutch off yet, but I did clean all the dirt off with brake cleaner and then hit it with pb blast to loosen it up. It seems to go a little longer before the clutch stops working, but it still quits. I'll try your cleaning method next.

Just for you...I just measured one for you.
I got 0.010 in. or .054mm on my feeler gage.
Try the electrical ...Like jumping straight to the battery with 12volts and then drive for about half and hour. I have a 97 and every time it has been the connector. Did you check the pressure with a recharge kit...that has a gage? I bought one with a gage for 40 bucks (R134A).

Just for you...I just measured one for you.
I got 0.010 in. or .054mm on my feeler gage.
Try the electrical ...Like jumping straight to the battery with 12volts and then drive for about half and hour. I have a 97 and every time it has been the connector. Did you check the pressure with a recharge kit...that has a gage? I bought one with a gage for 40 bucks (R134A).

Thanks again for all your tips, I'll try them out before I start buying stuff.