My old Blazer died...........

[MoMike]

After 12 years of ownership, my old '89 S-10 Blazer bit the dust. I've replaced it with a '94 Grand Cherokee (good ol' Jeep 4.0 liter V6). I'm liking everything about the Jeep but am having a few problems with the AC. Seems the compressor doesn't want to kick in. Am I looking at a new compressor, or is there a switch or fuse I need to find and check out first?

[Bill Gunn]

I would guess the freon leaked out. Do you have a buddy that knows how to work on one? They charge a fortune at the dealers or at garages.

[MoMike]

First thing I looked at. The coolant is right up to snuff.

[Charlie in TX]

Mike, that Jeep has a 4.0l straight 6. There ain't know V to it. That 4.0 is a tough motor. Expect 250k miles, easy.

Now you AC question. Is the compesser cluch getting 12v?

You say the 'coolant is right up to snuff'. The AC uses refrigerant, the radiator uses coolant. How can you check the refrigerant without the compressor running? Every method I know of involves a pressure reading which requires the compressor to be running.

[MoMike]

Mike, that Jeep has a 4.0l straight 6. There ain't know V to it.

Duh, I knew that! I have no idea why I put that in there. I should have said refridgerant instead of coolant.
The guages read right where they were supposed to with the AC turned on and the engine running. Seems like the cfompressor kicks on for a few revolutions of the pulley and then kicks back off for about 30 seconds. Then back on for a couple revs of the pulley, and back off.

[Rock Chuck]

Could be a bad pressure switch. It prevents the compressor from turning if there isn't enough refrigerant to keep the pressure up. Possibly a bad thermostat that's turning it off before it cools.

[LRImport]

Mike, that Jeep has a 4.0l straight 6. There ain't know V to it.

Duh, I knew that! I have no idea why I put that in there. I should have said refridgerant instead of coolant.
The guages read right where they were supposed to with the AC turned on and the engine running. Seems like the cfompressor kicks on for a few revolutions of the pulley and then kicks back off for about 30 seconds. Then back on for a couple revs of the pulley, and back off.

When you say gauges, if assuming you mean a pressure gauge on the A/C recharging port(s). The symptoms you describe are classic for a low refrigerant(sp) condition. If you don't already own one, you can buy a fairly inexpensive recharging kit at you local "chain" parts store. They should also have refrigerant. If you have a leak, I'd opt for the can that also has oil in it for lubricating the internals of the compressor. Stay away from the brands of refrigerant that have a "stop leak" component. They could plug things up inside your coolant system, causing extensive and expensive replacement costs. If you do have a leak and it requires you to recharge more than once a summer, I'd take it in and get it fixed. If it's a slow leak, you can recharge it for around 15 to 20 bucks by yourself if you own one of those recharging kits I mentioned before.

Good luck and let us know what you find.

[ncboman]

LRI, you post like you know your stuff. :)

How come?

ncboman

[LRImport]

LRI, you post like you know your stuff. :)

How come?

ncboman

I slept in a Holiday Inn once. ;):D

I've done a few A/C fixes, spent too many hours in vehicles with busted A/C because it was too expensive to fix on my income back then.

I also spent several months in High School shop back in the day (when R-14 was readily available and Global Warming was unheard of.....) building a working demo/instructor's aid on a tabletop of an automotive A/C sytem from used auto parts. Fun stuff. :cool:

[Hi Ball]

Now first of all before you going telling people to recharge their system, they should have some knowledge and just how much refrigerant they must put into that system. I watched a guy at Auto Zone do that once upon a time! Yeah, he put 2 of the 12 oz cans of refrigerant into his system, using one of those cheap plastic refrigerant installer tools. The system did NOT cool much at all after that stunt! I told him to bring it by the church as I would be working there on a church van's system. I put my gauges on his vehicle and he had 400 pounds of pressure in his system, way way to much pressure. Go figure!!!

How much leaked out? How much is enough? To much and you got high pressure which is not good at all for the system and it will NOT cool down like it should 40 to 48 degrees below outside existing temperature. The best thing to do, is to take that vehicle to a "certified mechanic" who has experience in working on AC car & truck units.

A good set of gauges will cost you $150 bucks! A vacuum pump is another $140 dollars. A new Dryer is around $65 bucks. If you have a lot of miles on the vehicle, it certainly will need flushing out as well, including the "condenser unit" Yeah, working on AC units is fun fun fun and costly if you don't know what your doing. Best have a black light too and check for leaks in the system. Flush the lines~! NOT the compressor ever ok. If the vehicle has over a 100,000 miles on it, get a rebuilt compressor and new Dryer (accumulator) for starters I would also replace those switches too.