QuestionI HAVE A 1999 JEEP CHEROKEE CLASSIC,NORMALLY THE AIR IS GOOD AND COOL,THE OTHER DAY THE CHECK ENGINE LIGHT CAME ON,AND STAYS ON,ALL FLUIDS ARE FULL,AND ENGINE RUNS GOOD,BUT THE A/C ONLY BLOWS WARM AIR,ANY SUGGESTIONS? THANK YOU.
AnswerLee,
Typically the check engine light is separate from the A/C sstem entirely. It would not indicate something wrong with the A/C.
Now with the A/C blowing warm. Automatically this tells me your compressor clutch is not engaging. Obviously. Now there are several reasons why the clutch would not be engaging. First, have you checked the A/C clutch coil fuse? It is very possible that it may be blown. If you check it and it is good...
The next stop I typically jump to is your low pressure switch. This is in the middle of the electrical system and is usually a good starting point. Locate your low pressure switch. Typically it is located on your accumulator. Your accumulator is a silver canister with 2 hard lines coming from the top of it. It is about the same girth as a soda can but stands a bit taller. On jeeps it is usually on the passenger side of the engine compartment close to the shock tower. It should have a switch mounted to it with an electrical connector. If the switch is not there, trace the lines coming from the accumulator until you find it, it will be mounted directly into a hard portion of your lines. Once you locate your switch, disconnect the harness plug from it. With the switch in the run position (engine on or off) and your A/C on... with a small insulated wire jump the connectors inside your harness plug from the switch. You should hear a "snap" from your compressor as the clutch engages. If you do, that tells me one of two things. You either have a bad low pressure switch (about 15 bucks) or you do not have enough refrigerant in your system to close your low pressure switch. Check your pressure with the engine off. As long as you have more than typically 22 PSIG in your system it is enough to close this switch. If you have enough pressure... replace your switch. If you do not... you have a serious leak in your system that needs to be found and repaired before having the system charged back up. (If you need tips on finding it do a follow up and I will give you a few)
If you did not hear the "snap"...
you are going to need a multimeter to check from here. You should be reading 12 volts on one of the low pressure switch harness plug connectors. If you do, that tells me the problem lies in either your low pressure switch, your high pressure switch, or your compressor clutch. If you do not read 12 volts at the plug, that leads me back towards your control head through your A/C clutch relay, thermostat, fuse, or control head itself.
Do the check across your low pressure switch, if nothing, check it for voltage. Get back with me by doing a follow-up on this question, and let me know what you find. This would be a lengthy answer if I went straight through all of the checks.
Hope I was able to help, and if you need more assistance, do not hesitate to ask in a follow-up. Thanks for your question and good luck.
