Klaatu55

My 1999 Cherokee Sport 4.0 has two problems, which may or may not be connected.
1. A/C is not blowing cold but cabin blower fan is working
2. Auxiliary electric radiator cooling fan is not operating. The auxiliary fan does not come on with defogger setting. (It hasn’t been hot enough to check for operation from an overheating condition.)
3. A/C doesn’t come on for any A/C setting (motor doesn’t change tempo)

Junction Block Fuses #10 (15amp) and #11 (20A) show continuity.

PDC fuses #5 (40A) and #9 (20A) also show continuity.

Fan Relay swapped with starter relay and starter is working as designed. Fan Relay is good.
2 outlets show 12V.

Manual closing Fan Relay causes fan to run.
Manually closing A/C clutch relay causes clutch to engaged. (Heard click)

I did not leave it on long enough to see if cold air would blow in case the lack of functionality is due to some necessary safety feature from the PCM.

I read 3.4K ohms from the Thermostat Housing Temperature sensor when the engine is cold and .93K ohms. When approaching near operating temperature. Dash temperature gauge is working normally.

I hope I provided enough information without overdoing it.

What I believe. I believe battery and fuses are providing current to relays and loads. I believe all pertinent grounds are intact.

I believe there may be a safety interlock preventing circuits from operating probably controlled by the PCM.

HELP.What should I check next?Thank you.

Klaatu55

Found refrigerant was low. Added some and a/C clutch pulled in and aux fan comes on.

crabmushrooms5

Can I jack this thread? same problem

XJC1

Have you done any troubleshooting

crabmushrooms5

Hooked ac manifold guages up with engine off and got 0psi. Just tried to charge refrigerant and it won't take. Should I have checked pressure with engine on?

crabmushrooms5

Sometimes my desire exceeds my knowledge, just a little frustrated. I think I found a couple good things on the WWW

Harky1949

This was covered in a recent post with some wiring diagrams...
My 96 aux fan comes on as soon as I switch on the AC, regardless of whether the compressor pulls in or not, and that depends on freon pressure.
On newer models like your 99, the aux fan and the compressor come on only if sufficient freon pressure is sensed.

crabmushrooms5

tried again this morning engine on / engine off / ac on / ac off. won't take a charge on / off. aux fan won't cut on ac on / off fully warmed.

Coach

If you are at 0 psi, you probably have a leak somewhere. That'll have to be fixed before you do anything else. Once it's fixed, the system will have to be placed in a vacuum so that you can add refrigerant.

Pelican

I am assuming the '96 compressor doesn't have the service valves but thought I would ask. Have you charged it successfully before?

crabmushrooms5

I have had the old compressor blowing cold before it failed. Then I bought the receiver drier, expansion valve and compressor and had it filled but it was winter. Found out it didn't work and had the dealership do it, because I didn't like the work the other shop did. worked for 2 days then they pointed out an evaporator core leak, which was true. had them do it since I was in a time crunch, and soon to be on again.

said I need a thermistor. they did some other SH**** work and I took the dash apart to find that I didn't need one and they didn't "bypass" it like they said. They did put in a new evap core, I checked, the fins are bent slightly but 95% ok.

Now I have an ac manifold gauge set and want to learn how to diy because I'm tired or being ponged.

I have hi / lo test ports.

system was empty with 0 reading lo/hi with engine off. Now I noticed that my electric fan and compressor doesn't come on. no blown fuses not sure about relays.

Engine on, AC on, Fan hi, put a 5oz pag46 in. then 10oz refrigerant and .25oz dye combo in. Shot up to 80psi lo side. hooked up 12oz can of 134a and it doesn't want to take. Channeling my rage as I type

Looking into refrigerant recovery, vacuum, charge with 4.6oz pag-46. Don't want to take it to another shop, but if I do it will be way, way out of town.

crabmushrooms5

I understand trade secret and socioeconomic divisions in marketing, it's cool.

Coach

after you recover the refrigerant and pump it down into a vacuum you have to wait to ensure it holds the vacuum. If not, there is another leak, if it holds then it should be good to go. I don't know about adding more oil, everytime I've seen it done the oil was added to the compressor when it was installed, then add the correct amount of refrigerant and it should be fixed.

crabmushrooms5

I vacuumed for 25 minutes. I disconnected vacuum pump with both valves closed on both sides at gauge since it started to rain. It held vacuum for like an hour. Went to charge and now I'm here.

Should I start all the way over? recover, vacuum then try to charge again(after finding out what I am missing in the charging procedure)?

I am lost watching repetitive videos and reading repetitive articles.

even tried bringing revs up to 2,000 with can attached to yellow, hi closed and lo open.

Coach

Is the compressor running? Clutch engaged?