• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

A/C cooling fan...

meengreen

NAXJA Forum User
Location
New Jersey
Where is the thermostat that activates the fan when needed? I want to replace it. Mine never kicks on. The A/C blows nice and cold until the truck gets warmed up, then blows warm. I checked and the r134 is at 34psi. Can't get much better than that.
Then I noticed the cooling fan never kicks on. I replaced the relay for the fan and that wasn't it either. Any other ideas what the problem could be?
 
the fan will come on when the jeep exceeds 210* AND the head pressure on the AC compressor meets a minimum. Odd but true. The sensors that control it are the High side pressure sensor on the AC and the temp sensor in the thermostat housing. The ECU controls actual function when those sensors are tripped and activates the relay.

To test it you actually have to let the jeep get a little hot, probably at idle, in gear, on a sunny day.

If it is never working Have you tested the fan itself by bypassing the relay?
 
Thanks for the great info goodburbon.

goodburbon said:
To test it you actually have to let the jeep get a little hot, probably at idle, in gear, on a sunny day.

If it is never working Have you tested the fan itself by bypassing the relay?

As far as testing, the Jeep got up to operating temp. It was late dusk, maybe it wasn't hot enough? I do remember driving it the next day (wife uses it now) and the fan never came on. The high side tube off of the compresor was very hot. Couldn't even touch it for a second. My buddy says it shouldn't be that hot.
And no, I didn't check the fan itself yet. I did check for voltage at the fan and there was none. That's what made me think the relay or stat that controls on/off was bad. I'll hot wire the fan off the battery tonight and see what happens.
 
BS ALERT BS ALERT

The fan should kick on WHENEVER the AC turns on, and when the car gets to about 215-217.

Hotwire your fan to a battery and see if it works. IF not, replace. Ensure the connector is tight and uncorroded.

If you need a new fan, I posted a thread on here with a cheap, good solution.
 
you don't have to hotwire the fan.

unplug the temp sender on the thermo housing. It should kick on the check engine light and the fan should immediately come on.
 
Jess said:
you don't have to hotwire the fan.

unplug the temp sender on the thermo housing. It should kick on the check engine light and the fan should immediately come on.

Not to sound like to much of a dope, but where the heck is the temp sender and the thermo housing? I want to know what I'm doin', whilst I'm doin' it.:)
 
The tstat housing is where the upper hose and heater hose go into, on the front of the block.

cooling12.jpg


Right dead in the center, except without any hoses attached to it in this pic. The black connector on the right is the temp sender. You can see it is unplugged in this picture. The fan should come on about 3-4 seconds after you unplug it if the engine is on.
 
darjevon said:
BS ALERT BS ALERT

The fan should kick on WHENEVER the AC turns on, and when the car gets to about 215-217.

Hotwire your fan to a battery and see if it works. IF not, replace. Ensure the connector is tight and uncorroded.

If you need a new fan, I posted a thread on here with a cheap, good solution.


Research a bit before you call BS. They changed the way they operate for the late models. I have a 97 and it comes on whenever the AC is on or when the jeep gets over 215. The wife's 2000 will only come on when the head pressure is high enough and/or the engine temperature is high. I thought hers was malfunctioning, brought it to the dealership and they charged me $60 to tell me that this was normal operation. I got the FSM for hers and sure enough if you look at the schematic it is true.
 
goodburbon said:
Research a bit before you call BS. They changed the way they operate for the late models. I have a 97 and it comes on whenever the AC is on or when the jeep gets over 215. The wife's 2000 will only come on when the head pressure is high enough and/or the engine temperature is high. I thought hers was malfunctioning, brought it to the dealership and they charged me $60 to tell me that this was normal operation. I got the FSM for hers and sure enough if you look at the schematic it is true.

Ok, my apologies. Any visual differences to the system?

Here's my electric fan alternative thread:

http://www.naxja.org/forum/showthread.php?t=920264
 
pauldo39 said:
The tstat housing is where the upper hose and heater hose go into, on the front of the block. The black connector on the right is the temp sender. The fan should come on about 3-4 seconds after you unplug it if the engine is on.

I checked right when my wife got the truck home from work. I figured I'd need to check it whil it wasn't working properly. I unplugged the sensor and the fan came on, just like you said it would. I also figured I'd try blocking the heater hoses. I clamped both, thinking that maybe the hose valve is bad and was feedeing hot air that was counter acting the cold. That wasn't it either. Then I checked the freeon charge. It was 120psi!! Then I realized the compresor wasn't kicking on at all. I think I narrowed the problem down to the compressor failing to kick on after it's hot. My question now is, why would it stop kicking on after the truck is hot? You guys have been a big help so far, and I appreciate it very much.
 
which pressure was 120 Psi? High side or low side. Low side should be around 35 when the comp is running. High side should be about 180 IIRC (I could be way off)
 
I just had exactly the same problem (cold air when starting, dies when hot), and found that it was a slipping compressor clutch. It would work for a while and then stop when it heated up. It's a metal to metal clutch, and it gets mighty hot if it slips. Mine finally quit altogether, but for a while it was hard to diagnose, because I'd check it cold and it would appear to be working. It was also deceptive because my aux fan had a cracked blade, and vibrated a good deal, so when the clutch failed it still sounded as if the compressor was working hard. In my case the problem was rust, and I have at least temporarily freed it up, though I think it's a little less than optimal. But at least it's working.

First thing to do is to check if there's voltage going to the clutch. If not, then you may have a relay or other problem in the system. If the clutch relay and the safety switch and all are working and sending voltage to the clutch, you can test further there. With the engine off, if you hot wire the clutch lead to battery positive, you should be able to feel the magnetism at the hub with a screwdriver. If it's magnetized, but not engaging, the clutch is bad. If it's not magnetizing, the coil is probably bad. Both can be replaced without opening up the AC system, but need some special tools.

If the clutch is rusty, you can free it up if you're careful where you hit, but don't bang on the round studs with rubber washers behind them. If you bend the heads down, it will prevent engagement.
 
It was mentioned above; I can't speak for the way the fan behaves other than my 94, BUT; I would suggest getting your a/c recharged correctly. Goodburbon said that the 01 model fan only comes on when the pressure drops too low, and if your pressure is that high it will NEVER come on. I should have asked before, when you said your fan never came on when the jeep got hot, what temp is that?? Mine doesn't come on until the jeep reaches 220+, which takes forever. If your fan isn't coming on even then, I would replace the tstat housing coolant temp sensor (really cheap), and if that doesn't work, the relay.

Getting your pressure readjusted in the a/c may fix your problem. At that pressure there is no way in hell that fan would come on!
 
I would get a cheap multi meter. One with 15 DC volts and 1K Ohms will do. They come in real handy for tracking down problems like this and many others. Even a continently tester (12 volt bulb with leads) would work for many jobs.
 
pauldo39 said:
Getting your pressure readjusted in the a/c may fix your problem. At that pressure there is no way in hell that fan would come on!

I checked the low side. the gauge won't fit on the high side. They make the fittings different to prevent accidently hooking up to the wrong side. It was reading so high because the compressor wasn't pumping. When it's cold and the compressor is actually on, it reads 34psi. I need to know why it's not kicking on now.

Maybe I should start a new thread." A/C cooling fan..." is a little inaccurate now.
 
Back
Top