Alright so I got my new head installed and my cherokee started up and is running. Now I need help with the next issue. The electric fan does not turn on even when I switch the A/C on. I checked my ground to the aux fan relay it was good. I placed a fused jumper in the relay position pins 1 and 4 and the fan started running. After that I put the old relay back in and unplugged the temp sensor in the T-Housing and the fan started running.When I plugged the the sensor back in it stoped. I went to buy a new sensor from the dealer but the one they said fits my 1996 Jeep Cherokee does not fit the connector. Instead the sensor for a 1998 Cherokee does. So I had no choice but to take the one for the 1998. I even gave one dealer my vin number and it still called out for the wrong sensor. I had the 1998 style sensor in there before when the fan was working.So to sum this up. I have a 1996 Jeep Cherokee Sport with 4.0l. The electric fan is not working even with the A/C on. I installed a new Temp sensor in T-Housing. The fan only works if I jumper the relay connector or unplug the temp sensor. Does anyone have any idea what could be wrong?

 

is the compressor kicking in on the ac?

 

I am not sure in your year, but in my year, the fan will not come on with the A/C switch, only when the A/C system reaches a certain internal pressure. To simplify, the fan will come on in two cases, it will come on at 217 degrees or when the A/C system pressure reaches a certain internal pressure. Sorry but I can't remember what that pressure is. The reason the fan came on when you pulled the sensor is becase the ECU didn't receive continuity through the sensor circuit, thus simulating as if the sensor was at 217 degrees. When the sensor gets hot, it increseases the amount of resistance throught the circut, at which point the computer knows to turn the fan on when it detects that amount of resistance in that circuit. Plug the sensor back in and run the car up to temperature and see if the fan comes on then, I will just bet you it does.

 

The A/C compressor is not coming on. I let the Jeep running for about 30 min but the fan still never kicked in. I am afraid to drive it at the moment because when I changed the cylinder head it was from a 98 and that head does not have the temp sending unit in the head like on the 96. So I dont have a temp gauge! Could the engine just not be getting hot enough? Do I have to drive it to find out?

 

If your ac compressor isn't kicking on either there is also a 20 amp fuse in the cab that will keep both from turning on. This is besides the fuse in the PDC under the hood for the fan. Might want to check that out as well.

 

The first thing you need to do is get your temp gauge working. Not only is it a matter of "safety" for your motor but you also have no way to confirm what your temp is to varify if anything that switches on from engine temp is working when it should or not. Is it cold where you are at? If so, you could have let the car idle for and hour and it might never reach a temperature to where the fan would come on. Well the fact that you took the sensor out and the fan came on indicates that the circut for the fan to come on as it relates to temperature is intact and there should be nothing to keep that fan from coming on unles the sensor was bad. As far as your fan relates to A/C, it sounds like freegdr is on the right path.

 

I forgot to mention in my last post, I just wanted to verify, when you pull the plug on the temperature sensor, you have the relay plugged in to the PCM right? In other words you are not unplugging the temperature sensor and then jumping the PCM where the relay plugs into are you?

 

I agree with 45shutr! The first thing you need to do if get a temp gauge in it so you don't hurt anything, unless you like replacing the Cyl. head.

Once you do that you could simplify things and install an adjustable fan controler and bypass the factory bs. It allowes you to adjust the fan to come on at the temp you want it to, and it also has a circut for the A/C. I did that on my 90 XJ and it worked great, and I'm getting ready to do the same to my 91.

 

is the ac pressure switch plugged in the fan will never start unless the ac compressor starts jump the ac pressure switch bet it comes on then find out why ac compressor is not coming on ..........................................

 

the fan will only come on for two reasons to cool the freon passing thru the condensor or if the motor gets to warm you need to get a gauge working it is a must have

 

another possability

 

when you unplugged the sensor and the fan came on thats show that its working proper the prob is in the ac system

 

Yeah, When I pulled the connector on the sensor the relay was back in place and the jumper removed. Also the weather hear in Maryland is about 35 degrees daily. So it a tad chilly. Does anyone know what I can do about my temp gauge the new cylinder head I installed does not have a space for the temp sender in the head! I have a 1996 and the head came off a 1998. Can you wire the temp gauge into the ECU or something. The temp sensor in the T-housing is the same as it is in a 98 because the one the dealer called out for my 96 does not fit the connector. I ned sugguestions for a temp gauge solution please!

 

isnt that the coolant temp sensor that goes in the t-stat housing not the temp sender

 

your was here right