• 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.

Aux fan not working!?!?!

9

96TNXJ

NAXJA Forum User
Location
Kingsport TN
ok so my jeep is running hot but nothing the heater cant fix. Im just tired of cooking inside my jeep :flame:!! The fan works (I hot wired it to check) the relay works and it also has good contact. The temp sensor is brand new and if I hot wire it at the sensor the whole circuit works!! What am I missing?? Is my temp gauge bad?? Im so lost!!
 
I unplug it an the fan turns on about 2 sec later. When plugged back in it turns off in about 2 secs. I cross wired the sensor to the plug in and it worked fine so I guess I have a crossed wire somewhere Im not going to worry about it Im just going to swap the wires to the plug in
 
well I thought about maybe a new sensor being bad so I swapped it and I know its the right year because I have a late model 96 and I have the clip for the 97 sensor (which is great because its way cheaper!!) The sensor I bought was the best one that they carried also
 
ehall said:
If it was a bad sensor the engine would run like shit

I'd take it to a shop and have them hook up a scanner to read the output and then go from there
Click to expand...
I'm not familiar with all the configurations but I know some have more than one temp sensor and that sensor may be only for the fan. You may want to make sure the parts store gave you the right temp sensor. If they gave you the one for a gauge it wouldn't work to turn the fan on. The one you need is basically an on-off switch rather than a temp sending unit.
 
The sensor in the thermostat housing is how the ECU monitors coolant temperature. When the computer sees the coolant temperature reach ~220f it grounds the coil side of the fan relay (it does the same thing when the A/C clutch engages) which causes the fan to come on. There are only so many parts of the process here. The first thing to check IMO is to probe the computer for the temperature that it sees and determine if it's close to accurate or close to what is reported at the gauge and pursue action accordingly.
 
winterbeater said:
If you unplug the temp sensor and the fan starts, it must be a bad temp sensor. Is it a '96 like your name?
Click to expand...

yep sure is

ehall said:
If it was a bad sensor the engine would run like shit

I'd take it to a shop and have them hook up a scanner to read the output and then go from there
Click to expand...

I thought about for now just leaving unplugged but like you said it runs like crap. If I leave it unplugged it throws a code that reads that there is a wiring problem and if the sensor is left plugged in there is no code

jeeperjohn said:
I'm not familiar with all the configurations but I know some have more than one temp sensor and that sensor may be only for the fan. You may want to make sure the parts store gave you the right temp sensor. If they gave you the one for a gauge it wouldn't work to turn the fan on. The one you need is basically an on-off switch rather than a temp sending unit.
Click to expand...

As far as I know mine only has the one in the thermostat housing.

ehall said:
The sensor in the thermostat housing is how the ECU monitors coolant temperature. When the computer sees the coolant temperature reach ~220f it grounds the coil side of the fan relay (it does the same thing when the A/C clutch engages) which causes the fan to come on. There are only so many parts of the process here. The first thing to check IMO is to probe the computer for the temperature that it sees and determine if it's close to accurate or close to what is reported at the gauge and pursue action accordingly.
Click to expand...

Can you explain more about checking the computer. (as in how I would do something like that) My jeep normally runs at 160ish and never gets close to the 220 mark (I dont let it) I also tried to turn the A/C on to get it to run and I got nothing
 
96TNXJ said:
Can you explain more about checking the computer. (as in how I would do something like that) My jeep normally runs at 160ish and never gets close to the 220 mark (I dont let it) I also tried to turn the A/C on to get it to run and I got nothing
Click to expand...

Find a shop with a scanner and ask them to tell you the reported temperature while you look at the gauge and confirm the reading.
 
Suggestion, even when you find/fix the fan problem you should wire in an aux switch, so you can also turn it on when you need it. I do not know about your 96 since it is OBDII, but on the older XJ's the sensor for the gauge is on the driver side rear of engine with a one-wire connector.
 
You must log in or register to reply here.

Similar threads

V
High temp woes
2
Replies
21
Views
414
Vitzaa
V
R
Fan not turning on when hot- fan works!
Replies
2
Views
2K
JMA_2001XJ
J
J
XJ coolant overflow after engine is shut off
2 3
Replies
45
Views
7K
XJI6191
X
T
Temp gauge stuck ?
Replies
6
Views
2K
Tonyt22
T
O
2000 XJ Failed Colorado Emissions high CO
2
Replies
27
Views
2K
Ken M
K
Back
Top