Re: [Amc-list] Jeep Cherokee question - electric fan, source / sensor location for power?

[Wrambler242@xxxxxxxxxxx]

Well, that's a sucky thing about it.
The ecu uses the coolant sensor in the T-stat housing and the ecu turns the fan on. This sensor is used to tell the ecu engine temp, A/C engagement and it does the rest.
 Since the fan does not work with either the overheat or A/C I suspect a wiring or fuse issue. The ecu rarely looses a circuit, butit can happen so don't rule it out.

   I'd start with a test light to see if you are getting power where it needs to be on the relay.
Then jump across the fan feed lines of the relay socket.
   IIRC the ecu grounds the relay to energize it. If wiring and relay are good you can work around a faulty ecu since it is only this circuit that seems to be effected.
   You could install a manual or thermostatic aftermarket switch to engage the fan with the A/C and when it gets too warm.
  If you look at the relay socket there will be two spade females that are out of alignment and opposite each other.
These are the ones the typically feed the circuit when the relay is energized. 99% of those relays have the wiring circuit right on the side of them!
--
Mark Price
Morgantown, WV
1969 AMC Rambler, 4.0L, EFI, T-5
2004 Grand Cherokee Laredo, 4.7L, Quadratrc II
" Chronic Pain Hurts"

 -------------- Original message ----------------------
From: Jerry Casper <gremlingts@xxxxxxxxx>
>   The electric fan in my '94 Cherokee Sport won't cut on automatically anymore, 
> hasn't since before last year. It's already starting to show signs of 
> overheating with A/C on, so I would like to fix it before the hot season starts 
> fully. I've tried swapping the plug-in fuse/relay in the underhood fuse box for 
> the fan, no go.  The fan works with voltage jumped to it, so I know it's still 
> good itself. So, where is the sensor located that's supposed to trip the fan on 
> located at? It looks like the wires disappear into the harness, and I can't tell 
> without ripping it apart. In the interim, I may just run a hot-wire to the fan 
> to a switch, to have it running when the Jeep is. 
> 
>  Any help is appreciated from anyone else experienced with this problem. Thanks!
> 
> Jerry Casper
> Gremlingts@xxxxxxxxx
> 
> 
>       
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