• 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.

No Elec. Fan

98XJSport

98XJSport

Destiny is the rising sun
Location
Western Maine
I have a 98 4.0 that I have been trying to get the electric fan to work. The problem I am seeing is not with the fan, if I ground the wire for the coil ground at the ECM, the fan runs fine. So the fan, wiring, fuse and relay are all good. But the computer isn't triggering the fan that I can tell. Ive tried turning on the AC (which doesn't work, more on that later), unplugging the CTS, and getting the engine over 220 degrees, no fan for anything.

Now my AC doesn't work, Ive also heard rumor that if the system isn't pressurized then no fan. Is there a way to make the AC think it is pressurized? How do the people that remove AC keep thier electric fans working if the system is waiting for an AC signal?

Thanks for any help on this, Im at a dead end right now !!!1
 
Temp sensor is good, or at least the gauge readings are good. Not necessarily accurate, but the gauge is functioning properly...
 
98XJSport said:
Temp sensor is good, or at least the gauge readings are good. Not necessarily accurate, but the gauge is functioning properly...
Click to expand...

The temp sensor on the thermostat housing is for the fan on your model year. The gauge temp sensor is on the back of the head, I think. I may be wrong though. Great now I'm brain farting the senor setup.:passgas:
 
Hallo . I found out, that the E fan is working, without pressure on my a/c system. I swapped in also :looser: a switch on the dash now. Also I like to make a resistor on the CTS for earlier E fan switch. Mine E fan is coming very late.
 
I installed a switch on the dash to run the fan as well, but with the heatsoak on a hot day I get a CEL after parking for a bit then starting it up, as the temp climbs the fan doesn't turn on and triggers said CEL. More annoying then anything else.
 
98XJSport said:
I installed a switch on the dash to run the fan as well, but with the heatsoak on a hot day I get a CEL after parking for a bit then starting it up, as the temp climbs the fan doesn't turn on and triggers said CEL. More annoying then anything else.
Click to expand...

That's also a reason to install hoodvents.:laugh3:
P.S I follow all your discussions about this annoying case.
 
Last edited:
Good reason for vents and a radiator flush, looks like mustard in my overflow bottle :puke:
 
Definatly, Ive only ever used pre-mixed in it to top it off once in a while, but no telling what the PO used...
 
Nobody has any thoughts as to why my heater isn't being turned on by the ECM? Everything else works fine, so I don't really think it's the computer having a problem with that one tiny thing...

:dunno:
 
Not heater, cooling fan :confused1
 
sorry for any redundant question...

but sounds like the problem IS the ECM itself...cause if you tried unplugging the temp sensor while the engine is running, the fan should kick in (after about 3 seconds) and through a CEL code.

Would it be possible for you to switch out the ECM with another XJ of the same year?

The only other suggestion I have...assuming that you haven't already done it, is to check the wiring between the fan relay and ECM (continuity/resistance check)...or maybe try cleaning the ECM connector contacts. The ECM should be next to your airbox...
 
Im going to check on an ECM at the pick and pull tomorrow, provided they don't want to screw me over on it. Ive taken the wire going into the plug at the ECM and grounded it, and the fan turned on. Pulling the CTS gave me a CEL, but no fan. No change in resistance from wire to ground, either. 7-900 Ohms, jumping around. Possible that it could be slightly loose in the plug, but I can hit the female within the plug fine with my probe.

Anyone have a rough idea what an ECM should go for? Could one single output go bad? Can it be fixed?
 
So if it's the ECM, is there a way to fix the output?
 
Sorry, don't have any other suggestions...the logic path could be faulty at any point...output relay/opto iso, circuit trace, logic driver, cpu, etc.

plus, I believe those units are seals and all integrated.

If you ever get a good ECM...you could experiment...open it up...tinker with it...

My only suggestion is to make double sure all wires and connections are good and clean before spending a lot of money on a new ECM...

good luck
 
I had precisely the same problem (new sensor, fan comes on with the AC,etc.) about nine months ago with my '93 4.0. I was committed to a 600 mile round trip over the coming weekend and didn't have time to try to track down a wiring fault and in any event, was not interested in changing out the pcm just for the electric fan. I opted for an adjustable thermostat (I believe a Hayden from O'Reilly for ~$40) with a probe that goes in the radiator fins. Temperature stays rock steady at a hair over 210. A band-aid but an effective one.
 
You must log in or register to reply here.

Similar threads

V
High temp woes
2
Replies
21
Views
413
Vitzaa
V
R
Fan not turning on when hot- fan works!
Replies
2
Views
2K
JMA_2001XJ
J
I
911: AC Panel Replacement, Coolant lines, Questions?
Replies
6
Views
1K
iamacynic37
I
tjmotter
Heater box repair - pics needed
Replies
1
Views
1K
75SV1
7
DustyWagoneer
K Suspension 3 Fan Setup for Sale
Replies
3
Views
452
gomncr
gomncr
Back
Top