Help req'd, 4,2 cooling fans not working - suspect ecu?

Help req'd, 4,2 cooling fans not working - suspect ecu?

Author
Discussion

rswheelnut

Original Poster:

244 posts

182 months

Tuesday 18th November 2014
quotequote all
Hi, I'm hoping someone can assist...

Recently the cooling fans on my 1996 4.2 stopped working.
Was driving fine but then when parking i noticed the temp starting to rise above normal so cut the engine immediately.
Garage has tested the car and have advised they believe it to be the ECU.
If remove the temp switch the fans should always run but don't.
Fuses and relay ok. If power up the system the fans come on, so the actual fans and connectors etc must be ok.
Garage took cover off ecu and cant see any obvious dry joints, and there's no dampness or anything on or around the ecu (car is dry stored and not used in rain anyway)

Is it common for fans not to work due to ECU?
Is there someone i can send the ecu to for checking and fixing?

Any help would be much appreciated....

OutlawFlat4

697 posts

146 months

Tuesday 18th November 2014
quotequote all
I had a similar problem last week but turned out to be crappy wiring and connectors, which I replaced and solved the problem.

If wired up properly the fans should always come on when powered up and the temp sensor removed, so might be worth checking the wiring and connectors again?

jamieduff1981

8,022 posts

139 months

Tuesday 18th November 2014
quotequote all
Do you have a good earth and a live voltage on the other pin of the loom when powered up but temp sensor unplugged?

FarmyardPants

4,099 posts

217 months

Wednesday 19th November 2014
quotequote all
Are there relays between the ECU and the fans?

rswheelnut

Original Poster:

244 posts

182 months

Wednesday 19th November 2014
quotequote all
thanks guys.
as theyre only cheap i'm now replacing the coolant temp sensor (with a bosch one) and also the relay - although the relays were swapped over before with no change so thats an unlikely one but doesn;t do any harm to eliminate.
may also replace the fan connectors for good measure.
will see if that makes a difference.

if still suspected as ecu, i guess an alternative may be to add in a new temp sensor somewhere to seperately power the fans. or add a fan switch, but i don't want to remember to turn things on and off

FarmyardPants

4,099 posts

217 months

Wednesday 19th November 2014
quotequote all
Check the relevant pinpoint on the ECU with a multimeter relative to a known good earth - there may be a bad contact somewhere as already stated smile good luck

rswheelnut

Original Poster:

244 posts

182 months

Thursday 20th November 2014
quotequote all
replaced temp sensor and whilst doing so i noticed the connector onto it wasn't in particularly good shape so also replaced that. Now seems ok!
thermostat seems to open about 80-85 degrees
first fan comes on at 90 degrees
second as it approaches 95 degrees and it never seems to go above that even stationary, revving and with things like air con on.

result!

thanks everyone for their input. i'm glad no ecu issue!

jamieduff1981

8,022 posts

139 months

Thursday 20th November 2014
quotequote all
FarmyardPants said:
Are there relays between the ECU and the fans?
Yes there are. IIRC each fan is on a different relay.