Fuse keeps blowing

bfc10

Member
I have recently had problems with the car overheating and coolant bubbling back through the expansion tank.


I have changed my coolant temp sensor and i have 4.98v at the connector and checked the continuity all is ok. The voltage also drops as the coolant warms up.


The fans kick in whilst sat idling, but go out for a run the fans don't kick in after and the 10amp fuse in the drivers footwell (4th one up on the right) is blown, now used about 12 fuses


Any ideas where to look next, electronics are not my strong point :oops: so please be gentle with me ;-)
 

oldaneal

Member
If I remember rightly there are two coolant temp sensors one for the ecu and one for the dashboard, for a guess could be the other sensor ? have you tried with one or the other fan disconnected incase thats the fault ?

Im probably wrong with my suggestions but just trying to throw ideas in
 
If a 10A fuse keeps blowing you need to find out why mate, no good just whacking in new fuses every time. Check the fans, one of them could have a short or be clogged with crap and drawing too much current. Like 'oldaneal' says above, diconnect one fan and see what happens, this will narrow down what fan is faulty, then go from there.
 

j0ff

Member
If a 10A fuse keeps blowing you need to find out why mate, no good just whacking in new fuses every time. Check the fans, one of them could have a short or be clogged with crap and drawing too much current. Like 'oldaneal' says above, diconnect one fan and see what happens, this will narrow down what fan is faulty, then go from there.
Trouble is that he says the fans come on fine if he leaves it idling.

Does anyone know if the fans have different speeds?
Is there something else on the same circuit that's blowing the fuse?
 
Trouble is that he says the fans come on fine if he leaves it idling.

Does anyone know if the fans have different speeds?
Is there something else on the same circuit that's blowing the fuse?
Yer true but I bet if he leaves it idling for longer the fans stop working again eventually. A 10A fuse will sit over 10A for a while until it blows, unless the current is a massive short in which case it blows instantaneous. My point is; if the fan is faulty and it's drawing too much current, the fuse may pass this for a while before it blows....might explain why they work on idle, but once been out driving (time passing) the fuse has then popped.
What we need to know is if once he has been for a drive then left it idling....do the fans kick in then? If they do then all i just said is balls.....lol

I think the fans only have one speed mate, the ECU fires them up at 95C.

If the coolant is boiling over into expansion tank, it will be doing this once the car has stopped moving as no air flow......the fuse for fans has gone, so temp keeps rising. I'm betting it is he fan(s) at fault. If it was cooling system problem (stat, temp sensor, even head gasket pressurising coolant) then why would the fuse keep going?
 
Well i doubt they would require more than 10A but i might be wrong. I thought fans were around 80W so @ 12V thats ~7A. I could be wrong though on fan power, just looked on google and saw a few rad fans at 80W, but these were uprated ones.
If you have a multimeter mate, wire it in series with the fan (On the ammeter seeting through fused output obviously) between fan plug and the fan connector pin. You'll need a bit of wire to join second pins together. Bit of a bodge but you'll soon be able to see what the current draw is. Then do the same on other fan.
 
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bfc10

Member
Thanks for the ideas so far however, i have narrowed it down now i have tried with the fans disconnected one at a time and also with both disconnected and the fuse still blows.

I then realised it was blowing the fuse when ever i was booting it, if i stayed just off boost and cruised around it would not blow (with the fans disconnected or not) but as soon as i put down the accelerator it would blow again.

If i just sit it at idle it will warm up and the fans kick in when required, i did this over 5 times with no problems?

Could it be the alternator?

Any more ideas guys ;-)
 
Very strange..... but the fuse that is going is the fuse for the fans right? I'll have a look at the circuit diagram lunch time and try and help more. If you tell me the exact fuse to be sure that will help me, then I can see what the circuit is like hanging off this and what could possibly be going wrong.
 
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bfc10

Member
Very strange..... but the fuse that is going is the fuse for the fans right? I'll have a look at the circuit diagram lunch time and try and help more. If you tell me the exact fuse to be sure that will help me, then I can see what the circuit is like hanging off this and what could possibly be going wrong.
Cheers mate, it is the 'Engine Control' fuse fourth one up on the right hand side.
 
P

pulsarboby

Guest
try removing the harness to ecu then spray connections with wd40 also check the wiring on back of harness to make sure theres not a short circuit.
plug it all back in and see if that makes a difference
 

JIMMYBACK

Active Member
What else has been added to the car recently?

any work electronic or mechanic?

sounds like something as already been stated there is extra current/draw running on that circuit hence the fuses blowing under Load?

any loose/bare wire you can see shorting out?

Good luck
 

bfc10

Member
any loose/bare wire you can see shorting out?
Well after about 4 hours of trying to find the fault in the fan circuit i eventually found the fault, i put in a 15amp fuse instead of a 10amp fuse and found the wiring to the Lambda sensor smoking so disconnected it and lo and behold the wires were shorting out due to where it had been rubbing on the alternator pulley :doh:

Repaired the wiring, replaced with a 10amp fuse and reconnected everything back up and all is running ok :lol:
 
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