Discussion
Further to my other thread about a burning smell(!), I tracked it down to the fan relay, and the fan not working.
I've done some diagnostic stuff today and I am really confused.
Both fan fuses are fine, and the relay, although one leg is a little charred, works fine and in any case has been swapped out for a new one.
There is an override switch fitted - one lead spliced into the wire from the fuse to the relay, and the other earthed to the back of the dim/dip relay. There is 12v across the override switch, and the switch itself works.
As far as I can tell, that means that the relay should be energised when the switch is on.
I have tested the fan which works, and I have tested the wiring from the fusebox to the fan itself. It all points to the relay, but I have swapped it out and the replacement is the same.
I was going to check that there was 12v at the switched contact on the relay when the fan is on but I can't find an easily accessible earth in the fusebox...
The only thing I haven't tested is the otter switch, but as the override switch bypasses it it's irrelevant. Likewise, I haven't checked if the fan kicks in if the engine is hot.
Help!
Thing that concerns me most is melted relay but the fuse is intact...
I've done some diagnostic stuff today and I am really confused.
Both fan fuses are fine, and the relay, although one leg is a little charred, works fine and in any case has been swapped out for a new one.
There is an override switch fitted - one lead spliced into the wire from the fuse to the relay, and the other earthed to the back of the dim/dip relay. There is 12v across the override switch, and the switch itself works.
As far as I can tell, that means that the relay should be energised when the switch is on.
I have tested the fan which works, and I have tested the wiring from the fusebox to the fan itself. It all points to the relay, but I have swapped it out and the replacement is the same.
I was going to check that there was 12v at the switched contact on the relay when the fan is on but I can't find an easily accessible earth in the fusebox...The only thing I haven't tested is the otter switch, but as the override switch bypasses it it's irrelevant. Likewise, I haven't checked if the fan kicks in if the engine is hot.
Help!
Thing that concerns me most is melted relay but the fuse is intact...
NiceCupOfTea said:
OK, tried that but no joy - I think I've tested everything now!
Any more ideas?
Just checking - fan should work on ignition pos 2 (engine run) without disabling immobiliser shouldn't it? Can't remember what Carl said the immobiliser acted on...
Normally the immobiliser isolates the fuel pump and the starter circuit. If the engine is at the temperature the fans should cut in then it should run with the ignition on. Any more ideas?
Just checking - fan should work on ignition pos 2 (engine run) without disabling immobiliser shouldn't it? Can't remember what Carl said the immobiliser acted on...
Do you have a multimeter?
If yes then I suggest shorting the otter switch out with a piece of wire and then trouble shooting the relay socket. Find out what you have on each connection. Pins 85+86 are normally the coil of the relay and therefore should have 12v across them (with the otter switch bypassed and the ignition on). Pin 87 should go to the fan and 30 should be a live feed. Note 87+30 could be swapped over, they work either way. Are you really satisfied the replacement relay is good? It is not unheard of to have a faulty new component. I recently spent ages tracing a fault, only to find the brand new relay I had just bought was duff.
Note:
You may need to identify the relay socket locations from the numbers stamped on the relay.
If all looks to be OK, it is possible you have a high resistance circuit in which case all the voltages would appear to be there but the high resistance prevents current from flowing.
I agree, do not necessarily assume the replacement relay is sound. Do check the relay housing, if it has become hot the connections in the housing may no longer connect with the relay. On my S1 THREE of the relay housings had failed at some time and there are aftermarket auxiliary relay holders wired in instead.
Thanks, some great info there.
Just played around a bit more. I can hear the relay clicking when I flick the override switch when the ignition is on, so I think the coil side of the circuit is OK. I have checked the wiring from the relay to the fan, check the fan itself, and checked the fan's earth and all are OK, so that only leaves the wiring to the relay (fuse is good).
I think the next step is to check for 12v in the fuse box and on both sides of the relay. If that doesn't make things clear I think it's time for an auto electrician....
Just played around a bit more. I can hear the relay clicking when I flick the override switch when the ignition is on, so I think the coil side of the circuit is OK. I have checked the wiring from the relay to the fan, check the fan itself, and checked the fan's earth and all are OK, so that only leaves the wiring to the relay (fuse is good).
I think the next step is to check for 12v in the fuse box and on both sides of the relay. If that doesn't make things clear I think it's time for an auto electrician....
Does your fan spin freely?
Earlier this year my fan failed to operate when the cut-in temp was reached, on investigation I found the fuse blown. Checking rhe fan itself, it was relucttant to spin . I replaced the fuse, the fan started running, but was sticking intermittantly. I suspected that the bearings were past their best.
I fitted a replacement kindly supplied by BarryS1, and all has been well since then.
CAUTION: Do not try to spin the fan with your fingers without first disabling the supply.
Earlier this year my fan failed to operate when the cut-in temp was reached, on investigation I found the fuse blown. Checking rhe fan itself, it was relucttant to spin . I replaced the fuse, the fan started running, but was sticking intermittantly. I suspected that the bearings were past their best.
I fitted a replacement kindly supplied by BarryS1, and all has been well since then.
CAUTION: Do not try to spin the fan with your fingers without first disabling the supply.
Quite the opposite - there is a 20A fuse in there rather than the specified 25A.
Did a bit more fault finding tonight. There is 12V at the switched terminal in the fusebox, but there isn't 12v on the other side when the ignition is on and the override switch is flicked (relay clicks so I know it should be active).
I have now tested both relays independently and both work correctly (continuity across the correct terminals when 12v applied).
All I can think is there is a bad connection between the back and front of the fusebox - confirmed by the melt/burn marks on the relay and the fuseboard at the in switched terminal on the relay (30). Presumably it is OK when no current is being drawn, but when the fan was running it got very hot. Again, odd that the fuse didn't blow, and odd now that there is nothing at all - no smell, nothing getting hot, no smoke, and no attempt for the fan to move.
I tried to pull the lucar connector off terminal 30 out of the back of the fusebox but it wouldn't shift.
The only other thing I have left to try is bridging terminals 30 and 87 to power the fan directly - this will confirm that everything else is fine and that it's a problem with the fusebox at the relay.
I think after that it needs an auto electrician - I'm not confident enough with my soldering/crimping skills sadly
I powered the fan for a couple of seconds from the battery - seemed normal, not sure how I could tell if there's a fault in it...
Did a bit more fault finding tonight. There is 12V at the switched terminal in the fusebox, but there isn't 12v on the other side when the ignition is on and the override switch is flicked (relay clicks so I know it should be active).
I have now tested both relays independently and both work correctly (continuity across the correct terminals when 12v applied).
All I can think is there is a bad connection between the back and front of the fusebox - confirmed by the melt/burn marks on the relay and the fuseboard at the in switched terminal on the relay (30). Presumably it is OK when no current is being drawn, but when the fan was running it got very hot. Again, odd that the fuse didn't blow, and odd now that there is nothing at all - no smell, nothing getting hot, no smoke, and no attempt for the fan to move.
I tried to pull the lucar connector off terminal 30 out of the back of the fusebox but it wouldn't shift.
The only other thing I have left to try is bridging terminals 30 and 87 to power the fan directly - this will confirm that everything else is fine and that it's a problem with the fusebox at the relay.
I think after that it needs an auto electrician - I'm not confident enough with my soldering/crimping skills sadly
I powered the fan for a couple of seconds from the battery - seemed normal, not sure how I could tell if there's a fault in it...
Got to the bottom of it - bridging the relay switching terminals the fan works, and with the ignition on and some judicious tapping the fan works on the override switch, so it is clearly that there is a duff connection at (30) on the relay where the heavy duty cable goes in for the fan.
Next question: Best way to solve? I am thinking cut all the wires to the relay at the fusebox, crimp lucar connectors on and just leave the relay hanging. Any better ideas?
Next question: Best way to solve? I am thinking cut all the wires to the relay at the fusebox, crimp lucar connectors on and just leave the relay hanging. Any better ideas?
Finally got round to fixing this by wiring in a separate flying relay socket, seems to work OK.
Was thinking about some sort of indicator to show there is power to the fan. The obvious thing is to put an led in parallel with the fan (just take a lead from the switched output of the fan relay and earth it via a relay).
Just wanted to check I've not missed anything silly - I'm OK to use low amp cable even though it's connected through the high current fan cable aren't I? As it's I'm parallel not series...
Was thinking about some sort of indicator to show there is power to the fan. The obvious thing is to put an led in parallel with the fan (just take a lead from the switched output of the fan relay and earth it via a relay).
Just wanted to check I've not missed anything silly - I'm OK to use low amp cable even though it's connected through the high current fan cable aren't I? As it's I'm parallel not series...
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