1968 Series 1.5 FHC. Twin rad fans.
After a 3 months lay up the fans do not come on when hot. Fuse ok.
Thought might be Otter Switch. Took the two leads off the switch and connected together. Fans did not come on. So not the otter switch?
Could hear clicking sound from the relay attached to the frame just behind the fans as I connected and disconnected the two otter switch wires. Fans still not coming on.
Any expert know what the problem is?
Fans did work about 3 months ago.
Does it look like the relay is faulty?
Many thanks,
John
Cooling fans not working
#1 Cooling fans not working
Last edited by Johnlowe on Sun May 31, 2026 2:33 pm, edited 1 time in total.
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#2 Re: Cooling fans not working
A few other suggestions:
1) Check your battery is operating at a decent voltage.
2) Check that no oxidation has built up on the connections either side of the fuse.
3) Next, with the otter switch "closed" via bridging it, try tapping the side of relay with the plastic end of a screwdriver in case anything is stuck inside preventing the switch to operate.
4) Using a multimeter, see if you're getting current to the fan with the otter switch still in the closed position. If not, then try replacing the relay.
1) Check your battery is operating at a decent voltage.
2) Check that no oxidation has built up on the connections either side of the fuse.
3) Next, with the otter switch "closed" via bridging it, try tapping the side of relay with the plastic end of a screwdriver in case anything is stuck inside preventing the switch to operate.
4) Using a multimeter, see if you're getting current to the fan with the otter switch still in the closed position. If not, then try replacing the relay.
Phil
1964 S1 3.8 OTS
1964 S1 3.8 OTS
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#3 Re: Cooling fans not working
Dear John,
so far you have tested and confirmed that the circuit from the battery to the relay winding works, that the wiring from the other side of the relay winding to the Otter switch is good and that the wiring on the the other side of the Otter switch back to the battery via the chassis is also good.
You can only know whether either or both of your fans are good by applying 12v and earth to them.
You can only deduce anything useful about the Otter switch when you get it up to temperature. If it is good, you should hear the relay click when the temperature passes through its on and off limits.
The circuit diagram for your car will tell you which contacts should make/break when the relay winding is activated and which colour wires carry 12v and the return path to the battery.. You'll need a meter or a test light or at least some spare wiring to be sure.
Since it is unlikely for two fans to become faulty at the same time, the most likely faults are either dirty relay contacts (internal or external) or a faulty Otter switch. If not that, then I'd look at the integrity of the wiring.
kind regards
Marek
so far you have tested and confirmed that the circuit from the battery to the relay winding works, that the wiring from the other side of the relay winding to the Otter switch is good and that the wiring on the the other side of the Otter switch back to the battery via the chassis is also good.
You can only know whether either or both of your fans are good by applying 12v and earth to them.
You can only deduce anything useful about the Otter switch when you get it up to temperature. If it is good, you should hear the relay click when the temperature passes through its on and off limits.
The circuit diagram for your car will tell you which contacts should make/break when the relay winding is activated and which colour wires carry 12v and the return path to the battery.. You'll need a meter or a test light or at least some spare wiring to be sure.
Since it is unlikely for two fans to become faulty at the same time, the most likely faults are either dirty relay contacts (internal or external) or a faulty Otter switch. If not that, then I'd look at the integrity of the wiring.
kind regards
Marek
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#4 Re: Cooling fans not working
Thank you both for your very explicit and helpful replies. I will follow your advice and report back.
Again, many thanks, John
Again, many thanks, John
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