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Radiator fans no go

Greg D

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Hi All

The other day sitting in rush hour traffic the temp rose close to 100 deg which it hasn't done before so I switched on the air con to get the fans to start, but nothing happened. Traffic flowed ok so it never got too much over 100 but normally the fans kick in and the temp drops down when sitting for longish periods in traffic. Not being that good with electronics I have only tried the following. I removed the fans relay and tried one of the other relays next to it and the fans kicked into life straight away, obviously a slightly different type of relay as the keys were out of the ignition! I purchased a new relay but this has not helped at all. It doesn't look like the air con is switching on either. Before I jump in the car and drive down to the auto electricians are there any suggestions for fault finding this one? The car is a 1988 carb Turbo. Thanks.

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Just guessing cause I don't know the 88 carb turbo at all.

But the other relay you tried was able to jump the electricity to turn on the fans, cause it was not the correct SPST relay IIRC. I'm guessing you used the nearby headlight relay which is DPDT (or DPST).

The correct relay doesn't work, so I think that the problem is in the sensor that tells the fans to kick on...?? Guessing it is the otter switch? But I don't know the 88 systems at all...


Vulcan Grey 89SE


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How old is the thermostat. I had the opposite problem in that the water temp was very low and it turned out to be the thermostat sticking open. Perhaps your is not opening and the temp guage is reading high but the otter switch is not telling the fans to come on.

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I had the same problem with my 88 carb turbo and it turned out to be the otter switch on the water down pipe. If you short out the terminals on the otter switch the fans should start. If they do then theres a good chance its the switch. If you remove the switch and place it in boiling water you can check it with a multimeter. They are not complicated but you will need new gasket sealer and the ability to wire lock it back in place so that the system doesn't leak when re-assembled.

Cheers Chris

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Yep it will be the otter switch mine was doing it, the connections are pants. give them a good clean up with some emery cloth and terminal cleaner.

Should be ok then


Amateurs built the Ark

Professionals built the Titanic

"I haven't ridden in cars pulled by cows before" "Bullocks, Mr.Belcher" "No, I haven't, honestly"

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Thanks everyone for your help, I have got the Otter switch working by cleaning the terminals with emery cloth and contact cleaner (Thanks Chris) it cuts in when the temp gauge reads about 100, seems a bit high but they turn on and the temp drops quite quickly. Seems like I have dodgy connection or there is something wrong with the air con unit as sometimes when you turn on the air con it does not start (nor do the fans), all you can hear is a clicking under the dash when the control knob gets to about 3/4 around its travel, when it does decide to work there is a loud click from the engine bay and the idle adjusts to take up the additional load. A dodgy air con motor?

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Are they gas dependant then?

Mine is completely empty and the compressor clunks on and off with the dial up front every time.

Need to gass it to see if it works.

There's only 1 wire to the air con compressor and it's connected via a bullet connector.

Maybe it's a dodgy connection or broken wire that works intermittently when the car bounces around?

Edited by Simon350S

Chunky Lover

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There should be a low pressure switch on the reciever/dryer that stops the compressor clutch clicking in if the gas is low.

Too many Toys are never enough !

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