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how can you tell if a relay is bad

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Old 12-04-2010, 06:54 PM
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how can you tell if a relay is bad

i tried to hook up a toggle switch to the relay wire to control pass fan but when i ground it theres a clicking and the fan doesnt work.the fan motor is good.i have it hooked up to the green/white wire at the relay closest to the passngr side.is the relay bad or am i doing something wrong.im planning on getting a aftermarket fan switch so id like to know if the relay works.thanks

Last edited by wastelander88; 12-04-2010 at 10:31 PM.
Old 12-07-2010, 05:02 PM
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Re: how can you tell if a relay is bad

Your fan relay is on the driver side I believe, on firewall next to brake booster - there are several there, one is fan, one is fuel pump. The pass side relay is for the heater blower motor.
Old 12-07-2010, 05:27 PM
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Re: how can you tell if a relay is bad

Actually, I believe your fan relays are both in the front, close to the radiator. Assuming your car has dual fans, the right fan relay is on the right side and visa versa. The clicking and no fan function does sound like a bad relay. To test you can use a test light and look for power at the fan while activating the relay. If no power at the fan, verify power to the relay. If you have power to the relay and nothing coming from it when activated, its no good. On both relays, org is power in, blk/red or blk/pnk is power out.
Old 12-07-2010, 07:49 PM
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Re: how can you tell if a relay is bad

ya ive heard about relays by the radiator but i cant find any there.the only thing thats close by is a red and a orange wire that comes off the fan wires and ends with a plug that has a 20a fuse thats mounted right next to the battery on the fender.fuse in it is good though.the only relays i can find are the 3 next to the brake booster and one for the heater fan but i guess il have to play around with the three relays and try to track down the problem.i put in a new coolant temp sensor and the guy i got the car from said it has a hypertech fan switch.i looked at the switch and its got a new plug spliced in to the factory wire so im guessing it is a aftermarket switch.i dont see how that could be bad already but anythings possible
Old 12-21-2010, 07:17 PM
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Re: how can you tell if a relay is bad

I appologize for misleading you. Both relays are by the battery. One is between the battery and the radiator, mounted on the engine side of the radiator support. The other is hidden behind the battery, about 8" from the first one.
Old 12-21-2010, 08:20 PM
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Re: how can you tell if a relay is bad

On my 91 and 92 the fan relay is one of the three relays by the brake booster. It is the one that doesn't have a green wire, and the one closest to the center of the car. I believe all three relays are the same so you can swap the relays around to troubleshoot, but you might want to label them first.
Old 12-21-2010, 09:27 PM
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Re: how can you tell if a relay is bad

ok... i just did this on my car to fix my relay problem.... here's a good tid bit of info to know... if you have three relays up on the firewall by the window washer pump the two with the gray connectors are for your fans (given you have dual fans like mine) if you want to check to see if the relay is good while its still in the car run a loose wire from a ground and wrap it around a paperclip thats completely straight... with the key in the on position stick your ready made ground into the "f" terminal where the wire connects to the bottom of the relay... for the cooling fan it should be green/white and the ac fan gray.... this will engage the relay and turn on the fan... you may have to wiggle the paper clip around to hear the relay "click" ... worked like a charm for me.. the other way to test the relay is outside the car with a 12v source running to "d" and "f" then check "a" and "e" for continuity...

this may help

http://img331.imageshack.us/img331/6...roscan20nb.jpg
Old 12-23-2010, 03:02 PM
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Re: how can you tell if a relay is bad

Wow! Time to wake up doc. Ive been thinking of my 87 IROC. 91 is way different. Go with DrewsCam. Hes got the right answer on this one.
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