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Discussion Starter · #1 · (Edited)
i have had the electric fan hooked up in my chevy now for a few years and it works great except for the fact that it is on all the time. I tried to hook it up so it would only come on when the temp hit around 165- 170. I dont know if i have one of the wires hooked up wrong or what. But basically this is how i have it

there are two wires coming off the fan motor, one is a ground and one goes to the relay. The relay has four wires coming out of it, one that goes to the positive terminal on the battery, one that goes to the sending unit in my intake, the wire that goes to the fan motor, then the fourth wire i have hooked up to a power source in my fuse box.

I am not sure if my problem lies in having that wire going to a power source in my fuse box which is activated when i turn my key thus running my fan all the time. So my question is, is why does it do that and why does the relay just not activate once the sending unit reached 165 degrees?

Thanks

oh yeah this is for my 86 chevy k20, just wanted to say before i get killed for posting it in the chevy section. haha, and i dont know how to transfer it to another section. :)
 

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Well first off make shure that your sending unit is an off/on sort of switch, not a variable resistance sending unit. Second verify that at the set engine temperature it is closing, aka making a path to ground. If this is all true then lets look at your wiring. There should be five terminals coming out of the relay, hopefully numbered also. The wire from your sending unit should run to terminal 85 or 86. Then your constant battery hot wire should connect to the number 30 terminal. Then your keyed positive wire should run to terminal 85/86 (whichever one you didn't use for your sending unit wire). Finally your fan positive wire should hook to the number 87 terminal. Careful as there is an 87a terminal. If you were to hook it there the fan would be on constantly till your engine gets hot, then will shut off! If the fan is grounded all should be good. I'll see if I can get a pic up of a relay just in case yours don't have numbers.
 

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The fan running constantly usually means that the engine is always running above the temp of the sender or you don't have enough fan. I had the same problem in my 78. I threw away the electric pos and went back to a clutch fan and never had an overheat since
 

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Discussion Starter · #4 ·
chevy burnout, thanks for the info, i will check it out. KWTMECH the fan goes on once i turn the key, the fan keeps it wicked cool never get above 200 usually right around 175. The relay came wired when i got it but i will ckeck it out anyways and make sure they didnt make a mistake
 

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Discussion Starter · #5 ·
Well first off make shure that your sending unit is an off/on sort of switch, not a variable resistance sending unit. Second verify that at the set engine temperature it is closing, aka making a path to ground. If this is all true then lets look at your wiring. There should be five terminals coming out of the relay, hopefully numbered also. The wire from your sending unit should run to terminal 85 or 86. Then your constant battery hot wire should connect to the number 30 terminal. Then your keyed positive wire should run to terminal 85/86 (whichever one you didn't use for your sending unit wire). Finally your fan positive wire should hook to the number 87 terminal. Careful as there is an 87a terminal. If you were to hook it there the fan would be on constantly till your engine gets hot, then will shut off! If the fan is grounded all should be good. I'll see if I can get a pic up of a relay just in case yours don't have numbers.
I dont believe that is an on/off sort of switch there is nowhere to turn on or off. How can i verify that at the set engine temp it is closing? Sorry if i sound like an idiot, dont mess to much with the electrical side. Thanks
 

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Their should be a thermostat that came with the fan. if it is cal. for the wrong temp. that could cause your problem. It looks like a metal tube with a wire coming out of it and it has something like a contact inside it that will close when the temp gets to the deg. it is set for and turn the fan on. It is hooked up in series with the input power and the coil of the relay.
 

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Discussion Starter · #7 ·
all i have is the sending unit, like one for a temp guage that i have in my intake with the white wire running from that to the relay.
 
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