coolant temperature switch

[93spoolin]

ok so I read in an older post about when the coolant temp sensor went out that they just grounded the 2 wires to the thermostat.has anyone else done this..can you do it to the ct switch


also the reason i was asking about this is because I went to napa and autozone and took the switch and they looked them up and told me that wasnt what it was.im confused.my car is at my buddys shop so i cant go look at where it came out.they said it looked like the fan switch. i looked up pictures of the fan switch and I dont think they look alike. is there anyway yall can describe the coolant temperature switch,sensor and the fan switch.or just post pics,i hate parts stores

 

[4g63eagle]

Well to help you understand this better, I'll explain how the fans are supposed to work. There are two seperate circuits. The first has power coming from the ignition switch when you turn the key on, it goes through the coil on the relay, down to the thermo sensor and to ground. The second has power coming from the battery, through the switch on the relay and then the fan motor and to ground. When the engine is cold, the thermo switch is open, and therefore there is no current flow, therefore the relay is not activated, and hence the fans don't come on. When the rad reaches 185 F, the thermo switch is supposed to complete the circuit, grounding the igniton wire, and then the fans will come on.

Hoping you understood that mess, I will explain my idea. If you run a switch after the relay on the circuit that comes from ignition, you can manually complete, or break, that circuit. You will be bypassing the thermo switch and the switch inside the car will take its place.

Now, the terminals on the relay are as follows.

#1 is the farthest to the front and the passenger side of the vehicle. This terminal is the "output" of the switch on the relay and this wire goes to the fan motor.
#2 is the farthest to the interior and the passenger side of the vehicle. This is the "output" of the coil part of the relay (ignition circuit). This wire normally runs to the thermo swich but this is the wire you will run to your switch.
#3 is the closest to the engine and the front of the car. This has power coming from the battery for the fan motor.
#4 is the closest to the engine and the interior of the car. This comes from the igniton.
#3&1 are on the same circuit and #4&2 are on the same circuit.

To summerize this mess. Take the wire at relay terminal #2, run it to a switch, and then to ground. Hope this helps and sorry if its confusing, its hard to explain over the internet.

man i thank you so much for that it was more then enough help thank you i bought my dsm kinda like a barn find this guy had it under a tree with a tarp on it for a long time it had no spark he says it needs a coil pack but it really needed love and lots of it a new ecu went eprom had burned ic 105 "isc" so i threw a new isc in and a ecu upgraded brakes new wheels tires plugs c.o.p setup fab. a new wheel well piece about 15x6 inches etc etc got all that done and have been dealing with no rad fans for about 3 weeks now due to a long shipping wait first a thermostat it didnt even have one in the housing then a rad thermo switch"jumped it at the connection fans turn right on" new relay"jump it there turns right on" new coolant sensor , gauge sensor"the 1 wire sensor" and still no cooling fan action but now so again i thank you very much for that blueprint of your idea i am gonna buy some new wire and i will let you know how it works for me a.s.a.p

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well i went out and i grounded the number 2 pin with a switch and nothing happened so i was wondering if maybe you would have any idea why that wouldnt of worked for me i made a quick drawing of the pass. side relay with the pins i think i have numbered right

 

[1990AWD]

man i thank you so much for that it was more then enough help thank you i bought my dsm kinda like a barn find this guy had it under a tree with a tarp on it for a long time it had no spark he says it needs a coil pack but it really needed love and lots of it a new ecu went eprom had burned ic 105 "isc" so i threw a new isc in and a ecu upgraded brakes new wheels tires plugs c.o.p setup fab. a new wheel well piece about 15x6 inches etc etc got all that done and have been dealing with no rad fans for about 3 weeks now due to a long shipping wait first a thermostat it didnt even have one in the housing then a rad thermo switch"jumped it at the connection fans turn right on" new relay"jump it there turns right on" new coolant sensor , gauge sensor"the 1 wire sensor" and still no cooling fan action but now so again i thank you very much for that blueprint of your idea i am gonna buy some new wire and i will let you know how it works for me a.s.a.p

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well i went out and i grounded the number 2 pin with a switch and nothing happened so i was wondering if maybe you would have any idea why that wouldnt of worked for me i made a quick drawing of the pass. side relay with the pins i think i have numbered right

well from the look of your pic, using the rectangle you have, the tranny side would be where you wrote "engine" and and the engine would be to the right of that. the bottom of the rectangle would also be the front of the engine. then your diagram of the relay would be correct in relation to the car.

If the fan still does not come on when you turn the ignition wire, the relay has probably already burned up. I went through three relays and a fuse before I got it right.

on a side note, I also found my car deserted. Back in 2002, the owner had to put a new engine in the car but could never get it to run right, so he parked it. I bought back in January, put a new head on it, thought I had all the kinks out of the car and my brand new head gasket went now I'm waiting for time to put another head and gasket onto the car.

 

[pyv93awd]

Ok, I get the idea but since I'm a major noob when it comes to electrics and all, let me see if I got this straight. So basically, to turn the fan on manually, you have to ground the #2 circuit and the switch is just an on/off to inbetween the #2 circuit and the ground? Correct? If so, where could I ground the wire?

 

[1990AWD]

Ok, I get the idea but since I'm a major noob when it comes to electrics and all, let me see if I got this straight. So basically, to turn the fan on manually, you have to ground the #2 circuit and the switch is just an on/off to inbetween the #2 circuit and the ground? Correct? If so, where could I ground the wire?

Yes you've got it. You can ground the switch where ever you want. Just make sure it is a metal to metal contact with the frame of the car, then you get proper conductivity.

 

[pyv93awd]

sweet! Thanks man. I'll try this when I get home from school late. Hope it works for me. It's getting cold here so I dont want my fans running all the time, it'll take to long to warm up.

 

[pyv93awd]

I ran into the same problem as 4g63eagle. I connected the #2 to a switch, then from the switch to a ground. I got nothing also. The fans dont turn on and the relay isnt burnt up. I replaced it with the other relay and the relay works still. What am I missing? My car overheated again today and I dont wan to drive it if it's just going to keep over heating and eventually might cause the head gasket to blow. What other ideas are there for hooking the fans up to a switch?

 

[1990AWD]

I ran into the same problem as 4g63eagle. I connected the #2 to a switch, then from the switch to a ground. I got nothing also. The fans dont turn on and the relay isnt burnt up. I replaced it with the other relay and the relay works still. What am I missing? My car overheated again today and I dont wan to drive it if it's just going to keep over heating and eventually might cause the head gasket to blow. What other ideas are there for hooking the fans up to a switch?

You tried a switch on terminal #2 of the relay and it still didn't work? WTF

 

[pyv93awd]

You tried a switch on terminal #2 of the relay and it still didn't work? WTF

Yeah. I had a wire running from terminal #2 (lower left terminal of relay, if you're facing the relay from the passenger side tire) to one end of the switch, then the ground wire to the other end of the switch. Had a ground from within the engine bay. Flipped the switch on and I got nothing, replaced that fan relay with the headlight relay, and headlights worked fine, so relay is still ok but fan still not coming on. Would it be a bad idea if I used the same ground as my battery? I was going to try that because the battery ground is forsure a good ground if my battery is working, right?

 

[1990AWD]

Yeah. I had a wire running from terminal #2 (lower left terminal of relay, if you're facing the relay from the passenger side tire) to one end of the switch, then the ground wire to the other end of the switch. Had a ground from within the engine bay. Flipped the switch on and I got nothing, replaced that fan relay with the headlight relay, and headlights worked fine, so relay is still ok but fan still not coming on. Would it be a bad idea if I used the same ground as my battery? I was going to try that because the battery ground is forsure a good ground if my battery is working, right?

hmmm... I don't see why that wouldn't work. WTF It should in theory. It'll be a while before I'm anywhere close to getting my car ready enough to try it myself.

 

[pyv93awd]

Hmm..wonder if grounding another of the pins will work. I'll try what I can.