[prostcelica]

Ok. I baffled. I have my electric fan wired through a temperature switch. On at 195 of at 185. I just built the motor and when I fired it for the first time the fan didn't come on so I pulled the 2 wires from the switch and jumped them together and it comes on so I figured the switch must be hooped. I replaced the switch with a new one but the fan is still not coming on. I tested both switches and they are both defianlty working. The switch is located in the passanger side cylinder head and the temperature sender is in the other head. Ill run the motor till it reaches about 220 degrees. When the fan doesn't come on I pull the wires of the swith and jump them. The fan comes on and the temp quickly drops to about 190. When I pulled the switch water poured out of the head.

Any thought?

[prostcelica]

I should add that nothing has changed (ie wiring wise) since I installed the new motor. I pulled the old one and put the new one in. I only diconected the wires required to pull the motor and then hooked everything back up to the motor the same way. The fan ( with the temp switch) work great with the old motor.

[sunsetdart]

Not positive on this answer but it may be the computer. The computer answers to all the sensors . One sensor may be on its way out.

[lg1969]

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I hope you are running a 30 amp automotive relay

[Irelands child]

I am 'assuming' that this is a non-computer engine, but if it is - oh well!!

These temp senders are grounded, that is, complete the circuit through the actual fitting itself when they heat up(usually a bimetallic component). If you have used a sealer on the fitting or even any adapters to ensure no leaks, they wont work. When you touch the wires together, you will complete the circuit. Oil pressure senders work electrically in a similar fashion as far as completing a circuit.

[NEW INTERIORS]

Originally Posted by Irelands child

I am 'assuming' that this is a non-computer engine, but if it is - oh well!!

These temp senders are grounded, that is, complete the circuit through the actual fitting itself when they heat up(usually a bimetallic component). If you have used a sealer on the fitting or even any adapters to ensure no leaks, they wont work. When you touch the wires together, you will complete the circuit. Oil pressure senders work electrically in a similar fashion as far as completing a circuit.

Very true.. No sealer on the senders..They will not make the ground they need..

[prostcelica]

Motor is a 70's SBC so no computor. Yes I am running a relay and have it wired like the attached diagram in the previous post. I did have teflon tap on the fitting but I had teflon tape on it before. Ill try it with out the tape but I'm not sure that's it (correct me if I'm wrong please) as when the switch heats up and completes the circuit it allows it to go to ground(doesn't groung to the motor. 2 wires of the switch one goes to ground on the relay the other goes to ground on the frame.

[Irelands child]

Originally Posted by prostcelica

Motor is a 70's SBC so no computor. Yes I am running a relay and have it wired like the attached diagram in the previous post. I did have teflon tap on the fitting but I had teflon tape on it before. Ill try it with out the tape but I'm not sure that's it (correct me if I'm wrong please) as when the switch heats up and completes the circuit it allows it to go to ground(doesn't groung to the motor. 2 wires of the switch one goes to ground on the relay the other goes to ground on the frame.

Usually/normally there is a +12VDC to one side of that switch with the body grounded. The switch heats the element, closes the circuit, allowing the 12VDC to flow to the, in this case, the relay. Think of a home light switch. The black wire is hooked to one terminal while the white continues on to the receptacle. Flip that switch on, you then complet the circuit - exactly what you are doing when you jumper the two wires together as you noted above. The body of the temp switch acts like the white wire in the house switch (forget about the bare wire, that's a 'safety valve' and something that wasn't even present until the late '60/'70s) Tape, thread sealer, etc - wont allow the circuit to work (an insulator)

[lg1969]

You can use thread sealer tape. Just cover a small portion of the thread. The exposed thread will connect to the head or manifold.

[ogre]

i've never used teflon tape on an electrical sensor, teflon is an insulator
use pipe dope it will mush out of the way and ground thru the threads

[crownver]

I know the switch he is using and it has 2 terminals, not 1. 1 terminal is attached to ground, so I don't think the switch itself has to be grounded. There should be power to one side of the switch however.