Ahnenerbe

This project car keeps getting better and better! When I bought this the fan relay blue wire was spliced into the courtesy lights fuse circuit (and when I replaced blown fuse (Ctsy) both horn and fan came on, and temp switch wire (on pass head) was burned, broken and frayed. SO I re-spliced the blue wire to it's correct cut piece and fan stayed off, put in a new single wire temp switch and connector, and ran the car up to 140f and nothing. Doing a search on the forum I saw the wiring diagram and also I tried to short the temp switch wire to block, nothing happens. I even tried shorting the green wire at the relay (which is wired into temp switch) to a ground and no fan operation. The fan relay looks brand new and when I press in the fan relay trigger fan operates. Where should I go from here as this car is making my blood boil.

ToniJ1960

Im pretty sure that 12volts is on one side of the relay coil, and the temp switch grounds the other end of the relay coil.

Tou could check for 12volts on wire that goes to yourt temp switch. Reading the 12 volts through the relay, since with no current through the coil there shouldnt be any voltage drop across it.

If you get the 12 volts there, and grounding the relay coil doesnt activate the relay it has to be a bad relay.

Or if theres no 12 volts thats the problem.

Ahnenerbe

Thanks toniJ, lets just assume that there is no 12 volts on that wire (it's raining so can't check now), then what would I need to look for? It appears the green wire (that connects to temp switch) goes into the wire harness (does it just go back out into the engine bay to temp switch or is tangled up into the dash somewhere. The wire diagram doesn't show where it goes. Thanks again for the help!!

ccrazor

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Ahnenerbe

I just checked for voltage at the switch wire and there is nothing, I also attempted to check the green wire going into relay and it shows nothing as well. So now I am more lost.

ToniJ1960

Check the fan fuse 3amp and check on both sides of it for 12 volts. Then if y ou have 12 volts there check for 12 volts on the dark blue wire at the relay.

I think that may be why someone had spliced that blue wire over to a new 12 volt source.

Ahnenerbe

That will be my Sun project.

ccrazor

You will not see any voltage on the switch wire or the dark green at the relay unless you are getting 12v from the fuse to the relay on the dark blue wire (it would show through the coil of the relay).. As Toni suggested start by checking for 12v both sides of the fuse and then the blue wire on the relay. To check the switch wire put your meter on ohms and connect one lead to the switch wire and the other to the dark green at the relay, you should get close to 0 ohms..

Ahnenerbe

Does anyone know where/how the blue wire gets its power? Is the fuse box hot and that's what gives power to blue?

ccrazor

As shown on the drawing I posted, the fuse is powered when the switch is in the RUN position and supplies 12v to the blue wire..

Ahnenerbe

Ccraz those wire diagrams are good, but sometimes I need the dummies version. Lol How is the blue wire hot, and why is the relay tied into another hot wire coming right from the battery itself? If I test the fuse and have no volts there, what could be the cause of that? Thanks for tolerating my inexperience.

ToniJ1960

If you dont get 12 volts on either side of the fuse, then the problem is the source 12 volts. But thats getting ahead of ourselves .
Ok the reason theres two `hot` wires to the relay. The Blue wired goes back to ignition switch at some point and that supplies 12 volts to one end of the relay coil. When the other end of the coild gets grounded by the switch through the dark green wire, that completes the circuit placing 12 volts on one side of the coil and ground at the other end. The coil `energizes` or conducts current through it creating a magnetic field. The magnetic field draws the metal Armature closed, like closing a switch. That connects the main current carrying wire (the fusible link side) to the fan motor coil. The other end of the fan motor should be at ground (notice in the testing information later it suggests testing t he ground at the motor.) So when the armature pulls in and closes the switch contacts in the relay it allows current to flow through the fan motor to ground, turning on the fan.

The relay is a way to control a large current with a smaller current, most switches dont handle a lot of current well. Notice the coil side of the relay is connected through a 3 amp fuse. The fan probably uses 10 amps or more. Its current comes through the fusible link connected to the battery.

If you get the 12 volts to one end of the coil and the other end of the coil gets grounded, then your fan should run (assuming the rest of the circuit is ok.) But first things first. Get the relay itself to operate.

ToniJ1960

Just another thought dont let it side track you, but if that dark green wire to the temp switch as really burned, I wonder if someone might have shorted across the relay coil and allowed the temp switch to short the 12 volt side to ground, thats about the only way the wire could get burned. If they took out the current limiting portion of the circuit. The Dark Blue wire might be burned somewhere along the line too. Then, not getting 12 volts there anymore, they hijacked another 12 volt source to supply the relay hot side.

Cliff Harris

See the "HOT IN RUN" on the diagram above the FAN fuse? That means the ignition switch must be ON to get 12 volts on the dark blue wire. You can check the FAN fuse: Put one probe on a ground and probe both sides of the fuse. There should be 12 volts on both sides when the ignition is ON.

Assuming that is there, there should also be 12 volts on the dark green/white wire when the AC switch and the temperature switch are open.

You said you ran the car up to 140°F, but the diagram shows that the temperature switch doesn't close until the coolant is above 238°F.

Did you try turning on the AC? Assuming you have enough freon in the system to close the pressure switch, that should cause the fan to come on.

Ahnenerbe

Well friends, I feel dumb. I went out to test my volts at fuse box and pulled fuse, saw that I had power, looked at the fuse and it was blown!!!! I put a new one in and ran car up to 230f and bam, fan came on and went off at 210f and kept going though the cycle. I replaced this fuse when I first got the car so I must have blown it when I was installing new switch etc. Lesson learned, always double check the simple things before panicking. I really thought I had some crazy in dash wiring issue with this car. Thanks to everyone who gave advice!!!!