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AznDrgn · Guest

On my '79 NA I have what looks like a relay, it is screwed into the front frame rail on the drivers side of the car behind the headlight and next accross from the computer box which is on the fender. It has 4 wires that goto it, 2 come from the temperature sensor that is mounted on the radiator and the other two go into the firewall. What is it and what does it do? it's been unplugged since I've had the car and today I decided to plug it back in (only one wire was unplugged. Once everything was plugged in and the screw that held it in place touched ground it started buzzing/chattering, sounded like a relay that doesn't catch. If anyone has any clue to what this is or what it does please let me know as I am in the process of putting the car on the road in 2 weeks and I would really like everything to work right.

Thanks for the help
Danny

924RACR · Posted: Thu May 09, 2002 3:53 am Post subject:

I betcha it's a relay for the AC system, the low pressure cutout.

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AznDrgn · Guest

I don't think so. LP/HP cutouts are normally in the freon lines, this thing has no connection at all with the freon lines or the AC compressor.

Richard · Guest

I'll take a stab at it. Unless you have more than one temp. sensor switch on you radiator than this would be the cooling fan relay. Now I bet you're saying that your cooling fan works. According to my Haines, page 258 on the far right, current track 23 &24 it shows a relay with 5 wires. One goes to additional fuse board #3, one goes to 12+, one goes to 12- and of the two on common terminal 87, one goes to a resistor and its mate goes to the cooling fan. It is interesting that the temperature switch is on the contact side of the relay and not the coil. Looks like contacts are always closed and temperature switch in series with relay contacts makes the fan. Crazy way to make a relay circuit, but there must be a good German reason. Do you have more than one radiator temperature switch? Good place to start.

AznDrgn · Guest

Nope I only have one temperature switch on the radiator. That guess sounds pretty close to what I came up with. My guess was that it is the relay that controls the fan going on to low speed after you turn the car off.

larso · Guest

The previous owner may have added it on for something, are you sure it is stock?

AznDrgn · Guest

After some testing and a lot of wire tracing it looks like it was added on. What it is supposed to do or what I think it was supposed to do is turn on the radiator fan whenever the AC was turned on. Now since I have no AC it is useless. I think this car got an AC put in after it came out of the factory because on my parts car all of those controls were taken care of in the factory wiring.