Looking for a relay for the rear electric grid defogger on a 72 cutlass supreme. Should be a 3 prong, I believe the part # is 1-403561. Thanks.

 

Does your car have A/C? If so there are two relays for the defogger.
Post a picture of the one you need if you can. I think you can use an A/C blower relay and just not use one prong. This relay is common and easy to find.

 

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This is what i pulled off, not sure if its bad exactly but sure doesn't look good. Anyway to test it?

 

Is this for the defog on glass or forced air?

Yes you can test the relay. Might be all it needs cosmetically on the outside is to be lightly sandblasted.

 

Allan,
'72 should be grid on the glass. '70 was last year for blower type, maybe a few early '71s?

 

Yes, this is for the grid type defogger. It hasn't been working so i am trying to figure out what the problem is. Indicator light comes on in the car but nothing else.

 

No, blower types were still available in 72 also.

Is your car AC? Check the engine compartment for the fuse holder bulb. It may be burnt out. Also check the grid wires at the back of the car to see if you have continuity in the grid lines.

 

Do you have a 12V test light? If so, you can diagnose this circuit/relay. I'd have to look at a wiring diagram for your car but if I had to take a guess, I would think the terminal on the far right will get power when you activate the rear defogger switch inside the car. The other 2 terminals should have one that is powered when the ignition switch is in the run position and the other one will have power the same time the far right one is powered assuming the relay works and power flows through the relay. The metal case is the ground so you need to ground the case to fully test the relay. But for now, don't worry about the relay itself. Can you see which wires get power based on the info above and identify the terminals they connect to on the relay? Obviously by checking the wires when they are not connected to the relay you will only be able to get 2 to show power.

Brian

 

I do have a test light. So your telling me to test the wires going into the relay? I should be able to do that, I just need a spare moment. I will let you know how it goes.

 

Yes, start with the ignition off and check the wires to see if there is any power on any of the wires. I don't believe there should be. Turn the ignition to the run position and see if any wire(s) become powered. With the key still in the run position, activate the rear defogger switch and see if any more wires become powered. Explain what you find and where those wires go on the relay. If the wires become powered in a logical order, then we can move on to finding out of the relay is functioning and if it can be made to function if it is not.

 

The defogger, when wired correctly, will only turn on when the engine is running.
It can draw around 17A, so it is something you do not want on with the engine stopped.
The A/C blower relay could be used but the 2-contact connector would need to be modified. A new connector and relay are available at rockauto. This would be a last resort of course if you do not find the exact relay you need.
Your relay could be opened up and possibly repaired.

The switch and relay coil (lone pin on relay) are powered off the voltage regulator through a 3A fuse. With the light coming on, I think this part is good.
The relay contacts close and high current from the junction block flows through a 30A fuse, through the relay contacts (2 close pins) and to the rear grid.
This is how it works on heater only cars. Those with A/C are wired differently to prevent the high speed blower from being used with the defogger on.
Check all the connection on the grid side for burned contacts.

 

I'm trying to offer a step by step approach to help the OP determine what the problem is. Is it the relay and if so, can the relay can be made operable again? Before he starts throwing parts at it or checking a lot of different things, I think it would be good to know if the wires to the relay have power when they are supposed to and if not, then help determine why not. One step at a time. We also need to keep in mind that not everyone who looks for help will have the same skills and knowledge of the systems in the car as others. So aside from a little trouble shooting, this will let him understand how that defogger functions. The system has not been operable and the relay is now removed so the electric grid will not function while these first test steps are done.

Rob, what power feed to the relay will only function when the engine runs? The single wire that powers the relay coil? If so, he needs to know so he can test the wires correctly.

 

I am in the library to use the computer -- I know I have 1 last N.O.S.
Rear Defogger RELAY, that someone else was just asking about , I told
them to call me, like I am about to tell you -- and I never heard from
them.
Call me -- I'll look up yours and see if that's the one I have -- give me
the DELCO # if you have it -- and we can cross it for comfirmation....

Call me -- Craig -- 516 - 485 - 1935.... New York....

 

You are from Wilke Barre, Pa. ------------
Tomorrow night, I'm leaving for the Auto Mania show at Ag Hall
in Allentown, Pa. ----- Thursday through Sunday......1/16 - 1/19....
You can come and pick it up, if you want....

Call me!!!!!!!!!!!!!