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The high position uses the relay under the hood and does not use the resistor bank under the hood.

The lower positions use the resistor bank but do not use the relay.

On the high position, power comes from a separate lead through an in-line fuse. I believe this is an orange wire on the relay. This wire should have 12 volts on it all the time. If it doesn't check the in-line fuse or the fuseholder. The switch inside the car closes the relay and applies 12 volts to the purple wire. Believe this is a blue wire on the relay. It should have 12 volts when you select HI and A/C (or HEAT) and the key is ON.

On the lower positions the relay is not used. You should see 12 volts on one of the leads of the resistor. Purple is the output to the fan.
 

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Discussion Starter · #3 ·
For high: I have voltage through fuse to relay on orange wire. I have nothing from relay on the purple wire. Does that mean relay? If so, anyone have part # so I can visit O'Reilly's?
 

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Not really. The relay needs to close so that power from the orange wire ends up on the purple wire (fan). These are on the relay contacts.
Again think it is the blue wire on the relay that goes to the relay coil. Blue needs power to close the relay. Blue's power comes from the switch to close the relay. Make sense?
Blue have 12 volts?
 

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Discussion Starter · #7 ·
As I mentioned the VOM is old and has needle. Set on 50 VDC, I get deflection of 50 (range goes to 250) so that reads about 10 volts between blue and black, same as all the rest. (I know, I need a new meter. This ones at least 30 years old.)
 

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Well, sounds like the relay coil is open. If you unplug the connector, set the meter on "ohms", guesing is will read open between the terminals for blue and black.
Think the GM number on the relay is 1115881. Might double check that. The 69-72 all use the same relay. The same year Novas also use the same one. Might see if the repop places carry one cheaper. Any good relay will work if you cut off the connector. One source. Later, back to the chores.
http://www.automobilearchives.com/parts_list_page_3.htm
 

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Ok, well the wife will whack me if I don't finish varnishing the door.
Try using a couple of clip leads. Hook battery (+) directly to the relay terminal that the blue wire went to. Hook battery (-) directly to the terminal that the black wire went to. The relay should "click" and close. If not, bad relay.
I'll check back after I get the varnish on one side.
 

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Discussion Starter · #11 ·
Well, back to the drawing board, Clicks and hear lots of activty when I did that. Also part is available at local O'Reilly's for $14.95 (borg warner) but guess I don't need it now. What's next?

As for checking power at the blower itself, the purple wire has less than 1 volt and is connected to the inside terminal. The black wire is connected to the outside terminal. The blower will not run at all with the purple wire disconnected.
 

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Originally posted by BobFmTyler:
Relay replaced, fan works on all but lowest speed now. :D Thanks John (again). I'm guessing low speed is resister or switch. I'll try WD40 first.
Quick and dirty way (not an accurate way) to check the resistor is to first take a look at it. It's next to the relay. Usually "toaster wire" will be burnt open.
 
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