1979 Blower Motor Relay

[wbdeford]

If the blower doesn't work at all, what are the odds it is something other than the relay at fault?  The controller seems to otherwise work.

[Dan LeBlanc]

These cars are notorious for killing the blower relay and melting the connector at the fusebox.  If you still have the relay in the factory position, pull it out.  If it's showing signs of melting there, you'll need to get a new relay and pigtail and wire it in.

["Cadillac Kid" Greg Surfas 15364]

William,
You have the motor itself, wiring and the fuse to check. Run a 12 volt line directly to the motor lead first to check the motor and then the fuse.
Greg Surfas

[wbdeford]

Thanks, guys....was wondering if I could just be lazy and throw the part at it and have, say, a 95% chance of it being fixed. 

[gkhashem]

These cars are notorious for killing the blower relay and melting the connector at the fusebox.  If you still have the relay in the factory position, pull it out.  If it's showing signs of melting there, you'll need to get a new relay and pigtail and wire it in.

Dan is absolutely correct. GM issued a Technical Bulletin on these.

My 26,000 mile car blower relay got hot started to melt the relay box. I did as he suggested. Check the relay and the box is it starting to melt or get real hot?

You wire a new relay and a base right into the original wiring and remove the original relay.

https://www.rockauto.com/en/moreinfo.php?pk=818069&cc=1025468&jsn=409

Some info

https://www.cadillacforums.com/threads/1978-deville-blower-relay-keeps-blowing-out-every-3-months.201273/

[wbdeford]

Thanks for the great info!  Since this is such a common problem, I will order a relay....hopefully will get a chance to look at it this weekend.  Hoping to take the car on a weekend trip 11/15.  It heats OK without the blower....eventually....but it takes a long time to be warm.

[wbdeford]

Was too curious to wait....OK, I think this is it, and it indeed looks like something melted and someone removed it.  Also, it looks like a red wire was clipped on the right:

EDIT: Looks like the clipped wire relates to EFI, which my car does not have.

[gkhashem]

Order the upgraded kit, not the original relay since it will just melt or start a fire again.

My base is black in the 1978. But basically you wire in the pigtail/plug and bypass the plate and plug relay into the new pigtail w/plug. No idea about the red wire.

Kit

https://www.partsgeek.com/gbproducts/HC/2806-05039659.html?utm_source=google&utm_medium=ff&utm_content=HC&utm_campaign=PartsGeek+Google+Base&utm_term=1977-1984+Cadillac+DeVille+Blower+Motor+Relay+Four+Seasons+77-84+Cadillac+Blower+Motor+Relay+1978+1983&utm_source=google&utm_medium=ff&utm_campaign=PartsGeek+Google+Basecid=6774379819&aid=79287199093&keyword=304562317638%3A%3Apla-304562317638&kid=304562317638&gclid=EAIaIQobChMI9JOZkdPY5QIVSrzACh3-PgYtEAQYBCABEgKBK_D_BwE

original  NO!!!

https://www.caddydaddy.com/1976-1977-1978-1979-1980-1981-1982-1983-1984-cadillac-a-c-high-blower-relay-nos-free-shipping-in-the-usa.html

[wbdeford]

Yep....that's what I did.

I had a 71 Eldo that wouldn't blow.  I never got around to trying to fix it.  I wonder if the issue was common back that far?

[35-709]

Also take note (while you are in there), the 2 blue solderless connectors and the yellow one above and to the left of the red clipped wire are poorly done and should be cut out and redone properly.   

[wbdeford]

Also take note (while you are in there), the 2 blue solderless connectors and the yellow one above and to the left of the red clipped wire are poorly done and should be cut out and redone properly.

Got it....would you know off hand what those go to?

[35-709]

I am sorry, I do not.

[wbdeford]

Got my new relay, but it contains no instructions.  Four Seasons 35747

It has two large orange wires, one of which has a black stripe.  The shop manual shows 10 gauge red and 10 gauge orange.  Which goes to which, or does it not matter? 
It also has 2 smaller wires--one blue and one brown, while the shop manual shows 20 gauge yellow and 20 gauge light blue.  Which goes to which, or does it not matter?

[TJ Hopland]

I don't know that specific kit and a quick search doesn't come up with that number but from a general theory point of view with 4 wires it should work with fat wires to fat wires and small to small.   If there were just 3 it would start to make a difference.   Fat wires are just a switch so in and out doesn't matter.   Small wires are the relay coil which polarity doesn't matter because its an electro magnet attracting steel so it doesn't matter if its a north or south pull, either way the contact closes. 

[wbdeford]

I don't know that specific kit and a quick search doesn't come up with that number but from a general theory point of view with 4 wires it should work with fat wires to fat wires and small to small.   If there were just 3 it would start to make a difference.   Fat wires are just a switch so in and out doesn't matter.   Small wires are the relay coil which polarity doesn't matter because its an electro magnet attracting steel so it doesn't matter if its a north or south pull, either way the contact closes.

That's what I was thinking about the fat wires....just connectivity....but didn't know how the polarity would affect the operation of the relay with the small wires.  Thanks!

[wbdeford]

Now that I know what it looks like, I can see that this has been replaced before, with a very similar Bosch part.  Ther eis a sticky black substance in there, ans also at the back of the connector....from overheating, I presume?

If I understand it correctly, there should be continuity between the two side terminals, and if I supply 12 volts, I should hear the relay "click".  Correct?

[wbdeford]

OK....now I feel REALLY stupid....When i saw that the old relay was not merely fried, but missing, it should have clued me in that maybe someone fixed it before....both relays work.  So, I tested the motor and got nothing....bad ground at the motor....I moved the ground wire connector to a different screw hole and now it works.

Great lesson I have been too dense to learn.....laziness leads to doing more work.

But question....why does the blower need a separate ground wire when it is screwed to the vehicle body?

[TJ Hopland]

Isn't the box the blower is screwed to fiberglass? 

Those bosch style relays usually have a diagram on the side and use a somewhat standard labeling.  85 and 86 is the coil.  30 and 87 are the contacts.   If its got a 87a that is the less commonly used normally closed contact. 

The black goo I have seen many times and I assume possibly started out as a clear dielectric grease sort of stuff but over time has absorbed other stuff.  I have seen it in connectors that are otherwise clean in cars that appeared to be very well kept and original.   

[wbdeford]

Isn't the box the blower is screwed to fiberglass? 

Those bosch style relays usually have a diagram on the side and use a somewhat standard labeling.  85 and 86 is the coil.  30 and 87 are the contacts.   If its got a 87a that is the less commonly used normally closed contact. 

The black goo I have seen many times and I assume possibly started out as a clear dielectric grease sort of stuff but over time has absorbed other stuff.  I have seen it in connectors that are otherwise clean in cars that appeared to be very well kept and original.   

If it's fiberglass, that would definitely explain it!    One of those things that it didn't occur to me to check.

The Bosch and Four Seasons relays are very similar.  The connector is a little different, with the Bosch requiring the clip being pried upward to release, while the Four Seasons relay has a tab...but the connector has no means to utliize the tab.....

I see 30, 85, 86, 87, and 87a on the Four Seasons, and I think the same are on the Bosch.  A mechanic friend said they sometimes put the goo in there for a part that might also reside under the hood to withstand contaminants that might get in there.

I reinstalled the Bosch and will send the Four Seasons one back, since this isn't a critical part to have a spare on hand. 

Thanks!