1979 DeVille Climate Control Issue (was Relay Block Issue)

[0maha]

I've got a problem with no-op on the climate control fan.

Decided to troubleshoot it today, and found this. That's one of the connectors on the high-amp side of the A.T.C. Blower Relay.

The relay itself looks and tests fine.

Any ideas how to proceed?

Can I remove that relay holder without tearing things up? Access is poor, and I can't tell how it is mounted.

I assume replacing the relay holder is not happening, and I'll need to suss out a way to restore what I've got.

Any advice/direction would be most appreciated!

Thanks!

[TJ Hopland]

That was a common problem and its usually the relay getting hot that causes it.   Looking at your photo the actual connector doesn't look discolored so that means the heat wasn't at that connector.    How long have you had the car and how long has the blower not worked?   Maybe someone in the past replaced the relay?

If you want it to look original you have to find a replacement.    If you want it to mostly look original you could remove the connector from the damaged area then cut out the damaged area of the block leaving room to access and or pass the connector through.   You would then either pull the wire and connector through and plug it to the relay then feed the rest back in and plug the relay in or plug the relay in then from the back plug the connector in. 

Or a better fix that should never fail is go get a 'Bosch relay' from any parts store ($5-$20, release the connectors from the block, plug them onto the new relay, secure it and insulate the connections if needed.  If you need part numbers and wire colors just ask I'm sure someone here could help out.   I don't remember if I have a 79 book so I could not be sure about colors.

[0maha]

I've only had the car since last August.

I'm not worried about authenticity on something like this. I just want the climate control to work.

When I first got the car, the climate control worked. Then it went intermittent. Then it went out completely. That's over the course of about 1000 miles.

Any ideas on how to remove that relay block? If I could get to the back side of it I could work something out.

Thanks!

[0maha]

You were right! I was able to find the clip tabs behind the block. Popped it off, and was able to get enough slack on that wire to get it plugged in.

Didn't solve the problem, but needed doing anyway. On to the next thing.

Thanks!

[0maha]

Ok, starting to feel dumb here.

The service manual has five options for a blower no-op condition.

#1 Is a bit of a pain, so I'm doing the easy ones first.

#2 Checks out. I think I have it sorted.

On to #3, but for the life of me I don't know where that 15A fuse is located. The only fuse on the diagram that says anything about AC is a 20A and I already verified that that one is good.

Can anyone direct me to where the "15 amp A/C-heater fuse" is located?

Thanks!

Update: I verified no power going to blower motor. Also verified that if I connect the blower motor directly to a power source it works.

[Cadman-iac]

Well I don't have a 79 service manual,  but I do have a 77 and a 78 supplement manual.  In them it shows a 25 amp fuse just for the blower motor. Have you checked it out? I've attached a picture of the fuse block diagram with a pencil pointing at the suspect fuse.
Other than the compressor fuse, this is the only one I find for the entire system.
I'm beginning to think that they misprinted the fuse size.  I hope this helps.

Rick

PS: This particular drawing is from the 78 supplement manual.  The 77 service manual shows exactly the same thing as yours does,  so that's why I think it is a misprint. Both the 77 and 79 don't even have a fuse size listed in the spot where the fuse is located. As you can see in this second picture from the 77 manual.
I couldn't sleep so I thought I would do something useful and try to help someone else.

[0maha]

Richard, I think you've nailed it!

I poked around last night on YouTube, trying to see if I could find anything. Found this video https://www.youtube.com/watch?v=qS9d2lH916k, and it looks like the exact same problem I've got.

I went back and looked at a photo I took of the fuse panel, and there it is: A melted fuse, just like the guys in the video and in the exact location you described. Looks like the diagram in my service manual does indeed have a misprint.

I haven't gotten this one to the finish line yet, but the stuff from that video seems right on. In their case, the blower motor itself was the root cause. It was smoked, and even though it worked, it was pulling too many amps.

They ended up wiring in a separate fuse holder, since the one on the fuse block was melted beyond hope.

I think this explains everything: The melted connector on the relay, the melted fuse. The only thing I don't get is why that fuse didn't just blow instead of melting. That part doesn't make sense to me.

Elsewhere in my service manual (in several places, actually), they describe that as a 15A fuse. I think I'll start with that and see what happens. With luck, my stock fuse block is still usable at that location. Worst case I'll have to wire in a new fuse holder like the YouTube guys did. But I'm going to start by pulling and inspecting the blower motor.

[Cadman-iac]

Jeff,
I'm glad you found the problem, and the video too. That is very helpful for sure. All I did was locate an error in the service manual. Unfortunately that is more common than most people realize. It also took me a while to even locate the diagram of the fuse box in the 77 manual. It was easier for the 78 supplement.
I don't know how the 79 book is,  but I noticed that the 78 book has huge color schematics for all the models in the rear of the book. I'm talking about pages that are 3 to 4 times the size of the book.
Good luck on your repairs,  I hope that the worst is over and it's no more than the obvious now.
Glad I could be of assistance.

Rick

[0maha]

I'm working off the "Service Information" manual. (Sorry for the tiny pic. It's all I could find.)

I've got the "Electrical and Vacuum Circuit Diagrams" manual on order. Should be here just in time after I get this sorted out! 

I'll be interested to see if that fuse location is correctly identified in the vacuum book.

I find all this stuff to be endlessly fascinating. It is really cool how they got all this sorted out back before computers and digital controls using nothing but vacuum circuits and simple electronics components. As much of a headache as it can be, at least everything is serviceable.

Thanks again for your help!!