A/C & Heater Blower Motor Problem

[EAM 17806]

GREG, TJ and TIM:  After all this knowledgeable communication you guys gave this topic the problem got solved by putting everything all of you stated together and testing and examining the wiring and vacuum tubes I finally thought if all these things I had followed through that you guys suggested was okay then what could it be?  I decided to take a look at the connection of the wires to the blower motor relay which I had sprayed quite a few times assuming the electronic spray would take care of cleaning off the flux, etc., but it didn't.  So then I pulled off the connection and noticed the electronic spray (a name brand one too) didn't do what it was suppose to do. Then I got my ignition files out and scraped all the wire ends that got connected to the blower motor relay and sprayed them and put electric silicone grease on the ends. After I connected the wires back to the relay and tried all the settings,  "WOW", everything worked perfectly. That goes to show us all how important it is to be certain the wire ends are free of flux, etc. THANKS TO ALL OF YOU GUYS FOR ALL THE EXPERT INFORMATION YOU PROVIDED TO THIS FORUM AND TO ME!   Ev Marabian

[TJ Hopland]

Anyone got the electrical drawing for this?  Im just curious to see how the circuit differs from the 75 and 77 books I have.

[Tim Groves]

Just compare the 75 circuit to the 77 Eldorado circuit and you'll see the differences.  The 76 models (exc. Seville) use the same circuit as the 77-78 Eldorados.  Tim

[TJ Hopland]

Its must just be luck that the relay contacts failed as he was doing other testing. Looking at the 77 drawings the symptoms were not fitting a relay issue.  I thought I was onto something when I saw the 75 had 2 relays for the blower but even there did not exactly fit but it fit but it was closer.  At least he has it working at least for now and if it quits again he will know where to look.  Saw a ton of 78 Devilles with that relay and socket melted.  It seemed like an overly complicated relay.  The one I ended up buying I just converted it to a modern 40 amp relay.  It was easy to slide the unburnt terminals out of the block and they fit the new relay it was just one that had to be replaced partially because it was so melted into the socket.  To bad the 80's are not as easy to trouble shoot working on one now for a friend.  It made a bit more sense when we figured out the modulate the ground to the blower to control it.  Got some new manuals on the way.   

["Cadillac Kid" Greg Surfas 15364]

TJ,
That's why the correct year manual is so important.
Greg

[hotrod095]

I am reviving this thread because I have the same EXACT issue that the thread OP had. I have a 76 eldorado which did not have any AC at all. Fan would only blow in OFF or with the ignition on, engine not running (which is expected.)  I have had programmer issues in the past, and last time I had AC trouble programmer swap seemed to solve all of my issues.. well not this time.

I bought a rebuilt programmer from Cadillac Tim here on the forum. This helped my issue tremendously at first; after I swapped the new programmer out I had all my settings a HIGH blower in the defrost, auto, Hi and Lo. The AC compressor always turned when I put the control into any mode except economy, which is expected. I now have the blower cutting off after about 90 seconds of the car running. Blower runs high for about a minute, then the only setting that works is LO.

I read this thread weeks ago and swapped the blower relay with a new one.. I even went and filed all of the plugs with a metal file, cleaned connections with electric contact cleaner and used grease to ensure a good connection at the relay.. Problem STILL persists.

BTW I am in NYC and it has been pretty hot lately, 86 degrees just today. Just to be sure I checked the sensor on the passenger cylinder head behind the alternator. Connection was good and cleaning the connection did not solve the issue either. Any way there could be a fusible link or something causing my issue? I am totally stumped.. any help from this forum is appreciated. BTW I have not checked the blower relay pigtail with a voltmeter and am about to do so now. What readings should I be getting from this test?

Frank A.

[Scot Minesinger]

I would just ground the wire connected to the switch behind the alternator and be done with it - system will always be on whether the car is warmed up or not.  Then the wiring harnesses on the 75 and 76 Cadillacs were low quality.  I have suffered wires backing out of the plastic connectors.  Check the wiring harness connection at programmer behind glove box, push all of the wires in with needle nose pliers and/or re-crimp connector spades so females grab males better.

[hotrod095]

SOLVED! I bought a relay that was most likely incorrect, and trying to work off of this without testing my old one which was still attached to the plastic box by the firewall. I swapped over my plugs to the old relay and Viola! I have a perfectly functioning blower motor now. Lesson learned here, even though the part may be for my car, I should have double checked this against what is actually called for using the part #. In my case the relay was  probably not the correct resistance and was not  closing contacts properly (or in my case opening after 1-2 min).

Frank A.