[jeff_herry]

Hy gentlemen.
I continue to restore my 1978 fleetwood brougham d'elegance, and I need again your help or you ideas to solve a little problem.
This time, I try to fix a problem with the A/C system. The blower is operating only in defrost.
When actionning the control panel from Off to economy, nothing happens
From economy to Low: I can hear the compressor relay operating.
From economy to auto: nothing happens
From auto to high: nothing.
From High to bi-level : nothing
form bi-level to defrost: I can hear the vacuum operating, A relay operates, and the blower instantanly runs in High speed.

I've check the blower fuse on the fuse panel. It is OK.
I've checked the blower wiring form the central plug uder the hood to the blower motor. It is OK
I've found a blower relay, not so far from the fuse panel in the passenger cabin (the one that operate). it is a 5 pins bosch number 25525638.
I've visualy check the termistor near the blower under the hood; It seems to be OK
In the shop manual, This problem is identified as an electrical problem... without any other comment.

Up to you what control should I do to fix it ?
thanks for your help.
See you guys.

 

[jayoldschool]

I have read that the 77-79 has blower motor relay issues, and it is common. One of those guys will be here soon to help.

 

[carnut]

The Hi blower relay tends to melt the connection at the relay or at the plug in behind the controls. Check the orange wire to the relay, make sure it hasn't melted its connection. Then remove the faceplate around the radio and pull the dash controls partially out and check for burnt connections usually at the orange wire. Going to defrost bypasses all the sensors and provides a full 12 volts to the blower motor. Try going to defrost then slowly back to AUTO. Sometimes it will activate the blower assuming the engine is up to temperature. The slide contacts wear over the years in the main control head and in some cases require control head replacement with a better used one.

 

[Bro-Ham]

This sounds like a blower relay issue which is common in 77-79 Cadillacs. The relay is located under the dash above the emergency brake, a factory service manual will show you the exact spot. If the relay hasn't been rewired so it is away from its original position you should probably consider doing that sooner than later otherwise it will continue cooking and causing more problems. I'm not a mechanic but I've dealt with the relay problems for many years - I would think that simply installing a new blower relay should put you back in business.

Rock auto is a great source: www.rockauto.com

Good luck!

 

[jeff_herry]

Hello Jayoldschool, carnut and bro_ham,
and many thanks for your ideas.
I've unplugged the relay that seems to be the blower relay, it is a simple throw relay, with 5 pins. I will check this afternoo all the pins with a tester, a multimeter and a 12V battery.
The plug seems to be in bad condition, with lots of contact grease on it. I will test the orange wire to see if it provides full 12v to the relay.
I have opened the panel control and I should have access to the panel control this afternoon.
following carnut, I've gone slowly from deforst to auto (engine off, and cold). The blower reduce its speed slowly and stops when I reach the Hi position on the control panel. Any other ideas ?
I will keep you in touch.
Thanks Guys.
JeFF

 

[carnut]

I said engine at operating temp, and car running! The fan will not work in auto, key on, car off if not up to engine temperature. The grease (old school dielectric) is there to insulate the plug so as to not overheat. Use dielectric grease when you reassemble every connection you check. Clean the copper contacts on the control with something like a pencil erasure. The fan when in AUTO delays the fan until the engine temp is close to about 150 degrees assuming the interior temperature is cooler than the setting you've dialed in. A 90 degrees setting in AUTO will cause the fan to stay on high and not lower automatically all things working normally. With all the windows closed, dial in about 75 degrees on the wheel then verify the fan speed decreases as that interior temp is attained. That's assuming the A/C system works correctly as well!

 

[jeff_herry]

Ok, thanks carnut.
You're right, I've made my contrlos engine car off. So I will start tomorrow and let the engine warm. I will keep you in touch.
On the other way , I've recovered my courtesy lamp, while checking the fuse panel. That helps so much !!!
See you later, and merry X mas !
Jeff

----------

Ok, thanks carnut.
You're right, I've made my contrlos engine car off. So I will start tomorrow and let the engine warm. I will keep you in touch.
On the other way , I've recovered my courtesy lamp, while checking the fuse panel. That helps so much !!!
See you later, and merry X mas !
Jeff

 

[the APEMAN]

Some good advice. Also the engine block temperature switch can be open. The switch must close to get the blower to work when calling for heat.

It is a single spade terminal plug on the corner of the passenger side cylinder head. You can jump the wire to ground to eliminate the warmup problem.

When these cars were several years old almost every one needed the dash controls taken apart as the plug behind the climate control slider had terminals which ran hot. That would melt the plastic causing the termonal to lose contact with the circuit board. The fix was to solder a pigtail onto the board then sooder and heat shrink the socket end.

 

[jeff_herry]

Hy everybody !

best wishes for 2013.

So I continue to search a solution for my blower problem, and here are the things I've found in the last week of hollidays !

The original blower relay has been separated form the relay center, and replaced by a single throw relay. This is due, i suppose, to a heat or fuse of the original relay. the original relay center shows some traces of plastic fuse on it. The original color of the wires connected to the original relay center seems to be respected. the original relay panel shows black or dark brown wires for the 85/86 plugs.It is the same thing on the new relay. then 2 orange wires for the other plugs, but I cannont see a difference with the original wires.

The new relay is plugged with 4 wires.
plug 30 with a big orange wire.
plug 86 with a black or dark brown small wire
plug 85 with a light blue wire
plug 87A not connected
plug 87 orange big wire with black stripe on the side.

According to the shop manual, the original relay is connected with 4 wires, but the copy I have is bad, and I cannot read the propper color of the original wires. The 77 original shop manual is better, but the 78 indicates some changes in the colors of the blower relay wiring...

So I don't know what to do now to continue and solve my problem. The blower still operates in def position, but in the other position of the A/C panel it doesn't operate, even if the engine is started and hot.

I suppose it would be great to make some test on the actual wiring near the actual relay, but I have no otehr idea... if you have some.
On the other way, I've read the ape man Answer, and I can confirm that the temperature sensor on the block is OK. I've checked it with a multi meter and the ohms are OK with the shop manual indications.

Help !

 

[Bro-Ham]

Have you replaced the blower motor relay yet?

My 1979 deVille has climate control problems usually 2 or 3 times per year, regardless of how much troubleshooting, research, analysis, thought, forum brainstorming postings, talking to every mechanic in town - it always seems to be due to a failed or failing blower relay. I have had an electrical expert tear my car half apart trying to figure the problem out, the simplicity of replacing the blower relay has always solved the problem.

I have no clue what the wires mean, I simply get new relays that look identical to the old one, then plug the wires into the exact same places from old to new, has worked for me every time for my car.

This unique blower relay situation seems to be exclusive to the 1977-79 models, I have not heard of problems with 1976 and older nor 1980 and newer. Good luck.

 

[jeff_herry]

Yes, I have repalced the old relay by a new one, without solving the problem.

What I don't understant is:
The 87a plug is not connected. So that means if I really understand how a relay works, that there is no connection for one position of the coil inside the relay...

On the other way, The actual relay has 5 connections, and regarding the old place in the original relay center and also looking at the shop manual, I can only see 4 connections. Is the actual relay of the wrong type? , and what would happen is I would connect the 87a connection to the wire that is now connected to the 87 plug ?
I'm not a specialist in relays, as you can see...

Thanks for help bro-ham !

 

[Bro-Ham]

The replacement relay should also have four connections, like the original, if you have five on the replacement you probably do not have the correct relay. I would suggest www.rockauto.com and they should have specific four post blower relays.

 

[jeff_herry]

Hello !

I'm glad to say that my blower problem is almost solve.
I've disconnected the wire at the pin N° 87 and connected to the 87A pin. The blower is now operating.
Except the fact that the speed are inverted regarding the control panel between Off and Deffoger !
I mean:
in off, it work at low speed, even with the ignition off.
At economy it works at high speed
At low the compressor is engaged and the blower is at low speed.
At auto, hi and bi-level: the blower is at high speed
At def, it is at high speed.

For the moment I haven't recieved the original relay ordered in rockauto, I've only made a test with a simple relay with 4 pins, and it is the same as described previously in my mail.

So I will let you know what happen with the good relay !!!!

Have a good day, and thanks all for your reply.
Jeff

 

[cooterusn]

New to forum, my first post, recently bought a '78 coupe deville w/less than 20,000 miles on it. Looks drives like a new one; but it too has just developed this same
blower motor/relay problem. First problem was bad bearing in blower motor (growl) Bought new motor, worked fine for a few weeks. Now no blower in any position. Put old blower back in. It got no power either. Found 25 amp fuse blown, thought I was golden, replaced, blower worked for about 2 seconds 'till new fuse blew as well. Located and replaced that infamous blower relay to left of fuse panel. Put in another new fuse. Started car, brief warm up, cut climate control to hi with wheel centered on 80*, fuse blew after two seconds. That's as far as I've gotten. Also, none of the tell tale lights seems to be coming on. (are they supposed to light up when engine starts?) but washer fluid light comes on anytime I cut on wipers??? Sent off for shop manuals, any advice appreciated.

cooterusn

 

[carnut]

Sounds like the blower motor is pulling too many amps. exceeding 25 amps. New blower motor? Did you swap the squirrel cage to the new motor?

 

[pompste]

Had the dreaded blower motor relay problem on my '78 Deville 3 years back.Some members can get by by just replacing 2-3 blower relays a year.
My blower relays were blowing out every 2 weeks,so after collecting much information here on fixes for that I found a thread that had a "permanent" fix.I then printed that info and took it to my trusted mechanic who read that info and installed an "underdash rotary dial blower fan switch" and wired a heavy gauge connection from that thru the firewall to the blower motor underhood with it`s own inline fuse and it`s been working great since! 3 years later still working great and not even 1 blown fuse or relay since.

 

[ferrisworld]

I had problems with mine too, and the folks on here suggested replacing the original with two cubes wired in parallel. In addition to that I put a fuse holder in the 12v lead. At first I only had one cube relay although I had installed the dual relay plug. I started with a 15 amp fuse and worked my way up 5amps every time the fuse blew. When I got to 30 it lasted a month before the fuse finally blew again, so then I got a second relay, stayed at 30 amps with the fuse, and haven't had the fuse blow since. It's been almost 2 years now I think.

 

[cooterusn]

Thanks for the response, yes I put the old cage on the new (VDO) motor worked great for a few weeks.

----------

Yes, put the old cage on the new (VDO) motor.

 

[Fivedog]

Hello, I am having a problem very similar to the one Jeff Henry describes in the above posts. I had a 5 plug relay that I don't think was correct, have switched to a 4 plug relay but can't seem to get it right are all four post relays the same or should I be looking for a different type of four post relay? And could someone give the correct order of which plug the wires go to, Orange black, Orange, Brown, and Light Blue Thx....

 

[the APEMAN]

I had problems with mine too, and the folks on here suggested replacing the original with two cubes wired in parallel. In addition to that I put a fuse holder in the 12v lead. At first I only had one cube relay although I had installed the dual relay plug. I started with a 15 amp fuse and worked my way up 5amps every time the fuse blew. When I got to 30 it lasted a month before the fuse finally blew again, so then I got a second relay, stayed at 30 amps with the fuse, and haven't had the fuse blow since. It's been almost 2 years now I think.

Did that to my 1980 Fleetwood back in 2003. Still working fine.