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79 DeVille Phaeton, 57 Eldo Biarritz, 79 Fleetwood d'Eleganc
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139 Posts
Discussion Starter #1
Hi All, As the title says, I have a new to me and nearly new (21K original miles) Fleetwood. I have already done a search and swapped out the seemingly problematic blower relay and I still have the heat on at all times. It has the ACC unit and the car is in immaculate condition all the other features work but when I move the AAC lever to anything but off it blows hot air in the cabin. Even when turned off it still blows hot from the bottom vents. Does the system just need to be recharged?
Thanks for your help
Cheers Robert
 

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1980 FBC
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980 Posts
Diagnostics for this are beyond the scope of my keyboard.

The shop manual has it and will pay for itself in 5 minutes.

You can open the dash and look for vacuum lines trouble but it could be something completely different. The heater core air bypass door A.K.A. air mix door comes to mind.

Replacing a blower relay will sooner or later leave you needing another one because it does not address the root cause of the problem. You may have found that in your search.

Not sure how much air you are getting with the system turned off but it never really turns completely off. Low blower is constant.

Best of luck, enjoy the car : )
 

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1990 Brougham, 1990 Brougham d'elgance 1979 Coupe
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1,196 Posts
Sounds like a real nice car.

A easy check would be to see if the compressor comes on and the big lines are getting cold.








d the large
 

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79 DeVille Phaeton, 57 Eldo Biarritz, 79 Fleetwood d'Eleganc
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139 Posts
Discussion Starter #4
The compressor rotates with the belt but does not come on, the car is really pristine inside all the door rubbers are like new so I don't think it's the vacuum lines cracking. And yes Apeman it never turns off the Low blower is constant (and hot). I have a shop Manual in my 79 Phaeton so I guess I'll have to get over to the worlds slowest body shop and dig it out of the trunk.
There are two almost twins to my Fleetwood for sale here now on Craigslist
an 80 with 135K kilometers asking $2,800.00 and an 81 with 21K original kilometers for $6,500.00
All the same color it would be great if I had a bigger garage!
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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6,737 Posts
Pull the glove box liner out. Now you can see a metal threaded rod on the top of a black plastic box. With the car running, rotate the temperature wheel to max cold. Leave it alone for a couple of minutes, then rotate it to max heat. Leave it alone for a couple of minutes. You should see that box move the threaded rod to blend door closed, then AT MAX HEAT YOU SHOULD SEE THE ROD MOVE TO MAX HEAT. If it doesn't move at all or very little you have a stepper motor failure within that black box. Also verify the ribbed hose from that box is in place both at the black box and the in car temp sensor behind the Cadillac script on the dashboard. If that hose is falling apart or its off, it wont signal the black box to alter the direction or temperature of the CCU. Also by the receiver dryer is a 2 pronged plug for the low Freon pressure sender. You can unplug that with the car running and jumper across the plug with a paper clip. If all the electrical systems work, that jumper should cause the compressor clutch to kick in. If that happens, you're too low on Freon. In order for the AUTO climate control system to maintain a steady cabin temperature, it blends hot air from the heater core with refrigerated air from the evaporator. The relay you replaced ONLY controls dash fan speeds.
 

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79 DeVille Phaeton, 57 Eldo Biarritz, 79 Fleetwood d'Eleganc
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Discussion Starter #8
Pull the glove box liner out. Now you can see a metal threaded rod on the top of a black plastic box. With the car running, rotate the temperature wheel to max cold. Leave it alone for a couple of minutes, then rotate it to max heat. Leave it alone for a couple of minutes. You should see that box move the threaded rod to blend door closed, then AT MAX HEAT YOU SHOULD SEE THE ROD MOVE TO MAX HEAT. If it doesn't move at all or very little you have a stepper motor failure within that black box. Also verify the ribbed hose from that box is in place both at the black box and the in car temp sensor behind the Cadillac script on the dashboard. If that hose is falling apart or its off, it wont signal the black box to alter the direction or temperature of the CCU. Also by the receiver dryer is a 2 pronged plug for the low Freon pressure sender. You can unplug that with the car running and jumper across the plug with a paper clip. If all the electrical systems work, that jumper should cause the compressor clutch to kick in. If that happens, you're too low on Freon. In order for the AUTO climate control system to maintain a steady cabin temperature, it blends hot air from the heater core with refrigerated air from the evaporator. The relay you replaced ONLY controls dash fan speeds.
Thanks for the detailed reply, I will try to get at it this weekend when I have some time. I am sure that the blower relay I replaced was fine, but when I searched here it said it was the most common problem and it was an easy swap to make sure. I have acquired some Freon r-12 and the tap so when it arrives I will have the coolant to recharge the system if needed.
Here are the links to the twins......
http://vancouver.craigslist.ca/van/ctd/5023423833.html
http://vancouver.craigslist.ca/bnc/cto/5007948166.html
 

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1983 FWB (Mac), 1981 SDV (Junkyard Dog)
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734 Posts
Rob..........How could you not go after that grey 81 sedan?? It is right around the corner from you and it looks gorgeous. I am going to check it out on Friday.

Cheers........R.
 

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79 DeVille Phaeton, 57 Eldo Biarritz, 79 Fleetwood d'Eleganc
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Discussion Starter #10
Didn't come on the market till after I bought the 79 in Victoria, however I really prefer to have the 425 under the hood, plus all the extra parts I have for the Phaeton come in handy. I am daily driving the Fleetwood and it's getting warm outside as you know so I will have to deal with the ACC sooner rather than later.
 

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1980 FBC
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980 Posts
Here's a picture of what the older air mix box (A.K.A. controller) looks like:

http://www.ebay.ie/itm/77-1978-79-Cadillac-Deville-Brougham-AC-Heat-Climate-Programmer-Air-/191553986962?hash=item2c9981e192

The later ones used to strip the motor gears and make a clicking sound. Definitely different. I do not remember the older ones being a problem except for the vacuum lines getting pulled off enough to cause a leak.

I don't even know if the '77 thru '80 ones use an electric motor of if they were just vacuum. My car has one and it still plays fine.
 

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79 DeVille Phaeton, 57 Eldo Biarritz, 79 Fleetwood d'Eleganc
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Discussion Starter #14
I had some time this weekend so I cleaned the plug on the AC condenser and got it running but the lines are hot and do not cool off.
I have come r12 cans I am thinking the next step is to add it. Is the low side port on the line to the condenser or on the back of the canister on the firewall?
 

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79 DeVille Phaeton, 57 Eldo Biarritz, 79 Fleetwood d'Eleganc
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139 Posts
Discussion Starter #15
Well the AC problem is solved, it was the sensor on the firewall on top of the AC box under the hood. Unfortunately the shop had to convert it to R134 as it is illegal to use R12 here. However it does work perfectly now and gets nice and cool. I have worked out almost all the bugs (antenna, small trim missing etc.) but it is having a little issue with slow acceleration now. I had the carb rebuilt and a tune up, but the almost stall in an intersection when you are creeping forward is a bit annoying.
 

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95 Concours / 88 Broughm D'el / 76 Coupe D'el
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115 Posts
Well the AC problem is solved, it was the sensor on the firewall on top of the AC box under the hood. Unfortunately the shop had to convert it to R134 as it is illegal to use R12 here. However it does work perfectly now and gets nice and cool. I have worked out almost all the bugs (antenna, small trim missing etc.) but it is having a little issue with slow acceleration now. I had the carb rebuilt and a tune up, but the almost stall in an intersection when you are creeping forward is a bit annoying.
Talking with a mechanic friend of mine, he told me that the ERG vavle sticks and causes a vacuum leak at low speed on those 79's, such as hesitation pulling off from a red light. You may want to look into that. To my understanding the EGR valve can be disconnected and the hose to it sealed and it will eliminate the problem... though you may get small engine knocks from time to time. Or have the valve, rebuilt, replaced, or something.
 
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