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Climate Control Woes

Started by Matt Brown, November 26, 2010, 07:50:04 PM

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Matt Brown

My 1970 Coupe DeVille came equipped with automatic climate control. Unfortunately the A/C compressor seems to be somewhat seized, or at least it has some sort of clutch problem. Whenever I turn on the climate control it starts burning up the belt.

So my solution was to unplug the wire harness which goes to the compressor and (presumably) engages it. Now when I fiddle with the HVAC controls they do nothing. Does anybody know if there is any way to get heat in this car without having a working air conditioning system?

I'll eventually pull the compressor out and rebuild it, but I'm in no hurry to get air conditioning for the next few months, and I'm getting annoyed with having to wear a jacket whenever I drive the thing.

Matt Brown

Sorry, forgot the signature.

-Matt Brown

;D

-Matt Brown


Dave Shepherd

Assume you have checked all the involved fuses to start with?

TJ Hopland

You get nothing with the control lever in any position?   There is a sensor in the corner of the head behind the alternator that keeps the blower from going above low in heat modes until the engine temp reaches 120*.  Its a single wire and can easily get unplugged while working on other things.  WHen the sensor reaches temp it grounds so you can test the circuit by just grounding the wire.  This sensor is not used for DEF so selecting DEF should run the blower on HI no matter what.   I dont have a 70 manual so I cant look at other specifics but I wonder if you are getting engine vacuum to the system?   There were also some years that the relay for the blower had issues melting itself and the socket.   Not sure where its located on yours but I know a guy with a 69 that has had issues with his. 

It does sound like your AC compressor is sized up.   IF you need to you can just replace the belts with a shorter belt that skips the AC.  One seems to be fine without the AC.   If you an find someone with a real book there was even a listing for non AC back then.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

"Cadillac Kid" Greg Surfas 15364

Matt,
If the compressor clutch pulley turns freely with the wires disconnected, you have done all you need to to "work around" what is a locked up compressor.  Typically before they installed the superheat circuit in the compressor clutch control circuit, systems would loose charge and with it the oil to lubricate the compressor.  There was nothing to protect the compressor, so it continued to run without oil until is would burn the bearings and lock up.
The other components (fan, heater, temperature control) will function without the compressor running.
In order to carefully diagnose your system a factory service manual with its wiring and vacuum diagrams is a must.
Check the fuse under the dash, check to see if the blower operates when you put the mode lever in the "defrost" position.
Check to see that the blower motor is connected, and while you are at it you can check the motor itself by unplugging the wire to it, running a jumper from the positive terminal of the battery with 12 volts, and seeing if the motor itself runs.
Let us know.
Greg
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

Matt Brown

Heh, finally got my correct username registered.

@Dave: I had not checked the fuses yet. But you're right, that's a good place to start!

@TJ: Doesn't matter what position the lever is in. Even "Fog" and "Ice" do absolutely nothing. I guess the blower motor not running at all is the biggest key to this. Just replaced the belt tonight to bypass the AC compressor, but no change in the system. I do see a little white spark flash behind the lever when it's dark. It happens whenever I go to/from the "Off" position

@Greg: You're right. I was hoping to find a quick fix. Looks like I'll have to start going through things systematically

@Tim: I have a 1967 factory shop manual that I've been using in the mean time. You're right, it is very intimidating to see all of these GM tool part numbers. That troubleshooting guide sounds like just the trick. I'll call you tomorrow to order one!

-Matt Brown

"Cadillac Kid" Greg Surfas 15364

Matt,
Just as a word of encouragement, I have found that 90 percent (I made that percentage up, but let's say nearly all) of the ATC issues are simple, requiring careful checking of wiring and vacuum connections.  Typically simple relays and/or the fan motor or their connections are at fault.  The factory service manuals were intended to instruct automobile mechanics with very little knowledge of air conditioning to diagnose and repair AC systems.  The only specialty controls I can think of for the ATC diagnosis would be the "simulator" and it's primary function is the calibration of the ATC.  The problem/cause/solution matrixes in the manual are invaluable, and I personally have never found them to be incorrect.
careful scrutiny of each component and the interconnecting wiring and vacuum lines takes time.  Buying a bunch of parts and replacing yours can be expensive and frequently  works because in their replacement, you disconnect and reconnect the wires and vacuum lines that had poor connections causing the initial symptoms, cleaning the connections and correcting the problems.
Take your time, learn about the components of your system, and (after you have found and corrected the problem) when something occurs in the future, you will be able to identify and correct the problem quickly.
Greg
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

Jim Sparrow

Unplugging the a/c compressor should have no effect on blower operation. Since 1970 was the last year for GMs "comfortron I" system I believe the blower was started by applying vacuum, through the heater valve to the master switch. Assuming the blower motor will run when 12 volts is applied directly from the battery I would procede as follows. The master switch is usually located on the cowl near the evaporator core. It typically has 4 small vacuum hoses connected to it and one 2-way electric connector. With your ignition on & the climate control set to auto, press up on the bottom of the switch with your index finger. Does the blower start? If so, you most likely have a vacuum problem. If not, check for an in-line fuse (30amp) near the alternator. If you have one, like my '67, that is for high blower speed only. Is it blown? Next, I'd go to the blower relay. This is usually located on the heater box toward the right of the evaporator. You're looking for a small silver box with, usually a 3-way, electric connector. Try tapping it. If the blower still refuses to start, check for power at the relay. Another side note is that when the selector on the dash is placed in "auto-hi" or "defrost" modes the power servo is by-passed. The power servo is the gizmo that controls the blower speeds as well as the air temperature that is being discharged into the passenger compartment. So basicly in those two modes of operation you have a direct hot feed to the blower motor. Hope this helps you out!!    -Jim

JerRita

I had a similar problem when I had a 69 If you need relays etc take out the old part and get the number for some reason the parts catalogs sometimes don't list Cadillac parts but a relay from a Buick or Olds is the same JeRita
Jerry and Rita Trapani #15725 Caddymaniacs

R. Scot Minesinger

Hi,

I have a 1970 Cadillac, and the climate control works great.  When I got it same issue nothing worked.  Anyway all the other replies are right on the money.  The key is getting it working, and then if it stops working fix it immediately because it is likely just one thing broken.  Whereas if you let time go by multiple things fail.  As a general rule if it is rubber original from 1970 it should be replaced (except those under dash actuators seem to all be working well).  

To work on your climate control start with the shop manual, it has a useful trouble shooting section.  Next after making sure that the vacuum hose piping is correct, replace the vacuum hoses in the engine compartment.  There is a comprehensive vacuum diagram that is not in the manual, published in mid 1970 for dealer service.  Send me your address and I can send it to you.

Since the blower fan is so inexpensive ($30 at any parts store), I would replace it if it is original.

It will be well worth it when it is fixed.  The nicest compliment I got on it was when driving with a real particular passenger (not a car person)who drives an expensive new car who is always is messing with the vents and controls on their own climate control-never happy-hates air blowing on them.  We are riding down the road on an 80'F day top up windows up, and I say one of the nicest things about this car is the a/c.  Passenger says well don't turn it on.  I say, why are you comfortable?  Passenger says yes I'm comfortable, don't mess me up.  I say, the a/c has been on for a half hour, it would be very hot and humid if it were not.  Passenger says "wow!"

Good luck, and if there is anything further I can help with let me know.

Thanks,

Scot

bcroe

I once bought a cheap replacement blower motor, made across the Pacific.  After a while I noticed, it didn't put out nearly the air of the old one.  Some more investigation showed it didn't use as much current; in fact is wasn't nearly as powerful as the original.  I went back to originals, many from the junk yard.  Mostly they just need oil on the bearings.  I found various ways to oil them regularly, in some cases drill  hole or add a small copper tube.  Works on my furnace motors too, no more failures with regular oiling.  Those direct drive blowers need the oiling tubes. 

I made a test set which plugs into my 79 Eldo Climate Control.  It lets me set the mode that isn't working, doesn't keep changing while tracing down a problem.  Might be adaptable to a 70.
Bruce Roe

bcroe

The other picture. 

Matt Brown

Thanks for the tips guys! I'll let you know what I find out, and probably post some pics along the way. What with the holidays I've been too busy to tackle this issue since I posted it, however I did get that troubleshooting guide from Tim. Looking forward to having a day where I can go work on this.

Unfortunately it looks like my rear (tailshaft) transmission seal is suddenly leaking, so that might take a higher priority at the moment.