: AC Problems

06-27-11, 07:23 AM
Hi everybody. I just joined and this is my first post. There seems to be a wealth of info here and hoping someone can help me out with this, and hopefully I'll be able to repay the favor when someone else has a problem.

So I pay money to some service for an answer and get no reply. Here's what I wrote:

Hi, My name is Larry and I just purchased a 1981 Cadillac Fleetwood Brougham. Upon taking delivery of the car, I immediately noticed the heater core leaking and bypassed the heater core by disconnecting hoses to the the vacuum control valve and bought a barbed fitting to connect the two hoses together for the ride home. Had the core replaced and everything hooked back up. Don't know if this temporary disconnect caused the problem I'm about to describe. The climate control is behaving very irregular. Set the temp to 65 on auto and cold air blows hard and won't stop blowing cold air. When I switch to low or high on the climate control panel, warm air starts and is followed by full blown hot air. It seems like the climate control doesn't know what to do. Not sure if there is an interior ambient temperature sender that has failed or what else to check for before condemning the whole climate control computer.

It occured to me that the heater control diaphram valve with the vacuum actuator may be stuck in the always open position last night. I will check that it is working properly today.

Any help would be most appreciated. Thanks, Larry

Yesterday, 6/26, I discovered that the vacuum line that is attached to the heater control valve created vacuum when the climate control is in AC mode ONLY on High and Auto. As soon as I switched to low, the vacuum stopped. Is this normal? Does the heater control diaphram valve close on vacuum and remain open until vacuum is applied? I'm tempted to put a ball valve inline to shut the flow off to the heater core and see what happens. I still get the impression that hot air is being mixed with cold air, even when on Auto or High, as the air really isn't "ice cold" after being recharged last week.

Also, after putting my foot into the acccelerator pedal, warmer air comes with AC on Auto or High for a minute or two, then cools back off.

I know this topic has been discussed here before, but can't find it.

Thanks much.

06-27-11, 02:49 PM
Would you have a way to acquire the FSM for this car?

The other thing that comes to mind: When you replaced the heater core... any way you could double check all sensor connections?
Seems like a sensor got caught up where it shouldn't be, and now it's giving a bad reading to the climate control.

Sorry I couldn't be of more help!

06-27-11, 09:19 PM
The heater control valve receives vacuum from a vacuum actuator, controlled by the A/C programer. When the programmer commands MAX A/C, full vacuum is applied to the control valve, blocking coolant flow to the heater core. Because "LO" wouldn't be MAX A/C, the control valve is supplied low vacuum to remain partially open, so some coolant can flow to the heater core. It's possible that the vacuum was too low for you notice.

Being that there is vacuum on the hose and cold air in AUTO, the heater control valve and programer vacuum actuators are operating properly in the HIGH and LO settings. The Programer also controls an air mixture valve that mixes the heat from the heater core and cold air from the A/C evaporator. The Programmer could be shorting out internally, and forcing the mixture valve to allow full heat.

I personally never use the HI or LO settings on my ECC. If you leave it on AUTO, the climate control will automatically variate the in car temperature, until it matches your desired temperature setting.

06-27-11, 10:00 PM
Thanks. I definitely want to get my hands on a service manual, but not sure which one(GM or Chilton, maybe both) or where to get them. I Haven't really looked , so I think I can buy one. I have done some extensive research online and found some very helpful and useful info.

For instance, I came across a site that detailed the use of the onboard computer diagnostics with the ECC panal being the eyes into the system and proceeded to check out any problems. I've only had the car on the road for a few days and noticed that the idle was a bit high. With the gears being as high as they are, and the torque available at the low end of the RPM range, I found myself literally idleing along at close to 20 MPH without touching the gas. I knew that needed attention and the brakes were not liking it much either. I ran the diagnostics and came up with a trouble code 34 which is Vacuum Sensor/MAP Hose (DFI) Open MAP Sensor Circuit. Well it seems someone else had been there before. I found the sensor and on the female side of the connection is an insert that only allows the plug (3 wire) to go together one way. Well, why the insert was in backwards, I don't know, because it's obvious because the locking clip for the connection is bass akwards and couldn't be secured. Anyhow, removed the white insert, rotated it 180 degrees, and the leads matched up correctly as they are lettered. Well the trouble code disappeared, and the idle slowed down to what I would consider normal, guesstimate ~ 600 RPM. No tach, so I really don't know, other than it "feels" right, and the brakes are liking it too. Don't know if this was done intentionally or if it was a mistake, but I'm glad it's corrected.

I didn't replace the heater core itself, but I only observed an inlet and outlet port with no electrical connections visable for any sensors, so I don't think the core was installed improperly. I did learn that there are more individual vacuum hoses on this vehicle than the entire inventory of my local sew and vac store.

There is some sort of threaded rod actuator that is attached to a lever that drives some electronic gizmo, looks like maybe some sort of rheostat, and it seems to be binding. It's got a 3 x 6 inch plastic cover over it with lots of electrical circuity and vacuum hoses that I believe control the various ports/ducts for the air to go through. I figure these hoses do that function because when I first reassembled the box, I got nothing coming out the mid vents. Disassembled the black box and discovered that one of the 3" long hoses was disconnected on one side. Reassembled and the air blew out the vents like they were supposed to.

Anybody know anything about that rod actuated lever? I'm thinking that may be the culprit.

06-27-11, 10:19 PM
I'd go with the factory manual because it is exactly what GM gave to their technicians in the dealership. You can usually find them for reasonable prices on eBay. Here is a list of auctions for factory service manuals (http://shop.ebay.com/Manuals-Literature-/6029/i.html?rt=nc&Make=Cadillac&_nkw=1981%20Cadillac%20Service%20Manual&_catref=1&_dmpt=Motors_Manuals_Literature&_fln=1&_sc=1&_sop=15&_ssov=1&_trksid=p3286.c0.m282). You want the ones that just say "Service Information" on the front; the "Advance Service Information" copy was the bare minimum information that came out between the '80 and '81 model years.

06-27-11, 11:01 PM
Thanks Sven for the link. I'll check it out and save myself some time and money. Real help. Really appreciated. I would never have guessed in a lifetime that the "Advance Service Information" is inferior to the plain old "Service Information" you've suggested. Thanks for the heads up. I'm thinking about the 1500+ page factory authorized version for 48 bucks by Bishko. Sixth from the bottom on the link you provided.

06-27-11, 11:36 PM
That one might have a little extra information, added after the first publication, but it probably wouldn't be any more helpful than the one for $14.99.

06-27-11, 11:49 PM
Done deal. 20.86 bucks, including shipping for the one you suggested. Should recieve within a week or so.

07-03-11, 08:50 AM
OK. So I've got my service manual,($20 well spent), and decided to dig deep behind the glove box and try to figure out what'sn wrong. I noticed that the acuator that controls the air mix was acting weird, so I take it out and lo and behold, the damn gears that drive the programmer for the air mix linkage are stripped. The part # on the sticker is 16005902. I was getting 7 volts to the motor, but it just spins and doesn't have the teeth to turn the rotary shaft to change the air mix. Any suggestions? I've searched online for this part and have come up empty handed.

07-03-11, 09:42 AM
I would get one from a junk yard (from a newer car). Any Cadillac RWD, made from '81-'89 would have that air mix motor; '90-'92 Broughams probably do to, but I don't know for sure.

07-03-11, 10:19 PM
Thanks sven. That info really opens it up quite a bit. Makes the search easier.

My parts guy Bob, at County Auto Supply in Wakefield RI, can make my search even easier. He's always glad to help and I've been going there since I was sixteen years old. Hell, it wouldn't surprise me if he had a brand new one on the shelf. My heater core I replaced came off the shelf. Bob blew the dust off the box, and inside it was a brand new original, 100% shiny copper and dull solder beauty, with not a bit of plastic. 41 bucks. What's better than that?

I've got a 1965 Continental flat head M6 industrial engine with a right angle drive that drives a pump when the power is interupted at work. He usually has everything I need on the shelf for that old engine, and if he doesn't, it's there the next day. So I'll be stopping by with the ride after work on Tuesday. He's looking forward to seeing the car, and I know he'll help. He's actually got a website for his tiny supply house that has everything:
If anyone's interested, click on the picture for an enlarged detail look/see of the building. It really is a blast from the past. Bob, the crew, the clientele, and the place are 100% OSKOOL.

08-22-11, 09:49 PM
Well it's a month and a half + since I discovered the problem with the ECC. Much to my amazement, a 1984 Fleetwood Brougham showed up at a tiny junkyard/repair shop/hole in the wall garage literally a mile and a half from my house. It was there for some kind of insurance appraisal for repair and the car is/was owned by the insurance company with plans for a meeting with the crusher for the 300 bucks/ton scrap value. I begged the guys to offer the insurance company 500 bucks for it and bring it around back where I'd pick at it for I'm sure well over the 500 they might've been able to get it for. No go. If I had a spot to put it, I'd have grabbed it myself.

But the guys were kind enough to pull the programmer that I needed for the ECC. Actually all I was interested in was the moter and gearbox for the rotary driven air mix actuator, but it was easier to pull the whole programmer. 30 bucks. I took the motor and gearbox off the replacement and attached it to my original programmer. Well things were improved, but still not quite right. The air mix door would only operate full open or full close. At 85 degrees, I was still blowing cold air and the door was hard in the AC position.

After referencing my service manual (best money spent in awhile) I discovered an adjustment for the potentiometer and the specs for adjusting it. W pin with one lead and ground the other on a multimeter. Spin th potentiometer adjustment and .2 volts equals one degree.

I was just getting ready to do the multimeter thing and see where I was at, when a retired Cadillac mechanic happened upon the scene. I'm not making this up as the truth is often stranger than fiction. This guy told me that common practice was to spin the screw back and forth, and set it in the center. Well I put my electronic stuff away, did as he suggested by setting the potentiometer in the middle of the range (it was pinned hard over to one extreme when I first checked it), and now the ECC is behaving like factory new. Climate control is a beautiful thing!

I tried to get the opera lights, but the guys at the garage said that it would be blatently obvious if they took them, so I missed out on a couple of jewels. Oh well, I'll be keeping my eyes open for a pair of them.

08-22-11, 11:03 PM
I'm glad everything worked out well for you. It sucks about that car, but it was great that you could get some odds and ends from it before it was destroyed.

I have never see an working pair of opera lamps (in person), so I highly doubt you would find a working pair in a junkyard. There have been a lot of threads about rebuilding them, but nothing has panned out. The best solutions have been rebuilding them with LED's or cheap Electroluminescent Tape (similar to what's there, but not exact).

08-23-11, 02:24 AM
I just bought 1990 brougham 5.7 believe it or not the opera lights work! I will post pics soon