: Another "its getting hot" A/C Thread...



01devilledts
05-17-09, 07:46 PM
OK so its really hot in AZ, and just had the black leather seats re-done in the black 68 SDV that im working on. (already burnt my leg once)

My question is, where do I start on diag. the ac system. As of now, when i move the climate control slide nothing happens, and the plug on the compressor is disconnected. I noticed the orig. owner had installed a toggle switch under the dash that goes to something on the firewall (i know that's not a big help but the car is at my shop right now and cant go look at it real quick.)

Any suggestions on where to start ?

Thanks in advance

Highway Star
05-18-09, 02:24 PM
Have you re-connected the compressor wire/s to see if the clutch will kick in? In a perfect world you might get lucky and it would have enough freon and oil to get you cooling. But more than likely something is amiss. For a 40+ year old vehicle, I'd just get a new compressor, accumulator and other necessary components and get it converted.

01devilledts
05-19-09, 12:48 AM
Yeah I tried to connect it, and still nothing happens.

So im guessing since there inexpensive I should replace the blower motor?

I planned on buying a reman. Compressor, dryer, expansion valve, and o rings.

Should that be my first step?

Highway Star
05-19-09, 09:57 AM
If the blower motor is working properly, and isn't hard to get to, it might be ok to leave it alone and replace it at a later time. I don't recall the blower location on the '68s. The one on my '79 has easy access on top of the heater/ac box. If you get a reman compressor, get one from a reliable company. I've heard some of the remans have a high failure rate.

Not sure if you're familiar with this site, but it has loads of useful info: http://www.autoacforum.com/

They also sell ac parts, check the link on their forum. They're out of Arizona.

dirt_cheap_fleetwood
05-19-09, 11:02 PM
If you can get a new one do it. I just bought a new compressor from Napa for the Brougham and it was only $75 more than a reman one. I have had bad experiences with many reman parts.

Test the connector going to the compressor and see if it has power and a good ground when the AC is supposed to be on. If there is no power you have a wiring issue, not a compressor clutch issue.

01devilledts
05-20-09, 12:23 AM
Not sure if you're familiar with this site, but it has loads of useful info: http://www.autoacforum.com/

They also sell ac parts, check the link on their forum. They're out of Arizona.

Awesome, haven't heard of them before, but there about 15mi from my house, so im gonna run over there on sat and see what they have to say.

Yeah, ill check the compressor plug tomorrow when I get to the shop. I want to stay with R12.

Someone was telling me about something called "freeze12" so im off to Google that right now.

Brother_B
05-20-09, 08:43 PM
Also, I don't know if you are aware, the factory service manuals are excellent for A/C instructions. I was trying to repair my '72 using my '69 manual. But the systems were not exactly the same. When my '72 manual arrived in the mail, I found the correct diagnostic procedure in seconds. It would have saved me from removing the top of my dash, but I had to do that anyway to get at my front speakers. Anyway, the point is the factory service manuals are awesome for this (and any other) repair. I think your '68 would be similar to my '69? For an example of how excellent the manual is, in my '69 manual, Air Conditioning and Heating is Chapter ONE, and that chapter is 94 pages long! Cadillac took A/C very seriously, man! If you read through that chapter a few times, you will learn a lot. If nothing else, a technician that you end up paying would love to have a look. It even has instructions for rebuilding the compressor.

To your original question on where to start, I would run a jumper wire from the + battery terminal to the compressor to see if that makes the clutch engage. The compressor probably has a connector for two wires. One is the ground, probably grounds near the ignition coil. The other is the power wire. If the compressor clutch engages with 12 volts applied, I would let it run for a few seconds and then observe the sight glass to see if there is R-12 running through the system, if that looked OK, you should be very happy. Then figure out why the blower motor is not working.

If you come up with some specific questions, I can try to look them up in my '69 manual.

There have been heated discussions on the forum about R12 replacements. Some people love the Freeze12, others hate it. I think someone said it's mostly propane. Search the old threads. I don't have an opinion, but I like the idea of sticking with R12. If you have bad leaks, though, eventually it would get expensive to keep charging the system. Starting from zero, I would think you would need about $130 worth of R12, but maybe you're lucky and you still have a bunch in your system.

Highway Star
05-22-09, 10:42 AM
Also, I don't know if you are aware, the factory service manuals are excellent for A/C instructions. I was trying to repair my '72 using my '69 manual. But the systems were not exactly the same. When my '72 manual arrived in the mail, I found the correct diagnostic procedure in seconds. It would have saved me from removing the top of my dash, but I had to do that anyway to get at my front speakers. Anyway, the point is the factory service manuals are awesome for this (and any other) repair. I think your '68 would be similar to my '69? For an example of how excellent the manual is, in my '69 manual, Air Conditioning and Heating is Chapter ONE, and that chapter is 94 pages long! Cadillac took A/C very seriously, man! If you read through that chapter a few times, you will learn a lot. If nothing else, a technician that you end up paying would love to have a look. It even has instructions for rebuilding the compressor.

Very good advice! Everyone who has one of these older classics needs a service manual for their specific year. I just topped off my AC with some R-12 recently, and used my manual for doing a test/s on all functions of the climate control system. And speaking of the climate control system, it must have been engineered by rocket scientists! To those who need a manual, many show up on Ebay at reasonable Buy it Now prices, so don't get into a bidding war on them.

01devilledts
05-31-09, 07:52 PM
Thank you everyone for all the help so far....

Highway Star, I do have the factory service and shop manual for my model it is very informative when it comes to replacing parts you are correct.

As of now Compressor, Dryer, Lines, Expansion Valve and Blower motor are all new and installed. System has been vacuumed down and pressure tested. (no pressure lost) Refilled using Freeze 12. I get 58* air but only out of the top "defroster" vents.

I'm guessing i have a vacuum problem to move the door so it will blow through the front vents. My manual has all the vacuum lines and diagrams but im at a loss when it comes to actually doing anything with that info.

Anyone know about those systems?

01devilledts
06-01-09, 11:12 PM
Ok, I think I got it buttoned up...

The mode door vacuum line was capped off and that is what was keeping it from changing to the front vents.

Now it seems like it works fine, other than the toggle switch the previous owner installed under the dash that jumps the two connections at the master vacuum switch under the hood.

Without that switch hooked up nothing comes on, but i opened it up and it doesn't look bad at all, and nothing that doesn't look like its out of place. i would really like to remove that switch from in the car.

any suggestions?

Highway Star
06-02-09, 10:08 PM
Sounds like you're getting there. I'm puzzled by the switch (as I'm sure you are).

Brother_B
06-04-09, 11:51 PM
You said nothing comes on without the toggle switch - no blower, no compressor, nothing? Or just no blower?

01devilledts
06-06-09, 04:32 PM
You said nothing comes on without the toggle switch - no blower, no compressor, nothing? Or just no blower?


Just the blower, the compressor engages still but without the circuit being completed between the two connections on the master switch, The blower motor doesn't kick on.

WMD
06-06-09, 07:49 PM
When all systems are intact and operating, the Master sw. will close and enable the blower circuit when any one of three conditions is met. These conditions are.....The Thermal Vacuum sw. located on the Water Valve is warm enough to send vacuum to the Master Sw., the Control is set on Defrost or Vent, or if the system is commanding Max. cooling. The system is designed this way so that you are not hit with icy air when the engine is cold and the system is in the heat mode, the blower will then only start when the coolant is warm enough. It will start immediately in Def. and Vent to clear the windshield as a safety feature however. Finally it will start immediately when the system is calling for Max. Cooling. As I mentioned above, the system must be intact and all support features operating as designed. The Comfortron is a sophisticated and beautifull operating feature but can be a nightmare to repair without the proper 68 Manual and patience.
wmd

01devilledts
06-06-09, 08:53 PM
. The Comfortron is a sophisticated and beautifull operating feature but can be a nightmare to repair without the proper 68 Manual and patience.
wmd

Awesome....

I have the Factory Service manual, hopefully thats what I need ...

First off, all the vacuum lines are connected and good, except one that goes to the heater valve. it is broken off the master switch, but i cant find anyone that has the master switch for me to purchase.

Second, as of now the heater core is by-passed for some reason, im waiting on the new one to come in so i can change that. Would that cause the master switch not to function?

WMD
06-06-09, 09:50 PM
If you can't repair the Master sw.,look in Hemmings Motor News for older Cadillac parts suppliers. That hole in the sw. will disable the blower circuit but the heater core will not.
wmd