Looking for the Manual AC/Heat troubleshooting supplement

[LithiumCobalt]

This book is a supplement to the original factory service manual. Does anyone have one scanned that they wouldn't mind sharing? I have the one for the ATC, but since I have manual AC, that doesn't do me much good.

[Dan Szwarc]

The forum has a HVAC manual for 1967. I think. And I think it includes all AC. Feel like a making donation to support us?

[LithiumCobalt]

Dan, I think you know I would support the forum. What does the cover look like?

[Dan Szwarc]

Crap. It says Automatic Temperature Control version!

I'll send you the link to the 66 HVAC manual. It should be the same for 67.

If you find it useful, you can send me a fair amount in exchange. Deal?

[Dan Szwarc]

I sent you a link to the 66 HVAC manual that covers the manual AC. See if it helps you out.

What kind of problems are you having? Most are vacuum leak-related.

[LithiumCobalt]

Thanks Dan. The scan of the 67 ATC manual is probably the one I sent to you for scanning a few years back. Thank you for the link. I will check it out tonight. Will send you some $. I just got my car so haven’t had much chance to dig into it. Heat works fine, blend doors change position, and fan blows fine, just no compressor engagement or cooling. Going to have to figure out how to attack it. Worked a bit on vacuum problems yesterday. Dug into the lock system....pulled off the left kick panel and about four vac lines were flopping in the breeze. No wonder it didn’t work.

[Dan Szwarc]

On the ATC version, lack of engagement of the compressor could be caused by the relay that triggers the clutch inside the MCU. This is controlled by R2 inside the MCU.

This is the G-Y wire coming out of it. It is tied in series with the de-icing switch and also powers the idle compensation solenoid.

First, confirm that the solenoid is coming on. If not, check for voltage at the de-icing switch. If you have 12V on one side, bypass it (jump it.) If that engages the clutch, you have a bad de-icing switch.

If you have no power coming to the de-icing switch, then R2 inside the MCU could be bad or there is a bad connection.

I'm guessing the outside electronics on the non-ATC AC is the same as the ATC version. The differences are inside the car with all of the sensors.

Also, based on the 66 manual, it looks like the wiring colors are the same for manual AC compared to 67 ATC. Don't know about Relay R2 and if it is inside the MCU or not on the manual version. It may be just a switch in the control head since manual AC doesn't need to switch between heat and cool depending on inside and outside temperatures. So, there's that.

[LithiumCobalt]

Had a closer look and I was mistaken. AC compressor does engage so that proves out the deicing/clutch circuit. Whether it still compresses, I do not know. I've got one of three things - bad compressor, no refrigerant, or bad expansion valve. I will have to take it to my AC guru to see if he can figure out what it is since I don't have a set of gauges. No use to replace good parts, but I feel like I should simply replace the expansion valve and drier for reliability. Will have to take it in and see what they recommend. Most of the info in the supplement is already in the regular service manual - I sent you cash anyways.

[Dan Szwarc]

Thanks! Good luck on fixing it. Since my 66 has no AC, it's one thing I know little about.

[TonyC]

Well, that sounded like a much-simpler mystery than the one I had that confounded me for over a year: The heat working fine until about 50 mph or higher, when it went cold with no adjustments done. I went through the entire dash trying to track down the cause of that, to include buying spare control panels and a "brain" box, all to no avail. Then the engine went comatose. Fast-forward 8 months, still had the same problem even after the rebuild, so that ruled out a failing engine/bad vacuum source. Then I came across the cause one day when that same thing happened; I stopped and opened the hood, only to notice that the blend door was in fact open, wide open, to let in heated air, meaning all the controls were in fact working as they should...but the air going through still wasn't heated. That told me the heater valve had shut and cut off coolant flow to the heater core; to test that theory I pulled it out of the equation completely—removing it, splicing the two hoses together, and capping off the vacuum tee—and the heat remained operational and constant at highway speeds once again. Then, on a hunch, I re-installed the valve in reverse order from the manual's rather-unclear guidance, with the inline fitting pointing to the intake and the side fitting pointing to the heater core. The system continued to work as it was supposed to. Mystery solved.

While going through all of this, I was also wondering about that "heater-water-control switch" that was attached to the control panel, a piece unique to the manual-A/C setup, not used on the other two HVAC options, and never properly explained in either shop manual I have. I did not understand how it was supposed to work, nor why mine seemed to be not working even though I couldn't really understand how it was supposed to work. With one of the spare manual-A/C panels I bought, I found the answer to my questions; now I fully understand what that switch is supposed to do and how it's supposed to work (although that was not the actual cause of my loss of heat on the highway). My original had somehow bent its tab with the rubbing block on it, so it was not flipping on or off with the dial; I've since straightened out the tab, and it now operates with the dial properly.

I don't know if that supplement has those explanations in them; if it doesn't, perhaps I should emulate Ron Baker and write up my own supplement and offer it for sale. On the other hand, with my discoveries already posted here free of charge, who'd wanna buy one?

[CaptainDave]

Dan, I'd like to get a scan of that '66 HVAC manual. Happy to send an additional donation in exchange. Please LMK. Thanks.