1986 Toronado Heating Problem

[amartin1718]

Just picked up a well-used '86 Toronado as a winter daily driver. It's got almost 190,000 miles and I think I'm the fifth owner, but she's in decent shape. The only real mechanical problem is that it's badly in need of some new shocks/air struts.

Anyway, my heating problem. The car was blowing nice warm air when I picked it up, and after I'd driven for half an hour or so, it got too warm, so I turned down the temperature and it blew cool air. So far, so good.

Then, an hour or so later when night fell and it cooled off, I wanted some heat again, so I jacked the controls up to 75 or something.

...And there was no heat. Maxed out the temperature; nothing. Set it to cold again, then warm. Nothing. Turned the whole unit off and back on; nothing. Pulled over, turned off the car, started it again; same story. Even tapping the side of the dash like an old TV didn't work.

Now from looking around forums like these I've read that people's electronic dashes have given out and none of the gauges (or the HVAC controls) work. My dash is working fine, and the previous owner had it rebuilt (think < 3 years ago). The dash lights sometimes don't turn on at night, but I'm going to check out that sensor in the defrost vent for that. I can still control everything just fine, but when I set it to be warm, it keeps blowing cold air.

So, I can't see it being the dash itself, because everything else works fine. I can't see it being the heater core giving out during a 30-60 minute period where I didn't use it.

Any suggestions? Possibly the little door in the air ducts that blends the warm and cold air?

[maxwedge]

Welcome to AF. What does it actually do or not do, blower quits, cold air, what vent does it come out of. Nothing?

[amartin1718]

Sorry, I guess I shouldn't have used the word "nothing" that much.

The air still comes out of whatever vent(s) I set it to, and the blower itself is fine. What happens now is that it always blows cold air, no matter what temperature I set.

[maxwedge]

There is a programmer that operates the temp mode door, this is controlled by the hvac control head based on desired setting, outside temps and in car temps, any one of these components could have gone bad, there is way to access the codes or command the control unit in that that car thru the a/c control panel similar to Cadillac, you really should have a full shop manual to tackle this.

[amartin1718]

Would the Haynes manual be good enough, do you think?

[maxwedge]

No there is no in depth diagnostics for that system in Haynes.. Alldata online manuals for 30 bucks a year is another option.

[amartin1718]

Okay, I've got a proper Oldsmobile chassis service manual on the way, thanks to eBay. But, since I'm impatient, I did some digging online to discover how to pull the codes, and also a list of possible/common codes on a forum dedicated to the Cadillac Eldorado (which I guess was one of several cars that had the same BCM unit).

I got these two codes, which, given what you said about the programmer and such, are kinda interesting:

B337 - Loss of HVAC Programmer Data (Cleared, Hasn't come back)
B440 - Air Mix Valve (Door) Circuit Problem (Current)

Plus one that I'm not sure what it might affect:

B552 - Keep Alive Memory Error (Cleared, also hasn't come back)

So, what do you think? Will I need a new programmer unit? Or is there some way I can override the system? If there's an override that always makes it blow heat, that's fine - the A/C compressor's shot anyway, plus it's a winter car for the forseeable future.

And what about that Air Mix Valve circuit code? Is the temp mode door shot? Or is it an actuator, or relay? I'm basically useless when it comes to the electrical side of things.

[maxwedge]

552 is not an issue, when you get the manual you will see you can command the mode door thru thru ac control head, the actuator could be bad or disconnected, if you command the door and no action you will have to get to it to see whats what. Based on the codes the programmer could be bad also. These systems, from day one, were problematic.

[amartin1718]

Well, I'm still waiting on the manual, but the heat decided to come back the other day. And, when I change the temp settings, it will switch from cold to warm air and back. So, I'm thinking loose connection, and one of these times I'll go over the wrong bump and it's gone again. I suppose I'll get in at it once I get that manual.