Vehicle:

1984 Toronado
307 V8 TH325-4L


This thing has the tempmatic temperature control system.

The issue I am having is it remains at full hot, all the time, regardless of temperature setting or duct setting (Defrost, floor, whatever).

I do have a vacuum leak under the dash somewhere and am wondering if that might have something to do with it. I've had the vac leak for a couple months now and it hasn't done the full hot thing until a day or two ago.

I don't mind the heat on the colder mornings, but in the afternoon it's getting a bit hot for comfort in there.....

 

Hello I have the same issue just with a different car but a 307 and same tempurmatic. I used a T from a vacum line and attached it directly to the vacum pump that operates the flow of water. It is on passenger side rear of engine

 

There is a vacuum checking relay valve located on the programmer. It regulates vacuum to the diaphram that operates the mixing door and keeps it from cycling due to changes in engine vacuum. Just about every Tempmatic I've ever seen get stuck in full hot (or full cold for that matter) had a bad vacuum check relay.

I used to have the part number memorized, and the Buick-Pontiac dealer here used to keep a minimum of three in stock at all times, if that's any indication how often the things fail.

Right now my Cruiser wagon is having the same issue, I just can't get back in town to order one before the damn GM dealer closes for the day (What kind of dealer parts department closes at 4:00 PM? ). So I have rigged it with a vacuum vent line. It sticks in hot, I pull the golf tee out of the vent hose and it goes back to normal operation.

And that was a trick I learned from an Oldsmobile Zone service manager.

 

How bad is that turd to get too? I had the glove box out and couldn't get to it. I am going to ASSume that I need to pull the lower dash kick panel off to get to it.

After the kick panel is off, how hard is to to get too?