Hello I have a great 1974 Sage Green Supreme and I love it however the Heater is stuck on. I can turn the fan off but the heater seems to always be on when I turn the fan on. It may even be blowing some hot air in from under the dash even when the fan is off.

Where should I start? Take it to a shop to get diagnosed or are there things I can try myself without a deep dive and a lot of hours?

I do eventually want to get the AC running so I don’t mind paying for a diagnosis but I’d love to be able to just get this thing off myself is possible. I’m in Texas so it’s bad enough without ac haha but the heater on too is killing me.




74 Cutlass Supreme

 

You will always feel some warm air through the floor vents- My 74 Salon has the same.
Others here can offer more specific information, as I'm not the mechanic..
I do suggest you have your system checked by a reliable (read knows older cars/Olds) shop.
One thing you can check yourself is to be sure the fan works properly in all modes, including max.. there is a thermal limiter under the hood that tends to blow that controls the max fan speed.
The others should work even if that limiter is blown. You also can make sure the door that switches from defrost to vent to floor works.
If the car has been sitting for a long time there is the possibility that critters moved in to the heater box. My 74 supreme fan didn't work- I opened the box and took about 5 lbs of 'stuff' out of it...worked fine after.
BTW, nice Supreme. There aren't many of us 73-77 guys here but there's tons of knowledge and experience.
Finally, the best thing to do is get hold of a 74 Olds Chassis Service Manual. It has troubleshooting information for most any issue.

 

Define "heater is stuck on". Is the fan running constantly or are you saying that you are always feeling hot air from the vents - and if so, which ones? And is this an A/C car or heater-only?

 

Hello all, just got back to town from a few months on the road. Will be getting back in my cutlass and get back to this tread shortly. Thanks for all the help !! I’m ready to knock out a few issues I have with it

 

Alright, so I was confusing a few different things, so here is what’s going on.

There is hot air coming from under the dash even when fan is off, I’ve seen some of yall mentioning this so I assume it’s normal.

Also, it seems that the door is stuck because when I turn the fan on it only blows out from under the dash which is why I thought the heater was stuck on. I can’t get the air to come out of the vents so that explains why it felt like the heater was stuck on.

thanks for the help for now I’ll get a service manual and start messing checking stuff.

Im about to post about my carb so more fun ahead haha.

 

That is a classic symptom of no vacuum to the dash controls - the air defaults to the floor vents. Common cause is the hose to the vacuum reservoir on the firewall is disconnected. There should be two vacuum hoses connected to the reservoir. One goes through the firewall to the dash controls and the other one connects to a vacuum port on the intake manifold (or the base of the carburetor).

https://classicoldsmobile.com/forums...utlass-138738/

 

ahaaaaa thank you so much!!