I have a 1972 Cutlass Supreme rag top, and I had heat up until about a week ago. It worked great, but now it doesn't blow. The defrost still blows hot air.

The only thing i can think of was the last time I shut the car off, I turned the heat to low, but I didn't change the slider that selects "Off___Defrost___Heat" to Off.

Any suggestions would be appreciated, Thanks!

 

The only thing that differentiates defrost from heat is a door that redirects the air either to the defrost duct or the heat duct. Some cars use a cable to move the door and some (mostly A/C cars) use a vacuum motor. For some reason the when you move the lever to heat the little door isn't moving and redirecting the air flow.

Crawl under the dash and see if there is a push/pull cable going from the control lever to the heater box. Follow it and it should go to a little arm on the heater box. While watching the end of the cable move the heater/defroster control and see if it's moving the actuating arm.

If it's a vacuum control you could have a bad vacuum motor, bad or detached hose.

Scott

 

If it's an AC car, make sure the vacuum hose is attached to the vacuum reservoir ball on the engine side of the firewall.

It's the thing in the upper right corner of this photo:


https://classicoldsmobile.com/forums...i-missing.html
2010OldsACcomponents2.jpg

 

Let's start with terminology just so we're all on the same page.

Does "now it doesn't blow" mean that the fan doesn't turn on in the HEAT position, or that the fan runs but nothing comes out the heater outlets? If the latter, does air come out anywhere else in the HEAT position? Also, is this a heater-only car or an A/C car, since the controls are completely different.

 

Based on the OPs description it's obviously a non AC car



If the fan is only operating on low, I'm betting it's the resistor pack on the plenum.