Louglutz

I just purchased a 68 Vista Cruiser 350 a/c car. Everything works but the heater. The blower motor blows for the a/c defroster and vent on all speeds but no hot air. When heat is selected the blower motor doesnt even come on. Any help?

Greg Rogers

You can see if you have power to the motor when you turn on the fan switch, If you do and you have good ground then go from there. I assume you have already checked fuses...

Oldsmaniac

To get heat the Hot/Cold slider must work and open the damper door and if there is a heater control valve on the intake manifold that is vacuum operated it must work.

cdrod

I think you have a problem with a vacuum hose or the heater control valve in the intake manifold is not working. I don't have any info on '68 models but I do have something for the '69 models. I have attached a pdf from the '69 assembly manual that show the vacuum hoses for the AC controls. I would test the following items first:
1. Test the vacuum tank on the firewall to see if it has vacuum from the engine, and that it will hold a vacuum.
2. Check the watervalve at the back of the intake manifold to see if it has vacuum.

Happy hunting!

frankr442

If the fan works in the defrost mode but dies when switched to heat, there must be something wrong with the blower switch or the entire htr/ac control.

Louglutz

Well my dumbass didnt realize the air is coming from the lower vent under the dash but that is working. The air still is not as warm as it should be. It's not cold but it ain't hot either.

frankr442

OK, so if the fan blows but the air's not hot enough, see posts #3 and #4 and also check your thermostat. Maybe it's stuck open.

joe_padavano

The very first thing to check is, do you have the correct heater control valve? The 1972-earlier A-body cars use a valve that is normally closed and opens when vacuum is applied. The 1973-later A-body cars use a valve that is normally open and closes when vacuum is applied. As with many Oldsmobile replacement parts, most of the aftermarket catalogs have these listed incorrectly. Even if you do have the correct valve, it is not uncommon for the valve to corrode and stick. Finally, if you are not getting air routed correctly, it is likely due to incorrect vacuum hose connections or low vacuum in the system. This will ALSO prevent the heater control valve from opening, causing the temp problem.

Louglutz

Vacuum leak to the heater control valve. Thanks for the help! I've never had a heater blow cold before with everything else working fine so I learned a lot about heater control valves just from these replys.