heater blowing cold

[chevy6673]

blowing only cold air most cars this means time for a new thermostat ..does this hold true with vettes the a/c is intact but compressor is missing ..its going to be cold here soon ..would like to keep driving till the snow comes the i put her away..

[petes74ttop]

Hi a thermostat lets water flow after in hits its rating, so you might consider a 180* Robert Shaw to get the temp up enough to keep you warm.

No heat at all could be-
Heater hoses joined together to bypass heater core.
Bad heat control switch, in the heater hose line.
No vacuum to heat control valve.
Bad heater door control valve or no vacuum supply from thumb switch.

That's a few places to start looking, Pete.

[72VETTE454]

I would check the anti-freeze level. Heater blowing cold is a sign of low anti-freeze. A thermostat stuck shut would cause over heating, and definitely not your problem. A thermostat stuck open would eventually warm the engine up, and you would be blowing hot air. It's not the thermostat...IMHO. Good luck.

[DarkShark]

Originally Posted by petes74ttop

...Heater hoses joined together to bypass heater core.
Bad heat control switch, in the heater hose line.
No vacuum to heat control valve.
Bad heater door control valve or no vacuum supply from thumb switch...

I'd follow Pete's train of thought. Otherwise, you'll spend money somewhere else and still have a cold car.

[chevy6673]

Originally Posted by petes74ttop

Hi a thermostat lets water flow after in hits its rating, so you might consider a 180* Robert Shaw to get the temp up enough to keep you warm.

No heat at all could be-
Heater hoses joined together to bypass heater core.
Bad heat control switch, in the heater hose line.
No vacuum to heat control valve.
Bad heater door control valve or no vacuum supply from thumb switch.

That's a few places to start looking, Pete.

ok cked thumb cables ,there is a metal block in the middle of one hose it has a turn screw on top whats that for ?? so you say theres a heat control switch in a heater hose witch hose ..they are not bypassed appear to be hooked up right ..wear is vacuum heat control valve maybe under dasd ??? thanks 4 the help it does look like a gasket on one side of water pump is lecking but pump seems ok not lecking from drain hole