yelo80vette

I recently lost heat in my 1980 L48. There is no typical evidence of a bad or leaking heater core. Plus I'm almost sure it isn't the vent doors. Has anyone else had a problem like this... or possibly know of a solution?

henrikse

Is it blowing cold air? If so the vacuum to the door that controls?

ntfday

My only thought is a faulty heater control valve unless of course the water pump went south, but you'd know that from a major overheating problem.

Easy Mike

Check the hot water control valve under the hood. It may be stuck closed.

SwampeastMike

It's on the passenger side of the engine compartment ahead of the blower box and A/C accumulator. It has two heater hose connections and one very small vacuum line leading through the firewall.

yelo80vette

Yes. The air coming out now is, well, not cold particularly. It's pretty much whatever the outside temperature is.

76bomb

Basic question... is the coolant level low?

ntfday

Have the heater hoses been replaced? If so with the proper hoses? The hoses are preformed and if regular hose is used they could collapse cutting off the water to the heater core. If the coolant was low enough that you're not getting any heat then you would have a MAJOR overheating problem. As I said earlier you problem,IMHO, lies in either the hoses or the heater control valve. BTW, these are the hose you should have,
https://www.ebay.com/itm/1968-1982-C...tTjkAJ&vxp=mtr

yelo80vette

Nope. Fresh antifreeze always kept at the proper level.

yelo80vette

Nope. I've never replaced the heater hoses since I've had it and they're still in good shape. I believe I'll probably begin my investigation at the heater control valve. Thanks for the link !

ntfday

This should be what you're looking for, be sure you're getting vacuum to the valve.

https://www.ebay.com/itm/HVAC-Heater...JafLde&vxp=mtr

yelo80vette

Ah ha. Great. Thanks for the lead.