pjohns

"71" AC works fine, selector changes to vents, defrog, or floor, temp wheel cable is attached and I can hear it is moving a door under the dash. Engine was overhauled this year, could the mechanic have hooked something up wrong? Heater core not leaking. Coolant full. Vacuum lines appear to all be connected.

Any Ideas??

Alan 71

Hi pj,
Have you checked to see if BOTH of the heater hoses in the engine compartment are getting hot to the touch?
This will tell you if coolant is flowing through the heater core.
Regards,
Alan

CFD E59

Alan's right, start with the hoses to and from the heater core. It could be clogged.

TedH

My '80 L48 has a vacuum-controlled valve that is in the heater hose that runs to the heater core (in engine compartment). The valve is vacuum controlled. If the valve has been removed, disconnected or is no longer operating, you will not get heat in the heater core (it will not open to let hot coolant to flow to the heater core). I suspect the same in-line valve is in earlier C3's.

Mashman

??? - If a valve is not present, how can a hose 'not open'?

I think you have it backwards. The valve you are talking about is a shutoff valve. It is designed to stop the flow of hot coolant to the heater core when cooler air is desired in the cockpit.

The problem could very well be the valve you are talking about. They can fail closed, and block flow to the heater core. Another likely situation is that a PO has installed cutoof valves to block flow to the heater core.

Easy Mike

Can also fail open resulting in Fish Feet.

pjohns

I found the vacuum valve. Tried tapping on it to free it but no change. I did see in my Chilton manual that coolant flows through the heater core except when on max air or off position. If the hoses got hooked up in reverse (thus reversing the flow of coolant through the core) could it affect this? I can't swap them now because it's HOT. Currently the hose coming out by the thermostat is the one connected to the vacuum valve, and the one coming out of the water pump isn't.

jman1

this will cause you to not get heat....its default to blow cold air.... so if you getting cold air this will do it... it sits right behind the map pocket..... its vacum controlled... drove me nuts for almost a week

pjohns

What am I looking at here, and what did you do to fix it?

gq82

Most C3 owners would love to have your problem .

It's my understanding the inline heater hose valve only closes when the hvac controller is set to Max AC....if the heater hose is hot going to the valve but not so much coming out I'd say it failed in the closed position.

jman1

its a small vacum controlled switch.. it sits right behind the map pocket on the heater box.... when you move the heat controls u might be able to hear the cables moving the switch....but if there is no vacum to the switch you will only get cold air..... search the ac/ heater vacuum lines on this site and check them out.... my switch wasnt bad just the vaccum like was broken.....

pjohns

Turned out to be an easy fix. The vacuum valve that shuts off the coolant flow to the heater core was stuck closed. Just removed the passenger side "Gill" and it was very easily accessible. Still took 6 trips to the auto parts stores!
1. to order the valve (before I took out the old one or even was able too look at it good)
2. to pick up valve ordered
3. to attempt to get fittings to put hose barb end on threaded end because the one I took off had hose barb ends on both sides. Ended up purchasing a different valve they had on the shelf, but I didn't have my packaging so I couldn't return the original.
4. to get vacuum fittings because the size was different on the new valve. Took original valve with packaging with me but that store closed early on Sat afternoon. Had to go to a different parts store.
5. Return original valve purchased.
6. Return extra vacuum fittings purchased since I wasn't positive what I needed so I bought extra to make sure I had what I needed.



Works great now!!

fugawi

AWSOME!!!!