Heater control valve?

[Cat Fuzz]

Do I have a valve on my 94 3.2L Rodeo that actually shuts off the coolant flow to the heater core? My manual simply says that "early models" have the valve and later ones just have doors that shut off the heated air. I'm not sure what they consider the cut-off for "early models".

If I do have one, how is it operated? Vacuum? Electric motor? I've had problems with the heat going cold while idleing but it seems to be getting worse. I used to be able to just rv the engine a little bit to get heat while sitting at a light, but now I seem to be taking longer and longer to restore the heat. I figure it has to be a coolant flow issue since the levels are fine. If the valve is vacuum operated, it may be failing requiring more and more vacuum to operate properly.

[Gizmo42]

When the engine is cold open the radiator cap and check your coolant level. I'll bet its low.

Even if there is coolant in the over flow tank it could be really low in the radiator (doesnt always suck it all in).

[Cat Fuzz]

I thought that might be the problem but it isn't. Coolant is full.

[Gizmo42]

Ok, so I would have lost that bet. Every time I've heard that symptom its been a low coolant issue.

My haynes manual doesnt mention valves, only doors and levers.

Temp Control Lever (hot/cold) - left side of heater core
Air Selector Control (floor/vent/defrost) - bottom right side of heater core
Air Source Control (fresh/recirc) - blower housing

1. To adjust air source control set lever to recirculate. Set damper to recirculate position (towards firewall). Install cable and clamp it in place.
2. To adjust temp control set control to cold. Move lever on heater core to cold position (up). Install cable and lock the clamp while applying slight pressure on outer cable.
3. To adjust air selector control set dash control to defrost. Move lever on heater core to defrost position (far right). Install cable and clamp.

If its a coolant flow issue the only thing I can think it might be is radiator or heater core getting clogged with junk. Wouldnt think it would be water pump, never seen a pump decrease in flow rate with age. Normally the seal fails or (rarely) the impeller breaks off which will get no flow.

Those instructions are from the haynes manual. Hope that helps some.

[anthonyn]

I've seen the heater core assembly and there is no vacuum hose or electricals attached to it. It just mechanically operated via levers and cables (the old fashion way). Of course the blower fan is another story.

I would let the car idle for a few minutes, then feel the two hoses going into the firewall that deliver coolant into the heater core, they should be hot. If not, then they or the heater core may be plugged up.

You can remove the heater hose and using a garden hose with a spray nozzle, you can flush the heating system. But, if all else fails, you'll probably have to replace the heater core.

Also, If you find your car takes forever to warm up, then the thermostat could be stuck open.

[Cat Fuzz]

Originally Posted by anthonyn

I've seen the heater core assembly and there is no vacuum hose or electricals attached to it. It just mechanically operated via levers and cables (the old fashion way). Of course the blower fan is another story.

I would let the car idle for a few minutes, then feel the two hoses going into the firewall that deliver coolant into the heater core, they should be hot. If not, then they or the heater core may be plugged up.

You can remove the heater hose and using a garden hose with a spray nozzle, you can flush the heating system. But, if all else fails, you'll probably have to replace the heater core.

Also, If you find your car takes forever to warm up, then the thermostat could be stuck open.

Thats a good idea to feel the heater hoses to see whats going on. The car does warm up quite quickly, so I know its not a thermostat problem. Thanks everyone.