My heater doesn't seem to get warm, I think it may have something to do an air actuated lever on the firewall inline with one of the heater core lines, I can't figure out why it's not working though??

1991 diesel 4x4 ac equipped

 

Not getting any warm air, do I need a heater core flush, one of the heater lines stays cool for a while or until the truck is driven across town... Vent doors seem to work under dash, I did have alot of leaves to clear out of the cores ducting area...

 

does it look something like this? this is a heater control valve.

 

I was thinking check the temp of the core by opening the vent area up and reaching in, would this tell me if I was getting adequate flow through the heater core if it was hot and what temp should it be??

 

Similar but with only one airline port and it gets vacuum but doesn't actuate the lever

 

the first door that slides up just opens to the cold air intake. there is another door in the heater box that allows the cold air in to adjust the temp coming out of the vent. with the temp set to cold you should probably reach in and feel if it is warm but i think the easiest way to tell would be to feel the heater hoses after it has hit operating temperature. both hoses should be about the same temp but if one is hotter than the other there may be a problem somewhere.

 

Does the thermostat have to pop open to make the heater core warm??

 

no. the heater core should get warm even with the thermostat closed.

 

You can tell winter is here with all the heater questions. The heater water control is vacuum operated in the 91 with A/C. If the engine is warm the thermostat will be open. But the thermostat does not control the heat except in the engine. With the heater controls on, both heater hoses should warm up pretty much the same once the engine temp starts to rise. If the hoses don't get warm there is a blockage somewhere. The water control valve is in the water heater supply hose between the water pump and the heater core inlet. Possible places of blockage are 1. the water pump outlet, 2. a collapsed heater hose, 3. a malfunctioning water control valve, and 4. a blocked heater core.

STEP 1. You can disconnect the heater hose that comes from the core at the water control valve and plug the hose. Point the valves outlet into a bucket. With the heater controls off have someone start the engine. When the heater control in the cab is activated briefly you should get water in the bucket. If you get flow 2 & 4 are possibles if not 1, 2, & 3 are possibles.

STEP 2. (no flow from STEP 1) Remove the valve and direct the hose into the bucket. Start the engine very briefly to check for water flow. If you get flow the valve is bad, if not 1 & 2 are possible problems.

STEP 3. If you have flow from STEP 1 reassemble these hoses and disconnect and plug the cores outlet hose. Connect a spare piece of heater hose to the cores outlet and direct that into the bucket. You should get flow into the bucket when the valve is activated. No flow indicates a plugged core.

 

I reAlly appreciate the input thanks all...

Seems pretty odd that when I turn the heater on the air Actuated diaphram in the heater line closes stopping coolant flow through the core... Does this sound rite?? Cause that's what mine is doin...