Heating Issue diagnosis

[trogdune]

Hello all!

 

I'm trying to get to the root of my heating issue.

 

4.0L manual

89 Comanche Pioneer

 

So far I have done the following

-Flushed heater core

-Bleed cooling system

-verify my thermostat works

-verify my fan works

 

So my heater does technically work but it's quite pathetic in terms of how much heat I'm getting in the cab. Maybe just enough to defrost the windows when the temperature drops but not at all enough for a comfortable ride. My hoses are running hot and my thermostat is kicking on when it's supposed to so I'm at a loss.

 

Does anyone out there have any ideas as to what it could be!? 

 

[eaglescout526]

Have you verified your vac connections? The heater is actuated by a vac operated valve. That hose has been known to deteriorate and not open the heater valve to get heat into the cab. It sounds like it’s working but not enough to get full use of the heater core. 

[howeitsdone]

Make sure your vacuum is good to the control valve and that it fully opens

 

[Eagle]

Duplicate threads merged and purged.

[cruiser54]

what temp thermostat do you have in the truck?

 If one of the heater hoses at the firewall, or both, are cooler than the heater hoses at the front of the engine there's an issue with the valve or the core. A fancy testing instrument like a bare hand will help verify this. 

[gogmorgo]

Make sure the blend door is fully opening. There’s a cable going to a lever under the dash in the passenger footwell, above passenger’s left foot. Should move with the temperature slider. Sometimes the cable slips or comes off. 
 

[cruiser54]

this^^ also