No heat 97 t100 3.4

No heat , onlyblows cold
Tried flushing heater core had water flow right a way
Flushed system ,pretty clean already
Changed thermostat and is in correctly
Help

 

Blowing cold at the floor or upper vents?

Air control damper stuck (blend door) stuck on the AC side?

Is the heater input line hot to touch, warm on the output side?

 

It blows cold vents for sure and floor I think the valve on the fire wall works

 

I think you may be on something about the AC door

 

How do I get at that ?

 

Check the bypass valve in the engine bay. When you go from hot to cold on your switch you should see a cable move the valve. Could be the linkage or even the knob. Could also be thermostat issue.

 

Check the heater hoses, both should be hot. If they are you have an air flow issue. If not you have a water flow issue.

 

Could it be a weak water pump , it does not over heat

 

Water valve on fire wall in engine compartment works
No leaks anywhere
I flushed heater core with garden hose and water comes out full force
Could heater core still be at fault?
Is my water pump going bad ?

 

If you aren't over heating I'd say your water pump is fine. They don't really wear out flow wise they just start to leak around the shaft. Probably a good idea to inspect the blend door in the air box behind your dash. Sounds like it isn't directing the airflow to the heater core.

 

Water pump won't effect heat. I agree with others. Sounds like a blend door/vacuum problem.

 

Could it be the sending unit the the guage sending unit the temp sending unit

 

No.

 

I'm stumped

 

BLEND DOOR! CHECK THE BLEND DOOR.... AS IN TAKE OUT YOUR BLOWER ASSEMBLY AND LOOK AT WHERE IT INTERFACES WITH THE HEATER BOX AND SEE IF THE DOOR MOVES. This is what we've all been saying, it matches your symptoms.

 

I took apart center of dash and air duct tube to the left of center and can see all levers working can stick my hand up and one door opens and a top one opens is there more I should look for ?

 

The heater core box is the one most centrally located, right behind the actual controls for the heater. In the very center of it there is a single vertical door. This is the one you need to verify the movement of.

 

ChrisFix did a great video on this. According to your symptoms it's probably the blend door.

 

I'm baffled as well. Not by the problem though.

 

Blend door failure.