Okay,
So I've searched the forum and haven't quite received all of the answers I'm looking for. It's cold out and took my wife's Expy out for a drive and found the heater is not working well. Here is what it does.

Front heater blows luke warm air when blower is on low. If I turn the blower to high, it blows cold air.

If I turn the temp control **** the slightest from full hot it blows cold. If I turn it all the way to cold, it's really cold. I have the manual controls.

Rear heat does the same thing as the front unit.

I checked the coolant level in the reservoir tank and it's good

I grabbed onto the heater hoses while it idled in the driveway. The hose that runs from the block to the firewall is warm to the touch. I can hold it, but not for long.

The hose coming from the firewall that tee's off to the rear of the truck is lukewarm and I can hold it for a long time.

The A/C compressor cycles on and off.

So, those are the symptoms. I'm thinking I need to start with a coolant flush. Thoughts????

 

You've got inadequate coolant flow through the heater core(s) loop.

Could be a restriction in that loop, a faulty thermostat, or a weak water pump.

Back flushing the heater loop is a good start.

 

If it were a blend door issue then both of these hoses would be fairly equal in temperature. So like projectSHO89 said, you're probably looking at restriction in the heater core. Backflushing it could solve the problem, but if it doesn't you're looking at replacing it. Replacing the heater core is a 10 hour job that requires removing the entire dash.

If it were me I'd start with replacing the t-stat just to make sure the temperature of the engine is up where it should be. I'd do this just to be sure and also to rule out the simple thing first.

 

Thanks guy's. I'm going to take it in to get the coolant system flush done first and see if that fixes it. Next step will be replacing T-stat. Neither of the heater cores are leaking so hopefully they're just a little gummed up.

 

Okay,
I had the coolant flushed today and here is where it stands.

Rear heat now blows hot

Front heat blows warm when on any setting other than its highest

Switching from Panel to Panel/Floor causes it to blow cold

Both heater hoses running to/from firewall are hot to the touch

So am I looking at a blend door or controller issue?

 

That is correct.

 

your lucky...i had core replaced ran me 700 dollars.

 

I had the same problem with heat. I have a 2000 Ediie Bauer with the 5,4L Digital climate control *****. Heat adjustment from 60-90.

My problem was barely warm heat. Replaced the thermostat did no good. Fast forward 6 months the heater core is leaking inside the truck.

I take the truck to the shop and get a new heater core installed, the problem the heater core is leaking, something about plastic, maybe the connectors or the tank. The cooling system was full of anitfreeze so im sure the heater core didnt rot or rust. It failed due to it's poor design.

New heater core in I get red hot heat. When I turned it down to 60 still red hot, take it back to the shop. They had to calibrate the heat system as what he told me. Now it works cold at 60 and hot like it never had at 90. All these heater problems could be the heater core, or get your heat system checked and calibrated. Good luck.

 

Same kind of issue. Heat is not HOT. But also temp gauge never reaches middle of gauge. Stays closer to cold. Are these related issues?

 

Your issue sounds like a thermostat problem.

 

Ditto on the thermostat being an issue, it's stuck open.

 

Thanks for the guidance!

 

Thank u 2!