Weird Heater Question 1994 Ford Explorer LE

[VA7LFD]

Weird question, by the way thanks for all the info. and help from all of you here in keeping my 94 Explorer Limited Edition running the past many years.
Here it is I have not been able to get proper heat in the passenger compartment. I have no leaks from the heater core or cooling system itself. The blower fan works perfectly. I went to check the vacuum valve for the heater and I actually snapped it ( cheap plastic piss me off ) I am in the process of going to buy a new one tomorrow or next few days. So I can operate the vehicle I pulled the valve and directly hooked the hoses from the water pump to the heater core thinking that will verify my problem. I still have the same problem it doesn't come up to the proper temperature when heat is on. Yet if its a really nice day say 55F or above the heater works unbelievably well and right up to temp. Again there are no leaks anywhere. Oh almost forgot the A/C is not working. There is a hole in the condenser and the system has no refrigerant in it. Don't really care about the A/C right now. Just at a loss.
Should I check for air in the system, thermostat problem, controls for the heater temp. adjust are faulty? Anything else?

Thank you from Vancouver BC. Merry Christmas to all....

 

[Roadrunner777]

One thing that comes to mind... there is a door in the HVAC system that determines if you are recirculating or drawing fresh air from outside. As I recall, this door is operated by vacuum, so in order for it to work properly, there has to be good vacuum to the climate control panel, where it is controlled, and then on to the vacuum dashpot motor. I'm not saying this is it definitely. One reason why I am hedging is because it is a complete royal PITA to get to the recirculation motor and door assembly. But I think a quick easy thing would be to check the little vacuum tubes under the hood, right side firewall. If one of them is cracked or loose in some way, there may not be enough vacuum available to operate the door.

Or it could be something else entirely! Air in the coolant system could do this too. A problem with the cable operated hot/cold blend door could do this. The heat has never been great in 1st gen explorers, but you have had yours for a while so you know right from something wrong... just saying. I'd take a quick look at those little tubes. They get brittle and crack after decades under the hood.

Good Luck!

 

[VA7LFD]

Where would this door be located? I will check for vacuum at the controls too. I will pull them out today...

 

[shran]

That door is accessible if you remove the blower motor, reach into its cavity and basically straight up from here. It pulls air from the cowl. Repairing it, if broken, however involves removing the dash (which is really not hard.) It is activated by a little vacuum deal below the glove box and right against the body - it has a black vacuum hose running to it.

Kinda sounds more like a heater core issue, plugged up maybe. You don't necessarily need that heater bypass valve that you broke... prior to 93, they didn't exist on RBVs. It makes the AC work much better, though.

 

[Gary Crist]

I had a 91 that had a ****ed open TStat. No heat on a cold night
but, warm during the day.

 

[VA7LFD]

I replaced the heater core valve with a new one and flushed my rad. The valve doesn't actuate at all but when I adjust my temp from cold to hot in vent mode temps goes from 70F to 110F. Yet I don't see the valve actuate. I'll leave it the way it is as it's working way better but still not 100% I don't get any vacuum at valve from the little orange vacuum hose. Also my heater fan is intermittent which I know what the problem is which can be fixed easily from Rockauto. Thanks for help everyone...

 

[Gary Crist]

I had client at a Lincoln Merc dealership in Kansas that took a lawn mower
choke cable and hook it up to his valve. We all giggled but, it worked....

I had to take the dash apart and remove a few 30-06 shells from the heater....

Long live deer season.