Van Heater question

[whiskeylivewire]

Hi y'all, never posted on this forum before but I knew I could get a good answer here! We have a 96 Ford Windstar and the heater is not working right. It will heat up just fine when idling, but when you go down the road, the temp drops and it's blowing cool, not downright cold, but not enough to warm it when we're having temps in the 0s. My fiancee has put cardboard in the front, redone the coolant and turned off both fans in there(I'm assuming you know what that means cuz not sure I do lol). We don't think it's the thermostat because it is warming up, just dropping while going down the road. Do y'all have any ideas? Thanks in advance we really appreciate it!

[Beeman]

Is it full of coolant? Is it a 3.8L engine?

[tinknal]

What is the temp gauge doing while this is going on? You could have a bubble in the system. If so this is easy to fix. First, while the engine is cold, make sure the coolant is full. Then park it on a steep incline, nose forward, and run it until it is good and warm with the radiator cap off. After it has warmed up (15 to 20 minutes) replace the cap.

[Bearfootfarm]

It could simply be the engine doesnt generate enough heat in those temperatures.
It's losing it all through the radiator.

Like Tinknal said, watch the gauge. If its "overcooling" it will go up and down as the thermostat opens and closes

[blufford]

Your heater core may be partially blocked.

[agmantoo]

whiskeylivewire
When you became aware of this problem you probably checked the coolant level and had to add coolant IMO. If this is correct I think you have air trapped in the coolant system. At idle the coolant "trickles" through the heater and you get some heat. At a higher RPM the coolant flow increases but the coolant has a problem overcoming the trapped air and doesn't flow through the heater. You can verify this by running the engine at a faster speed while not moving. The heat output will diminish but as soon as you let the engine return to idle the heat at a reduced level will return. Getting the trapped air out of the system can be a problem.Take the heater hoses loose at the engine. Open the cap on the coolant tank. Put the heater control in the maximum heat position. Pour small amounts of coolant into one of the heater hoses using the funnel. If coolant comes out the other hose reinstall that hose. If coolant does not come out fill the hose as full as possible and reinstall trying to not spill any coolant from that hose. Look at the engine fitting that the heater hose attaches to and make certain there is as much coolant int the engine as you can get in. Now fill the other hose and reinstall it trying not to spill coolant from the hose. The objective is obviously to get as much coolant in the system as possible. Check to see the coolant tank coolant level is correct. Try the heater. There is a method to use a vacuum pump to fill the system if this fails. Keep the coolant tank properly filled to prevent a reoccurrence.

Thermostat .

[Allen W]

Thermostat would be my guess. Most small cars have enough radiator capacity to cool the coolant while driving with out the fan. When you are parked your not pushing air over the radiator but driving you are. Took me awhile to figure out what was going on when the fan motor quit on the wifes caravan. The only time it got hot was idling after she drove it.

[Ken Scharabok]

The heater on my 84 Ranger quit. Took it into a garage and had it back flushed. Out came about 25 years worth of brown gunk. Guy then flushed out entire system. Ran brown for several minutes. Works like a charm now as best it can within a now drafty cab.