Where's the heat?

[3Kp]

I have a 91 F 350 CC 4x4 non turbo. I was impressed it started tonight 16 degrees with wind chills of 6 degrees with out being plugged in

I let it warm up for 20 min before even trying to drive it. It was still cold in the cab (my teeth stopped chattering but still cold) It was a short drive Truck ran roughly 30 min. Still not any warmer. My gas vehicles are warm inside in 10-15 min after starting..

Another thing I noticed is that the blower isn't that powerful! Hi in my truck was like low-med in my van (04 GMC work van)

I searched through here and try to find a up grade for the blower motor. I think possibly bad T-stat?? I know to stick with Motorcraft or IH T-stat on replacement. not sure which temp to buy?

Any help would be great!

Thank you,
Michael

 

[madpogue]

A faster blower motor will just make it take LONGER to generate heat. If you had the heat running the whole time you were warming it up, you just prolonged it. Try running it 10-15 minutes with the HVAC controls OFF, then turn it to Floor heat, temp control all the way up, second lowest fan setting. If it still comes out cold, then you have an HVAC problem of some kind. Either the temp control door is not responding, or your heater core is clogged, something like that.

 

[mjs2011]

After the 20 minutes at idle, what was your coolant temp? I have a coolant gage on mine, and if it idles for 10-15 minutes when its 10 degrees out, Im lucky if the high idle even kicks off. Thats around 120 degrees. Not hot enough to produce substantial heat in the cab. Diesels make heat when they are driving, not while idling.

 

[Shadetreemechanic]

Sounds like you have a non Motorcraft IH thermostat. I have had that symptom now in several of these trucks and a good factory thermostat always fixes it.

 

[quickster]

You need a t-stat that has a high heat opening, 195 degrees if I'm not mistaken. I had the same problem on my diesel MB. Swapped the t-stat and now it cooks.

 

[sjwelds]

Just gonna throw this out because it recently happened with my truck. Now mine's a 92 so not sure of differences, if any. The heat/cool cable was frozen up. You could grab the heat knob and twist it a full circle and keep going if you so desired. Since the A/C hasn't worked since we bought the truck, I just disconnected the cable from the door behind the glovebox. Swung the little white lever that the cable had been connected to all the way to the passenger side, and voila....Full heat.

We've also blocked off a portion of the radiator in the past, with good results. Just find a chunk of cardboard the desired size and slip it down behind the grille.

Your method and results may vary

 

[icanfixall]

We only use the 192 degree factory thermostat. Anything else will fit but not function correctly. China is making a very close copy of our thermostats but they fail horribly. buy the stat from Ford or International only.

 

[mblaney]

Low tech way of diagnosing:

Run your truck.
Put hand on upper rad hose - is it hot?
Feel the smaller hoses running to and from your heater core - are they hot?
Is the temperature control knob on your dash stiff or springs back? Check your blend door - behind glove box.

If you have temperatures in your hoses that are 'too hot to handle' I bet you have a broken blend door; google this problem with any F series truck in our generation. I had to fix mine.

http://www.oilburners.net/forums/showthread.php?67077-heater-problem

I kind of forget how to do it but I do remember that the pivot was broken off. This thread has pictures that match the break that mine had.

http://www.ford-trucks.com/forums/857687-blend-door-fix.html

This is a really ****** job to have to do

 

[Rot Box]

Sherwin brought up a good point on the cable. Seized or not drop the glovebox door down all the way and slide the HOT_______COLD knob on the heater control all the way back and forth. Watch behind the glovebox and notice the white lever that's moving. Move that white lever by hand all the way to the hot position. Most brick nose trucks I've seen don't open all the way hot or cold which leaves you with a blend hot/cold setting. A couple times a year I have to move that by hand..

Check that and as others have said if you don't have a healthy Motorcraft t-stat you're probably going to freeze Good luck

 

[sjwelds]

^^ I've also read of stuff falling down the defrost vents and jamming the door so it wouldn't go all the way to hot.

Just giving the OP some things to check. this is good. this is good.

 

[BDCarrillo]

Older Fords liked to recirc only on max AC. If you don't have functional AC (or pull the plug on the compressor) pop it over to max AC and it should pull inside air and warm up faster.

I use a piece of wood in my fox body to prop the interior flap open, but it's more accessible.

 

[franklin2]

We've also blocked off a portion of the radiator in the past, with good results. Just find a chunk of cardboard the desired size and slip it down behind the grille.

Your method and results may vary

This is what I do with mine. I found a piece of 1/4" OSB, it slips right down in front of the radiator. I started with blocking 3/4 of the radiator, and ended up cutting it back to about 1/2 of the radiator. In the warmer weather I take it out and put it behind the seat. It works well, even when I am plowing with it.

 

[3Kp]

Thanks for all the replies. This weekend it suppose to get back up in the low 50, Of course there is 70% chance of rain

If I get done with work early enough on Saturday I'll check out the things you mention. I do know the fan switch is moody got to flip her just right to turn on. Not sure of it's deal but possibly figure it out to hopefully.

Really, Really wish I had a garage

 

[Dsl_Dog_Treat]

^^ I've also read of stuff falling down the defrost vents and jamming the door so it wouldn't go all the way to hot.

Just giving the OP some things to check. this is good. this is good.

The last heat problem I diagnosed and repaired for my buddy.

You must be registered for see images attach

 

[diesel458]

Kind of simple, but check your coolant level while cold. Make sure it's full. I had a radiator leak, and the coolant was low, when I kept it topped off, it heated up faster, and you could always plug it in.