Hey all- been a while since I posted here... just haven't had any issues with the truck in FOREVER.

Got a couple minor ones all of a sudden, though.

it's a 99.5 F250 7.3....

Couple months ago, the HVAC blower motor started only blowing on settings 3 and 4... So only fast and faster speeds, no low or medium. Not a big deal, so I didn't think much of it.

I assume this is due to a dead resistor pack? Would that cause only two settings to work, or is it usually all or nothing? Should I suspect the dash switch because two work? Or it is a dual stage pack or something?

Also- two weeks ago (last I drove the truck) heater worked fine. A/C works fine. Go to drive home tonight and heat did not work. KINDA worked after 20 minutes, but only luke warm. Truck gets up to temp fine, no change in heat output between idle/moving so I don't suspect the thermostat or water pump.

I have plenty of coolant. Heater hoses going to firewall show something interesting- hose that goes from block to firewall is hot, hose from firewall to water pump is not very hot at all.

Is there a valve inside the heater core? If not, I'm pretty sure it's plugged. It's been kinda smelly since I got the truck, but ONLY on heat, and not on A/C. But it's not leaking as far as I can tell, and I have looked pretty closely at it to make sure.

I suspected the blend door at first, but since the one hose is not hot, what do you guys think? Plugged? Or is it normal for that hose to be significantly cooler because it's the return? I doubt it, but you never know....

Thanks for any help.

 

Here some good info if you have to remove the heater core.. see Post #5
https://www.ford-trucks.com/forums/4...ntifreeze.html

 

Thanks. Already found that link, but now I can't lose it because it's in my thread.

I'm hoping it won't have to come down to taking it out, but if it does, it looks like I'm covered...

 

Does it have the vac valve to shut off the flow through the heater core ? Just thinking maybe vac leak there. If not I'd take the hoses off & try to blow it out, wouldn't use a whole lot of pressure maybe 15-20lbs

 

I had the same problem. Mine was a blown head. Loosen the res cap and see how much pressure is built up, should not be much at all. The cap is regulated for 16psi.

 

Definitely replace resistor switch for blower problem. May have a bad heater valve or as was said before a pluged heater core. Check hose temp before and after heter valve.

 

It's not a blown head... I didn't drive the thing for a month and all of a sudden the heater does not work. Runs normally otherwise. I'd think SOMETHING would have changed if the head went bad.

As far as a valve being concerned- IS there even a valve? Like, did all these trucks have a vacuum valve inside the firewall?

I was under the impression that there was no shutoff at all, and that's why guys installed the ranger valve in the engine bay to get colder A/C.....

Seeing as how one line is hot and the other is cold, it point strongly to a clogged core.... I'm just trying to get a better idea of what to look for before I jump in there...

 

If one hose is hot and the other is cold, the core is clogged.
Hardest part about doing that job is disconnecting the quick connects at the firewall.

 

Sweet. Exactly what I needed to know. Didn't want to get in there and find out there was some kind of crazy valve setup.

Yeah, I was REALLY pleased to find out I didn't need to pull the whole dash out, so this should be cake.



Thanks, man.

 

The heater core is probably clogged causing the heat issue,but as far as the blower goes,used to mine wouldnt start up on low,i got out and tapped on the blower motor a few times and its worked since.It would be worth a try.

 

Here's a how-to, with pics, on disconnecting the heater core hoses. LINK

 

Thanks for the link, Robin- i found it earlier, but it did me no good. They would just not come off. Seemed like one side would clip loose and then the other side would get jammed up.

I was 90% sure it was the heater core, so I just cut the tubes off at the firewall. The quick connect fittings were still a pain to get off at that point, had to pry one side of the clip off with a screwdriver on both of them.

Anyways, turns out the heater core was indeed plugged. I managed to clear it out after a couple minutes with the garden hose, but there was evidence that it had leaked at some point, and I had cut the ends off of it, so I just replaced it.

Truck blows hot after about 5-8 minutes of idle now, before the gauge even hits the first line. MUCH better.

Also, the resistor is what was causing the blower issues. Pulled it out and looked at it, and just moving it around caused the blower to only work on the highest setting, when before I touched it, I had two settings....

Nobody has it in stock, but it's easy to get to and I can get it cheaper online.

Thanks again everyone!!

 

Glad you got the new core in and the resistor is available online. As long as you have at least one fan speed you can keep warm.

If you can post a part # and site for the resistor it would be good for the rest of us just in case.

Since you think the core once had a leak maybe a PO used stop leak and that finally accumulated into a clot in the core. Like plaque in an artery.