I finally got my 93 W250 running today 11/14, after killing the KDP and doing general maintanance (new water pump, radiator hoses). I installed a NAPA thermostat exactly how the FSM shows. After filling up with new antifreeze and running the rig for about 20 minutes locally, it seems like the t stat is not functioning properly. I am getting antifreeze to the upper radiator hose, so the t stat must be opening? However, when I was driving around, I didn't seem to be getting heat in the cab (with the blower on high, and the heat cranked up). I would get some heat for about a second, then nothing. I have a ball valve shut off on the input side of the heater hose, but that is in the on position. I am wondering if I got a junk t stat from NAPA. The radiator cap wasn't hot also? Any ideas???? I guess I will have to put up with it until I get a Cummins t stat The heater core was still working before I had my radiator out and back flushed - so, I don't think the heater core is bad. The blower motor might be going? I still think I got a bad t stat from NAPA!

 

if the motor is not overheating or not getting hot enough might be an air lock in your system. i just finished a second gen of my brothers that took a few times thru the heating cycle to get the heat to come up the defroster.. the other thing noticed is that it doesn't really draw the water into the rad. when cool. time for a new cap for me.

 

When you have an aftercooler you must open the petcock when filling to bleed air from system. Otherwise fill slowly to allow venting of engine coolant passages, and check level again after 2-3 minutes and top up if necessary.

 

I think you have a bubble too.

 

I found the problem. I had the vent hole on the t stadt at the 6 o'clock position, instead of the 12 o'clock. The thermostat is working fine now. I am getting heat in the cab. Not much, but the blower motor isn't pushing too much air out of the vents.
I believe the blower motor needs replacement, as well as the heater core? I know the heater core is a bear to install. I don't know how bad a blower motor install would be?

 

Check your swich before changing the heater core. I had a simaler problem and I changed the swich and it cured it . Just a idea.

Charliex25

 

I wouldn't mess with the heater core unless it's leaking.

 

Your heater plenum may be plugged up....

http://ramchargercentral.com/index.p...owtoshow;id=45

 

Ah c'mon Dave, a heater core job isn't that tough. It's well worth the little effort with the much nicer heat you gain. Get a new heater core from NAPA, much better heat IMO from 3 heater core jobs on these trucks. I'd use Cummins only t-stats though.

 

Thanks all for the help! I will replace the heater switch first, and see if that helps push more air. If not, I will probably look at the blower motor. Yeah, my heater core is most likely 13 yrs old, and should be replaced. I know it is a difficult job, from reading Dave's posting on the topic.
Anyone here ever install an in cab heater, such as the Mojave heater, or the one's West Marine carry. West Marine has an in cab heater from Heater Craft, with a rating of 40,000 btu. If your in cab heater every died, it would be a lot easier then taking off half the dash to get at the heater core. Just wondering if anyone here is running an in cab heater?

 

40,000 BTU!!!??!

Holy smokes, you could roast a honey glazed ham and all the fixin's right down on the floorboards! 5,000 to 7,000 btu's might be more like it for a truck cab. With 40,000 btu's you could drive buck naked in Antartica in a cold spell....

 

Jimmie,
Yeah, 40,000 BTU is one hot heater! The other Heater Craft model is rated at 25,000 btu's.
s. I believe the Mojave heater is 10 - 12,000 btu's.

 

Is the blower switch behind the heater/ac control panel? I am going to try replacing the switch first, then move on to the blower motor. Maybe replacing the blower switch will fix the anemic flow of air from the vents, with the blower set on high?

 

My heater/air conditioner wasn't putting out like it should either. I cut a window in the plenium right at the evaporator and pulled out half a quart of leaves, dirt, and dead bugs. I washed the coil with cool clean and made a replacement panel to close it out. I then took the vacuum cleaner and sucked out the drain hose on the fire wall and so far it is working great. Look in my gallery and find "New HVAC access"

 

"My heater/air conditioner wasn't putting out like it should either. I cut a window in the plenium right at the evaporator and pulled out half a quart of leaves, dirt, and dead bugs."

Boatnik,
Thanks for the input! I saw on a Ramcharger site, someone did the same thing. I am sure my HVAC system is plugged with crap as well.