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Posted By: 89B150 89 Dodge B150 ac/ heater problems - October 28th 2020 12:40 am
I purchased this van not knowing a squirrel had chewed through the heater box near the fan housing.
They made nest in both inner fenders , I cleaned everything up , replaced heater core, replaced fan relay behind glove box.
Repaired the hole .
Now when I move the selector lever to A/C (left)the heater and defrost blow hot air from outside fan. If I move the lever to heat or defrost (right) the inside fan turns on and blows cold air.
This has been a frustrating endeavor. It seems to be backwards .
I could really use some Hvac diagrams my Haynes Manuel isn’t specific enough.
And the passenger side defrost doesn’t seem to blow very much . Could be a blockage?
Any help is appreciated.
No squirrels were harmed but they have prejudiced my views about them.
Posted By: Ram4ever Re: 89 Dodge B150 ac/ heater problems - November 27th 2020 10:58 am
I've been mulling this over. There's only one fan/blower. When you observe the 'inside' vents or defrost vents kick in, what's happening is that there are several vacuum actuated flap valves in the air plenum, selecting where the air from the one blower is routed. That vacuum actuation requires lots of tiny rigid hoses. One of them drives the fresh air/reirculate flapper door in the air box. I'm wondering if the squirrels chewed through it? That would defeat the reirculate door.

Are you aware of tte multifunction purpose of several of the pushbuttons in the climate control? If you push them in, then manually pull them back out, it commands the flapper valve in the air plenum to route the air out the dash vents. That's great for moving huge amounts of air.

On top of the air box where the cable attaches to the hot/cold lever, there's a peculiar self adjusting clip. If it were installed with the lever in the incorrect initial position, you might experience poor function. I'm not sure you could get it completely reversed, but between the fresh/recur ulate flapper and the heat/cold door, there may be considerable interaction.

I have to agree with your thought that there may be clogging of tte air plenum to cause the imbalance in the defrost. Probably some squirrel nest.
Posted By: 89B150 Re: 89 Dodge B150 ac/ heater problems - July 04th 2022 4:23 pm
I don’t have push buttons, it’s all levers , I have given up fixing factory A/C , I fixed the heater by replacing heater core and some flex tape . thank you for your reply. My current problem is removing the smog pump.
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