Heater Performance Tip

[EvilSpirit]

A little tip from the frozen tundra of Southern Michigan. I've seen a few posts about poor heater performance, thermostat choices, etc. I was noticing poor heater performance, even though I was seeing engine temp and had good coolant flow through the heater core. Here's a tip - heater performance is tremendously better, especially during warm-up, by simply turning the heater function knob to the "recirculation" setting. It lets the heater start with cabin temp air instead of the usually much colder outside temp air drawn in thru the cowl - the heater core simply doesn't have to heat the air as far. Same in the summer with the A/C. While if the windows fog, you may have to toggle the function knob to the regular or defrost settings occasionally, but still the overall performance is greatly improved. And granted, being my truck is a 96, that the blend door may be out of adjustment or the seals may have deteriorated causing poor performance, but it's a lot easier to toggle the function knob occasionally instead of pulling the HVAC unit out. If you are having heat issues, it can't hurt to try. Willie

 

[rrb6699]

door seals are easy to replace. get some from a uPullIt yard. most times you can find good ones.
also I learned this one just yesterday. my alternator went. but, not knowing it was going bad, I noticed poor heater performance and not really bright headlights.

replace the alternator. a 30 minute job on these 2nd gens.

well worth it to have one that has proper output. now my heat is really hot because the fan works better. the truck seems to drive better and lights are brighter.

this one can catch you off guard. oh, carry an extra drive belt up north there.

 

[EvilSpirit]

door seals are easy to replace. get some from a uPullIt yard. most times you can find good ones.
also I learned this one just yesterday. my alternator went. but, not knowing it was going bad, I noticed poor heater performance and not really bright headlights.

replace the alternator. a 30 minute job on these 2nd gens.

well worth it to have one that has proper output. now my heat is really hot because the fan works better. the truck seems to drive better and lights are brighter.

this one can catch you off guard. oh, carry an extra drive belt up north there.

HUH? I'm fairly sure you have to pretty much pull the dash and heater box to change the blend door seals - about a full days job by most accounts. Even if it can be changed by just rolling the dash back, like the heater core trick, I'm sure that my unbroken '96 dash wouldn't survive being flexed like that. A lot of labor to fix something that works.

As to the alternator - not an issue. Gauge is just over 14 volts, lights are bright, fan speed is normal.​

 

[rrb6699]

I replaced all my door seals with nothing like the effort you say.

are we talking 96 1500 here?

 

[EvilSpirit]

Yes, I am referring to a 96 Ram.

You keep referring to the exterior door seals that seals the perimeter of the door to the cab door jambs. The exterior doors with the windows and mirrors that seal up the big holes in the side of the cab.

My post refers to the BLEND DOORS inside the heater box. When you rotate the heater control knob it switches vacuum to control servos that move BLEND DOORS inside the heater box to direct air to the proper area, direct air through or around the heater core, and chooses between drawing fresh air in from outside or recirculating cabin air. Sometimes the BLEND DOOR controls, servos, or vacuum lines fail or come out of adjustment. I'm not sure on the Rams, but many times the BLEND DOORS have seals that deteriorate or come loose and cause a poor seal. As I said - servicing the BLEND DOORS requires dash removal or at least strapping it out of the way, and probably removing the entire HVAC unit. I'm just speculating why my poor heater performance is corrected so well by simply setting the heater control to the recirc setting - possibly the BLEND DOOR isn't working 100%. At this point I figured out how to get all the heat I need just by proper control settings, and was trying to share this tip with the flock.