Hi all, new to the forum & have a question; I have a 96 Ram with a/c & I'm not getting any heat. I can move the control to "recirculate" & it gets hotter than a pistol within 15-20 seconds, but any other setting it blows lukewarm air. I understand that the heater core may be plugged, but then why would it get hot so fast using the recirculate setting? Any info would be much appreciated!

 

Mine does much the same thing, just started this year, where on max AC (essentially recirc) it blows nice and warm, but on defrost or any other setting its barely lukewarm.

I'm going to pull my heater lines and try to see if the core is partially clogged or something, I'll let you know if I find anything. (Of course its going to have to wait until the wind chill here isnt -30 as it is this morning)

 

i'm confused.

on my 01 i have 3 *****, one selects a mode of heat/air, next is fan speed, and the last selects a temp. during summer i select one of the 3 AC settings and dial the the temp over to cold. (on these first three setting, i hear the compressor kick on). during cold weather i select one of the heat/defroster vent settings and dial the temp over to hot.

dillon, are you saying that one of the first 3 settings gives you a warmer temperature than the one's that have the single arrow at the top or bottom ? i just went out and did a test. my ac settings were not as warm as my heater settings...

 

Well first of all, your ac compressor should kick on in Defrost anyway. I've been told its done to dehumidify the air it blows on the window.

But yes, on the setting max AC, with the temp **** to hot, it blows warmer than any of my other settings.

This is what my controls look like:


The only thing I can figure, is that on max ac (which I believe recirculates) a slightly clogged core is able to warm up the air coming from the already warmer cab whereas the outside air being pulled in while on defrost or other settings is too cold for the core to warm up enough.

 

you're right compressor is on for each setting other than the 2 at about 1-2o'clock on the dial, the 2 with the single arrow at the head or foot.

i looked it up in my owner's manual and it does say that the max-ac is recirculate, whereas all other settings bring in fresh air from the cowl area.

this is a question - if the compressor is on, then the freon is expanding in the evap core in/around the heat box. wouldn't that take heat (and moisture) out of the passing air and make the resulting air cooler ?

 

Thanks for all of the replies peeps. I thought the same about recirculating air & being already warmer in the cab, but regardless, the air in the cab is freezing cold already & it only take like 15-20 seconds & it's blowing hot air. It has to be something else. Is there a duct or a vent that is spring or vacuum controlled that may be stuck open allowing the cold air in?

 

calling on all the experience out there.....

ok, i did another test, and FNG is right. when i'm riding around at normal engine temp and the heater on the "floor only" setting, i have lukewarm air coming out the floor vents. i switch the heater control to MAX-AC (which is recirc) and the temp control to hot, and i get toasty HOT air out the upper vents. this is great, except my feet are freezing.

can someone explain why this is and how it works.
where does the cold temp from the ac evap core go ?
is there any way to force recirculation to the floor vents instead of the uppers ?

 

Ok Let me give this a shot I bought my truck last summer it had sat for 4 years. I had poor heat from the defroster and floor vents in the winter. I went as far as unplugging my A/C Compressor, this helped but very little. As soon as it was warm enough to get in there and change my heater core I did and it has worked great ever since.

Now I'm one that just has to do as much as I can for myself because I don't trust anyone else and I can't afford them. I had hot hoses to and from my heater core and I knew my vent doors were working as I could hear them. I had no leakage without any smell of coolant of steam. But remember my truck sat for 4 years and was corroded so bad I couldn't believe the thing didn't blow up. just to give you an idea how bad it was the left rear freeze plug was half corroded completely through and it only had a slow drip.

bottom line if it were me I would be changing the core.

Chuck

 

I think my issue was an air bubble in the system. I popped the rad cap right after starting this morning to check coolant level (before I dug into the core) and it made a loud almost burping noise (lol). Anyway, my heater blew hot on defrost and all settings on the ensuing drive around the block. I probably didnt get the air out of the system all the way when I changed the pump, t-stat, and radiator earlier a month or two ago.

If it comes back I'm going to dig into the core, but for now it works.

 

I've got the same problem. We replaced the thermostat (THAT IS NOT WORK). We also got the radiator flushed at Jiffy Lube. (THAT WAS A WASTE OF MONEY)

We are thinking about back flushing the heater core.

Did you get your problem fixed?