I have a 98 dodge ram 1500 5.9L. I only have defrost and it blows warm at best... gets colder as I drive it. I flushed the entire system, replaced thermostat. No help. Both the heater hoses are warm/hot to the touch. Blower is strong. Temp gauge sits at around 170 tops. I put cardboard over the radiator and it went up to around 185. I can hear the thump of the damper going from heat to ac. I took off the glove box and looked for damper issues. Without knowing what i'm looking for, I can't tell what to do. I flipped the recirc door up to see the top of the blower motor. I did not see any thing blocking it. Thoughts? It's frigging cold up here in Ohio.

 

There was just a thread on burping the coolant system, you might have an air bubble. What temp tstat did you put in? You may have a vacuum leak causing the defrost only.

 

Definitely look for any vacuum leaks since the vent positions are vacuum controlled.

 

I'm not sure if you and I had the same problem, but on my recirc door actuator, the rubber boot inside melted and caused a lot of problems in my vents. The major problem was it blowing air out the defrost vents under acceleration. Followed by it popping and coming back out the front vents. One thing I know about this vent system is if one thing is off, it throws everything off.

 

That's always a vacuum leak, and almost always a vacuum check valve. The OP doesn't have that problem.

 

Well there goes my one good deed for the day...

 

I've got to say, as I should have already, that it's a good catch on your part to have found a leak that's wasn't one of those check valves. And also that I may have misspoke... While the OP may also have a vacuum problem behind the vent door operation (selecting floor, dash, or defrost), the temperature is controlled by way of the cable actuated blend door so vacuum's not involved in that.

The only things really involved in heater temperature control once you've got hot coolant reaching the pipes that poke out of the firewall are the cowl air intake (which can become obstructed with leaves, snow, pedestrian corpses, and such), the blend door, and the heater core. It's not unheard of for blend doors to break south of the actuator, but if the air is in fact being directed through the heater core and is still reaching the cabin cold, that pretty much narrows it down to either too much air within the heater core or too little landfill around it.

 

Thanks... i'll ck for vacuum leaks especially around the check valve

 

No problem UnregisteredUser, I only jest