I have an 02 Ram 4x4 SLT with about 65k niles on it.
When the truck is warmed up I have NO heat. When you 1st turn the heat on it blows some luke warm air for about 30-45 seconds and then stats blowing cold air. It does not matter if you are at an idle or up to speed on the highway. when the truck warms up I can grab both hoses going to/from the heater core and both are hot. Does anyone have any ideas on what I can look for?

Thanks Tony

 

I had a heater core go bad once but it was warm going in and cold out showing the core was plugged. I wondering if there maybe something plugged in the engine. I think it should be warm at least on one side going into the core.

 

Have you looked at your thermostat? You may have one that is going out....

 

Possible stuck t-stat, or perhaps no air is being blown over the coils (fresh outside air only). What does the temp gauge read?

 

Temp gauge is normal it stays pretty close to half way seeing how it has a dummy gauge in it I don't know the exact temp but stays the same place as my other 02 Ram.

 

Your blend door is more than likely stuck.

 

Could be that your t-stat might be stuck open a little bit. I had this with one of my other vehicles, it blew out warm air (not real warm either). Your temp. guage can still go up slightly but not getting the proper heat. I replaced the t-stat and now you have to keep turning the temp. down, it gets to hot.

Could also be a line clogged or low coolant level will also cause your vehicle to blow cold air and have a temp. guage in the normal range.

 

It seems we are not alone in this. I have an 01 ram with 93K plus. It has been blowing warm air since i got it used at 24K. If you speed up the RPM it gets warmer, at idle it drops 20/30 degrees or more. Once in a while it works fine. This leads me to believe it's not the thermostat which has been replaced twice. I'm not a mechanic but I don't know what the water pump could have to do with it. I have not tried the Rad. cap yet, but that may be soon. Other than warm air instead of hot everything on the truck seems to be fine. I did have it at the dealers several years ago for a steering piece recall and while there I mentioned to the scheduler about the problem with the heat. He got the mechanic to come out and I explained the problem. He said he knew what it was and could easily fix it, which he did. Don't know what he did but he said it had something to do with the vacuum and some mixing valve-switch-door or something like that. I got the impression it a vacuum connection or hose problem. They didn't charge me anything for fixing it so it couldn't have been much. Now, the rest of the story...that lasted about one year. Now it is back to warm air again and I don't know where to look or exactly what to look for.