1998(.5) And am 2500. Have a problem with AC/heat system. The fan works. The heat works barely and has since I got the truck 1.5 years ago. The pipes leading in to the heater core get very warm to the touch. The AC was working after the condenser was replaced a year ago, but then just stopped. I'm doing an extensive interior re-build so all the duct work and dash are removed and it still isn't working.

No coolant leak or smell in the cabin. All fluids are full. Haven't flushed the system yet, but am planning on it. I'm pulling the whole interior AC unit to clean everything and replace anything that I can figure out needs it. Any advice on diagnosing what the problem is and figuring out what all should be replaced while Ive got it all removed? Thanks for any help!

 

Possibilities:
Plugged heater core: I'm thinking internal blockage - if the external fins are debris-plugged, it would affect your airflow. I think the AC condenser comes before the heater core in the flow pattern (correct me if I'm wrong), so it catches debris first. Either way, you'd notice reduced air flow and you didn't report that.
Broken blend door (https://heatertreater.net/dodge-ram-95-02)
Failed blend door actuator (if your 98.5 has an actuator - this is cable-controlled on my '96)

Do you get better heat from the windshield defogger vents? If so, you may have a mode-door problem. You should also check the fresh-air/recirc door to see if it's properly working.

I believe there are some differences between the '98.5 and my '96, so I hope I don't send you down any false trails. (Insert numerous vociferous disclaimers here...)

 

@texasprd Thanks for the reply! The biggest problem I'm having is that I don't really know which parts are which. I have a Haynes manual, but it doesn't go into any detail. Ive tried finding YT videos on it, but cant find one that spells out what each part of the AC unit is and does. Any advice on where to learn about each component?

 

There's nothing like the factory service manual (FSM) - I sent you a PM with some info.