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sherfield2002 11-07-2009 06:54 AM

Heater problem
I just bought a used 02 Ram and the heater isn't working like it should. When I first turn the fan on it will blow hot air for about 5 seconds then it cools off. If I turn the fan off for a few minutes and turn it back on, the same thing happens. The a/c works fine, just not the heater. Any ideas what might be the cause?

CHILLZ HEMI 11-07-2009 07:11 AM

That could be a few things...Coolant could be bad(or low level), air in the coolant system, bad thermostat, heater core...

sherfield2002 11-07-2009 07:14 AM

The engine does reach full operating temp, if that helps anything.

CHILLZ HEMI 11-07-2009 07:44 AM

Its still possible that the themostat is bad(in this case possibly stuck open), even though the truck reaches N.O.T. causing your case of just blowing the cold air...Check the hoses that run from the thermostat, and the heater core to see if they are hot or cold...They should be hot(or fairly warm anyway)...Now if your coolant is at the proper level in the RAD and reservoir(without any leaks from hoses, and the RAD), the thermostat is working properly and its still blowing cold air, check to see if you have a leak inside your truck or a strong smell of coolant coming through the vents, then thats a good indication of a bad heater core...

dodgeman70592 11-07-2009 08:29 AM

Good info right there ^^^

ya its a hemi03 11-07-2009 09:22 AM

yeah my dad was having the same problems with his 02 4.7 and replaced the thermostat and everything come to find out he needed his hoses flushed you could try that or even new hoses. that was all right around 80k to 85k miles

sherfield2002 11-07-2009 10:42 AM

The coolant looks good and I topped it off this morning, it was about .5-1in below the cold fill line. I'll crank it later and let it get up to temp and see if the hoses are warm later. I haven't noticed any leaks or coolant smell in the cab or from the vents.

erm 11-07-2009 10:56 AM

Do you hear the air diverter valve switching positions when you change from heat to defrost to bi-level?

If not, the little valve in your HVAC distribution box is sticking, the valve may be defective or there's a connection/electrical problem there.

That HVAC distribution box is under the dash.

sherfield2002 11-08-2009 09:41 PM

I think it may be the blend door. I know my mode 1 door is broken, air only blows from the vents no matter what the setting is. I suspect the blend door is broken too. I don't hear it change when i change from cool air to warm air, but i can get warm air briefly though so I'm not sure whats happening.

Toms Blue Ram 1500 11-08-2009 11:13 PM

Could be a blend air door issue or even a partially clogged heater core . Might try clamping off the heater hoses , removing them from the heater core , then take a garden hose with good pressure and flush the core with water back and forth between both nipples . Reinstall the hoses and see what that does for ya .

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