johnr9q

I posted this yesterday in the 2nd generation no drive train and J body replied with a possible solution but it didn't turn out to be the problem so I have the passenger side torn up so was hoping. I have a 99 Ram Diesel and it has had this heater problem since I purchased it but now it is worse. I start the vehicle and turn the heater on and it blows cold (as it should) I then drive some distance and the temp gauge on the dash indicates the engine is warming up but the heater is still blowing total cold air. I then hear a click (Sounds like a damper is opening) and immediately hot air blows. Sometimes I can get the damper to open if I turn the heater temp control back and forth rapidly. When the truck was on warranty I had them look at this problem a number of times and they always told me this was normal. I do not live in a very cold climate (Sacramento) so it doesn't take a long time for the coolant to heat up but whatever tells that damper door to open is not doing it soon enough. It now takes about 15 minutes of driving on the freeway at 70 mph for the damper door to open and the temp gauge has indicated normal running temp for 10 minutes before it opens. When I go to a cold climate (Tahoe) the problem is much worse.

Stamey

Kinda sounds like the cable from the temp control is not working, but if it was a cable sticking you'd know it when you tried to turn the ****. My best guess is the cable is flexing near the temp control damper, or the **** end, and the damper is not moving freely. This could be caused by a foreign object(s) in the duct system, from leaves to a stick that somehow got in there.

Keep in ind this is all theory, based on your description.

*My* next steps would be to check the see that the cable moves, and that it is operating whatever it should at the other end. Next I'd be looking at the heater core circuit, to make sure the coolant is hot on the inlet and outlet of the heater core when this problem is happeneing, but you expect it to be warm. Do this at an idle, not driving down the road. You can speed heat up if necessary by chocking the wheels and putting it in drive or reverse. Make SURE the truck cannot move if you do this!!

Chris

johnr9q

I really don't think it is a mechanical problem, I think it is an electrical problem. Whatever provides the signal for the door to open when you start up your vehicle and initially it blows cold air like a/c then when the engine warms up and you hear a door open and then immediately the air coming out of the heater vents blows hot. Whereever the signal is generated from to tell that door to open is waiting way too long to send the signal. I now drive for miles with the engine warm in Sacramento mild climate before that signal is sent to change the air coming out of the heater vents from freezing cold immediately to very hot. The vehicle has had this problem since it was new but is much worse now.

Stamey

I know of no electical doors in that system. The only electrical thing in there, besides the blower motor, is the AC switch. All the doors are vacuum controlled. I wonder if it would warm up faster of you disabled the AC. You can do this by disconnecting the low pressure sensor in the filter-drier, easily.
Can you narrow down where you hear the click from?

Wracking the brain here,
Chris

neveragain

Yes it sounds like the control for the vacuum has had it. They are availiable at the auto wrecker at about half the price of new. I am on my second one. Or the line could be off but not as likely.

CattleKev

Johnr9q,

I have a '96 with a similar problem. I removed my temp. control panel to find that the hot/cold dial moves a cable that goes down to the top of the heater core plastic box. The cable then moves an arm that is connected to a door in the box near the heater core. On my truck the cable does not move the arm anymore and the door moves freely. To fix this one must remove the a/c and heater core connections, the dash and the entire HVAC plastic box that houses the heater core and a/c evaporator. I dont want to tackle this now so I fixed my heat issue with vise grips. I clamped vise grips on a shaft that is located at the bottom of the HVAC box (passengers feet area) and turned the shaft forward to the heat position. You can feel the heat/cold as you turn the shaft by hand. The vise grips are still clamped and shoved near the carpet for a temperary fix.
Hope this helps- Kevin

plow

Have you checked for oil in the vaccum lines?

J BODY

It's a 99 boys.....electric door actuator recieves signal from hvac control head to move the blend air door. I had him check the plastic "adapter" that is between the actuator and the blend door. That is the most common failure. I've installed enough of those to have one handy in my tool box (though usage has finally fallen off over the years). I've only replaced maybe two actuators themselves that were weak and wouldn't move the door, or the blower motor on high would actually push the door back the other way. Never seen a control head cause this. Not saying it couldn't, just hasn't happened in the cases I've seen. I've also not seen a blend air door break, but that is possible too.

Stamey

Hey J Body, your idea may explain why his kicks in down the road. It might be that weak adapter that finally moves the door. Wouldn't explain it if he left it in warm position overnight and it still did it in the morning though.

Chris

Barry Smith

J Body, what kind of a job is it to check the adapter? Mine will be blowing warm then all of a sudden it's blowing cold I turn the fan to "off" and back and most of the time it's blowing hot again?????? Any help is appreciated! About a month ago it was low on water but now its got plenty of water and still doing it?