Heater

[glathrop]

Any one i changed my battery cables unhooking the negitive
first. Rehooked negitive last. Now heater runs hot only no matter
where control is. Worked fine before.

[Chris Stewart]

Which year Bravada?

[glathrop]

1998

[Chris Stewart]

The heater temperature is controlled by a door between the cold & hot air sources and operated with an electric motor. Sometimes electric devices get "lost" and can be brought back by disconnecting then reconnecting the battery. Since that's what evidently set off yours, you might try turning the temperature knob to cold, turn your keyswitch on then slowly turn the temperature knob to hot. That's how you reset the throttle position sensor on a '98.5 to 2003 Dodge Diesel and both control devices are potentiometers so maybe it'll work on your heater controls. You might try similiar exercises with disconnecting then reconnecting the negative battery cables too.
You might also check the heat&ac fuse too.
Let us know as this is the first one of those I've read about.

[BrownBravada]

I was just wondering if you solved this problem because my 98 does the exact same thing and now i can get heat but no A/C.

[jharris26]

i am having issues with my heater. i get good a/c but no heat. i tried the resetting(turning from cold to hot slowly). haven't tried unhooking the battery yet. i don't think its the heater core, cause i flushed it last year and had great heat till spring. on odd thing is that if i turn off the fan and turn it on real low, i get some heat (not much at all). and when i turn up the fan, it turns cold. any ideas?

[Chris Stewart]

There's a hot air source/cold air source blend door and it's driven by a little electric motor...instead of a simple cable slider like the older cars...
Other posts describe the little motor behind the glovebox on top of the plastic air handling box assembly.
I'm wondering if turning the temperature knob to cold then turning the keyswitch ON THEN turn the keyswitch off, turning the temperature knob to hot THEN turn the keyswitch ON would get the blend door to free itself.

[glathrop]

Originally Posted by Chris Stewart

There's a hot air source/cold air source blend door and it's driven by a little electric motor...instead of a simple cable slider like the older cars...
Other posts describe the little motor behind the glovebox on top of the plastic air handling box assembly.
I'm wondering if turning the temperature knob to cold then turning the keyswitch ON THEN turn the keyswitch off, turning the temperature knob to hot THEN turn the keyswitch ON would get the blend door to free itself.

In my case i opened up the little motor and a gear inside was broken

[jharris26]

99 bravada

i got the glove compartment out and i see a motor that controls the direction of the air flow (a bar attached to a motor on the left of the glovebox). it moves fine on its own. there is another door that i can push open manually on the right, but that just seems to be the door for pulling air in from the cab. i am still confused why the a/c would turn itself on when i have the heat all the way up. as far as the fluid flow in to the heater core, one side is hot and one side isn't. would that indicate a blockage in the heater core? is it possible to flush the heater core without dumping all the fluid from the radiator?
josh

[Chris Stewart]

HI Josh,
The hot line/cold line sounds like a blocked heater core to me too. You can siphon all the coolant out of the radiator with a small line into a jug or bucket, take both heater lines loose from the ENGINE, hold a garden hose to one line and let some water under low pressure into it. The other line should be placed so water can get out without wetting everything under the hood and drain into a pan for recycling.. After flushing one direction until it runs clear, flush the other hose, still keeping the outflow in mind, until it runs clear. Reconnect your heater hoses to the correct ENGINE connections, refill your coolant into the radiator, top off the radiator with new coolant then give it a try.
The reason to leave the heater hose/heater core connections alone is to not disturb the heater core or it's tubing to avoid a heater core leak and replacement....don't pull on the hoses or allow the pressure to build up with your garden hose connected. Do not connect the garden hose to the heater hose with a hose clamp, hold it manually for a few seconds and observe the outflow from the other line. If the outflow stops for any reason, disconnect the garden hose from your heater hose and make sure outflow from your garden hose is still present then resume.

[jharris26]

thx for the response, i did get it flushed. put in a flushing solution, ran that through, reflushed, and filled it up. i have heat now. after reading your comments on the pressure with the heater core, i hope i didn't put too much pressure. the only thing i still can't figure out is why the a/c will come on when i put to auto on the climate control. some are saying that it might have to do with getting the humidity out of the air. any thoughts?

also, i totally agree with your thoughts on the stupid heater blowers access, that would stink to have to get to that.

[Chris Stewart]

The ac coming on while on auto? Ok, lets suppose you're riding on the interstate, just waxed the car & lookin' cool then you get off to get a burger. Your auto was set for holding a certain temp and while you're cruisin', the motor temp is stable and you're losing a certain amount of heat through the body vent system. At the redlight, the heat of the engine builds because at idle, the water pump isn't spinning as fast so the coolant temperature through the heater core is higher and because the body vent isn't affected by wind, not as much heat is escaping the car. The sum of all this is the inside of the car heats up fast so the ac comes on to cool it off.

[BrownBravada]

My 98 gets heat no matter what temp either. When my battery was disconected the same thing happened so i doubt that it is the motor. Just wondering if the other guy figured it out on how to reset

[Chris Stewart]

BB, how do you know the blend door isn't stuck in the hot direction?