Not a Rat,but

[CR55]

I know this question has nothing to do with Rats, but I need some help. I have a 2006 Chrysler mini van that has a heat problem. The heat coming out goes from cool to hot and back to cool as you're driving. The faster you go the hotter the air, but when you slow down the heater starts blowing cooler air. Any ideas?[S (Unfortunately I can't drive 80 mph all the time!)....CR

 

[Shea Laking]

How's the coolant level? Does it ever drop? If you have to add coolant, you may have an internal coolant leak, like a head gasket.

On the more promising side, have you ever done a thermostat? They're generally not that expensive and are usually easy to change-would be a good place to start, the spring weakens and they do wear out over time.

Hot, cold, hot, cold could also indicate air pockets in the cooling system somewhere which may incate some sort of external coolant leak as well. I believe the coolant tubes for the rear heater run underneath the body, which leaves them at the mercy of road debris and the elements (aka SALT, ugh!)

Dunno if any of this rambling will be of any help, but at least this will give you a couple of places to start looking over the next day or two. The "Christmas Crawl" to visit family and friends will be no fun without heat!

Best of luck.

Regards,
Shea

 

[hotrod preacher]

i sure hope someone can tell ya.......b/c my wifey's 2004 is doing the same thing--just not as much...usually the heater will not blow warm unless going up the road..[S

i had decided the heat/air "box" under the dash might have a vaccuum leak--then i was "informed" that it was unlikely that any of it was vaccuum controlled......

so anyway there's another possibility-and i sure hope someone else can offer some advice

 

[Gasser300]

my sons 93 Chev did that. Was a plugged up heater hose/port at the intake manifold.

Betcha thats it

 

[R Pope]

Pretty much any heater after about 1985 is vacuum controlled. Some have a canister with a check valve to retain vacuum, and the valve fails. I have a Dodge pickup that has a leak somewhere under the dash, and the heat is sporadic. Can't find the leak.

 

[Shea Laking]

Good replies! I hadn't even thought of a vacuum leak! I'm not sure about the Caravans, but I do know that the full-size Ram vans had vacuum (fixed a couple with the same problem when I worked for Ryder).

Hope you can get 'er fixed, CR55! Good luck I'm pulling for you!

Regards,
Shea

 

[440Clark]

Gasser300 might be on to something. I would touch the two heater supply hoses with engine at op. temp. They should be close with supply being slightly hotter than return. If return is cold, there is an obstruction in flow, heater core, supply port as mentioned by Gasser300, kinked line, control valve. If heat is close on both sides, suspect bad thermostat or blend door ain't working right (goes back to vacuum leak, blend door actuator issues)
Good Luck! Keep us informed.

 

[Gasser300]

rusty crud had clogged up a heater hose and when on the gas it would force enough water through the core, but at idle wouldnt and the air would turn cold.

 

[CR55]

Let me throw some more B/S into this problem! It blows very hot air when you are going at least 40mph minimum. Any speed under 40 and it blows cool air! I'll check the 2 hoses when the van comes home (Christmas shopping), that sounds like a good place to start. No coolant leaks ever. I'm completely confused![S..........Thanks for all the help though. I really appreciate it. This is why I love this site.[cl

 

[rockabillyrat]

ok you have heat when you are driving over 40mpr becasue the water pump is spining faster and is moving the coolant into the heater core. first of all the blend doors are all electric on this car. they dont use vacuum switches any more. next if it was a problem with the blend doors it would not come and go you would have heat or no heat thats it. third its not a pluged heater core. never seen one on a caravan but the heat would do what you are saying check the heat hose temps like 44clark said. i bet you have a leak. even if you dont see one it still might be there. you need to pressurise the system and check for the leak. check the water pump i do alot of them on these cars. also the metal transfer pipe on the bottom of the water pump likes to rust out and leak. also do you have rear heat. if so check the rear heater lines. they rust out and leak alot. if not leaks then you may have a head gasket problem. but i have never seen on go on a caravan. the 3.3 and 3.8 are good engines. if you need any help let me know i work on these things every day.