OffRoad
1/2 ton status
when my truck is in motion, the heat blows out like normal, then when i stop, it starts blowing cold air, not good.
any idea why this would be?
any idea why this would be?
CK5
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Heat cuts out at stoplights, why?
- Thread starter OffRoad
- Start date
1st thing I would do is check the coolant level. If it is ok, your blend door is probably vac accuated, dont know what truck it is, and you have a vacuum leak somewhere in your Heat-AC door system under the dash. Hook up a vacuum gauge and see if the heat changes with change in vacuum.
85-m1028
1/2 ton status
I just had a similar problem, turns out the fan clutch was bad and the fan was locked up...
OffRoad
1/2 ton status
it's a 90 chev 1/2 ton.
shaun89
1/2 ton status
i was thinking vacum too...but isnt the temp just manual doors, and the direction of the air is vacum? my vacum is alllll destroyed (the one thing i hate about "silverado" version) and i can control the temp by just moving the lever, i think it just turns a door manually with the lever....but other then checking the coolant level...i dont no...
I was thinking vacuum controls initially as well, but that doesn't make any sense. Cruise or idle, the vacuum is going to be high, acceleration it will be low...
On a '90 truck the heater controls are either electronic (with A/C) or cable (no A/C). Most likely low coolant or restricted heater core.
OffRoad
1/2 ton status
i don't have a/c. its a very base truck. i think i can feel the cable moving.
you guys know a lot.
you guys know a lot.
Did they go to a shutoff valve y any chance on the heater core lines on those?
First thing to check is coolant level, as stated above. Then look for a valve on the heater core hose under the hood. There may be something going wrong with the controls for that. It could probably be bypassed, at least for the winter. Cutting coolant to the heater core is only a small improvement in the summer anyway.
It's possible that there is a restriction somewhere and the water pump is only flowing enough through the core when the engine speed is up. Maybe it just needs to be flushed?
It's possible that there is a restriction somewhere and the water pump is only flowing enough through the core when the engine speed is up. Maybe it just needs to be flushed?
85-m1028
1/2 ton status
do you have a coolant temp gauge? if so is the coolant getting up to proper temp range?
dick_landy
Registered Member
i had the same problem, turned out it was low coolant. i was losing it from the over flow tank. there was a small crack where the rubber hose attaches to it. every time i would get stuck mudding, the rad would fill the over flow tank and then leak out instead of staying in the system.
mudboggink5
1/2 ton status
sounds like low coolant to me.
