98 Silverado - No Heat

[Ateam311]

A few months back, the heat went out in my 98 Silverado and we had something replaced (I don't recall which part it was off hand) because it had shorted out (a module of sorts maybe?). Speed ahead to the present... my Silverado is once again only blowing cold air through the vents. However, if I leave the air off long enough and then turn it on, it'll briefly blow out a little bit of hot air.

 

Could it be that the control valve is stuck? Is there anything else I can check in the process of trying to figure out what the problem is?

 

Thanks!

 

- B.S.

[unit731]

With the old mechanical heating controls, it was easy. Just replace the thermostat.

 

Electric or electronic controls. Starts to get complicated. Hope others can chime in hear to help you.

[Big_D]

man i think all u need to do is backflush your heater core. i had the same problem in my 2000, cold air was blowing all the time but the engine temp was normal. i had a new thermostat installed when i did the water pump.

 

all you need to buy is a garden hose, some 5/8 heater hose like 2', and adapter to go from a garden hose end to a pipe fitting, then i used various pieces to get the heater hose attatched to the garden hose. as for your drain tube i used 6' of clear pvc hose. next, remove both heater hoses at the firewall. one should be hotter than the other(thats the one pumping antifreeze into the heater core) and the colder one is the return(probably blocked). slip your homemade heater/garden hose over the colder pipe, then tighten down with a hoseclamp. then clamp on the drain tube and turn on the hose...not too much pressure at first, let it flush for 5 mins, crank up the pressure. try switching hoses/alternate to make sure it flows both ways and its clear water.

 

try this out, should work good. did for me, was cold air all the time and now its like an oven.

[Ateam311]

man i think all u need to do is backflush your heater core. i had the same problem in my 2000, cold air was blowing all the time but the engine temp was normal. i had a new thermostat installed when i did the water pump.

 

all you need to buy is a garden hose, some 5/8 heater hose like 2', and adapter to go from a garden hose end to a pipe fitting, then i used various pieces to get the heater hose attatched to the garden hose. as for your drain tube i used 6' of clear pvc hose. next, remove both heater hoses at the firewall. one should be hotter than the other(thats the one pumping antifreeze into the heater core) and the colder one is the return(probably blocked). slip your homemade heater/garden hose over the colder pipe, then tighten down with a hoseclamp. then clamp on the drain tube and turn on the hose...not too much pressure at first, let it flush for 5 mins, crank up the pressure. try switching hoses/alternate to make sure it flows both ways and its clear water.

 

try this out, should work good. did for me, was cold air all the time and now its like an oven.

 

 

Awesome. Yeah, it can't be the thermostate. I'm pretty sure I replaced it not long ago plus the engine temps are normal. I'll definitely give this a shot when it warms up a bit.