the_merv

iTrader: (86)

I'm posting this up hoping someone else has the same problem..I've checked the basics.

Truck is a '99 Sierra SLE 5.3, it has the Full Center Console.

The Heat doesn't work if it's extremely cold..as in right now it's in the 20's. Truck is fully warmed up running at 200*. If you turn the Blower to 1 it blows faint Heat, any higher and the air is stronger, just colder. I pulled the lower Dash off and checked the Hot/Cold Door & Module, it's working fine..moves one end to the other. Both Heater Hoses under the Hood are hot, so the Heater Core is circulating hot coolant from what I can tell.

It worked fine till one day I got on a road that was bumpy as fck..hit a big bump and since then it's been dwindling out.

I'm about to pull the lower Dash apart and get in there to take a look..figured I'd ask before I tore into it and it be something simple.

LS1MCSS

iTrader: (18)

Sounds like you have an obstruction somewhere. Time to tear into the lower dash to see what's going on.

the_merv

iTrader: (86)

Ya that's goin to be interesting if it comes to that..gonna need a 6 pack..

SincalT/A

iTrader: (16)

Make it a 12...It will be easier to walk away and sleep tonight if you dont fix it or break more ****.IME

budhayes3

iTrader: (19)

Maybe the hot/cold door is broken...the actuator may be moving but not moving anything...

Gadgetized

iTrader: (9)

I would also check this. Did anyone ever run any radiator leak fix stuff like barsleaks? Before I tore too far into the dash I would unhook the heater core lines and flush the heater core real good.

the_merv

iTrader: (86)

I looked at that and the Rod it moving, and I can hear the door moving in the ducting.

I've been thinking that..I looked into the overflow and there appears to be that brown **** from one of them stop-leak pellets..

I've had the truck for almost 4 years and this is the first time it's done it..time for a good high-pressure flush I guess. I was planning on doing it and switching over to the green stuff when I did my Cam Swap.

the_merv

iTrader: (86)

So I get to work..one heater line hot, the other cold..maybe lukewarm at most.
Truck was 200*.
A flush is in order..