Mechanics

CHEVY 4.8-2WD HEAT PROBLEM

2000 Chevrolet Silverado • V8 Automatic • 2,000,000 miles

2000 Chevy Silverado 4.8 2WD, No heat. This last fall I had a problem with the heat and air, I either had great heat or great air, not in the same day. If I picked one in the it stayed for the day until overnight then I could choose again. The truck temp. Is normal. The hoses going into the firewall - one is very hot at idle the other cold. I was told it wasn't the thermostat but the lower actuator door that must be stuck because that is the one that deals with the heat. I have replaced that and could feel the motor moving the door but still only get great air and trickle slight warm air. Its 30 below and I need heat and help. Thank you.
Avatar
Tasocd65
December 12, 2010.



Start engine and check if its reaching operating temp
if not you need a thermostat
if it is reaching operating temp
open hood and check heater hoses under the hood if both hot
need to scan for codes
Determine if HVAC, Body Control Module, or Powertrain Control Module DTCs which may affect HVAC operation are present.
The presence of DTCs which begin with "U" indicate some other module is not communicating.

Let me know

BMRFIXIT
Dec 13, 2010.
It does reach operating temp. And only one of the hoses is hot the other cold. How do I scan for codes?

Tiny
Tasocd65
Dec 13, 2010.
Need a scan tool to get to the codes

While engine is warming, VCM monitors ECT sensor to determine the amount of time it takes engine to reach coolant temperature required for closed loop operation. DTC P0125 will set if VCM determines that ECT does not reach minimum coolant temperature required for closed loop operation in a specified amount of time.
Scan tool displays engine temperature in degrees centigrade. After engine is started, temperature should steadily rise, and then stabilize when thermostat opens
if not thermostat should be changed

reading INFO about heater oper: The temperature of the air coming from the heater duct and the defroster nozzle is regulated by controlling the relative amounts of warm and cool air coming from the heater module. The temperature valve determines the amount of the total airflow that passes through the heater core.
When the temperature **** in the control assembly is at the extreme left side of travel, the full BLUE, or cold position, the temperature valve stops all the airflow through the heater core. The heater duct and the defroster nozzle receive only unheated air.
When the temperature **** moves away from the full BLUE, or cold position, the temperature valve opens to allow an increasing amount of air to pass through the heater core. At the same time, the temperature valve reduces the amount of unheated air that enters into the mixture. The result is a very responsive control of the temperature of the air discharged through the heater ducts and the defroster nozzle.
When the temperature **** reaches the full RED, or hot position, to the extreme right end of travel, the temperature valve diverts all the airflow through the heater core for maximum heating.
Hot coolant from the engine moves through the heater core and returns to the cooling system when the engine is running.
The heater system provides heating, ram air, power ventilation, and the windshield defrosting. The blower fan draws outside air from the plenum at the base of the windshield into the heater module. The forward movement of the vehicle forces additional outside air, or ram air, into the heater module. Within the heater module, the air is heated. The heated air is routed through the ducts to the proper outlets for discharge into the passenger compartment. A control assembly in the instrument panel allows the operator to control the blower speed, the mode of operation, and the temperature of the air coming from the heater system.
The heater module contains components that heat the air, and direct the air to the proper ducts and outlets.

BMRFIXIT
Dec 13, 2010.
So.I understand how the gauge works and where the air, whether cold or warm comes from, without taking it to a garage I was hopeful of fixing it myself. If the one hose is hot and the other is still cold when I have the engine running and the max heat setting, the engine is not overheating so it seems the thermostat is working. Could it be the top acuator door, or the heater core is blocked.I just to flush the system? I understand the codes and how it would help but the auto store code reader only works if theres a engine light. With very limited funds I was trying to avoid just taking it in, I appreciate your help, I hope you understand my position.

Tiny
Tasocd65
Dec 13, 2010.
You can buy an inexpensive infrared temp reader like I did and nenevr have to wonder about temps again!

Tiny
Fixitmr
Dec 13, 2010.
Sorry
let me try to be short this time
since you don't have enough coolant going through the heater core, your not going to have heat inside

you need to isolate heater core and flush
one way out the other and vise versa
until you have good flow on both direction

let me know

BMRFIXIT
Dec 13, 2010.
2 million miles huh? I'd say the heater core might be plugged! Back flush it and see what happens!

Tiny
Fixitmr
Dec 13, 2010.
Is this part of a flushing special they do in a shop, or does this require more attention. Would I have to do this on my own, taking off the hoses at the fire wall and flushing this way or would they do this if I took it in.I appreciate your help, and i'm sure you all, realize the typing error (200,000).

Tiny
Tasocd65
Dec 13, 2010.
IT CAN BE DONE AT HOME
I WOULD SUGGEST REMOVING THE HOSES FROM THE OTHER END AND NOT AT THE FIREWALL AS THAT WILL ELIMINATE THE CHANCE OF BRAKING THE HEATER CORE
FLUSH THAT WAY
LET ME KNOW

BMRFIXIT
Dec 13, 2010.