October 18, 2009My heater has started blowing cold air and not heating up like it should. I put a new thermostat and flushed the cooling system with no results. A little heat creeps out at an idle, but when I start driving, the air is a lot cooler. Anyone have any thoughts?
Forums : Silverado (c/k) (1999 - 2006) : Heater blowing cold air (3237 Views)
October 18, 2009Did you check the coolant reservoir and radiator again to make sure it has enough. It may take a few times adding coolant to it after you do a flush and refill to get all of the air out of the system and the coolant to stay at the proper level.
October 19, 2009Check the heater blend door actuator and the heater control valve. Both are possibilites.
October 19, 2009have you recently replaced the radio? on my 98 a bare wire touched the back of the HVAC control unit when the radio was being changed and it fried the control unit
October 19, 2009Have not replaced radio or any other components. Thanks for the responses, I`ll look into them.
October 20, 2009theres so many things it could be heater core...or blend doors or blend door actuator or even bad controls...it might be worth it to let someone diagnose it to know for sure before attempting to replace stuff cause most is complicated
October 20, 2009Heating and AC systems without the automatic digital control boxes are pretty easy to troubleshoot. I have helped several of my neighbors with theirs even on some Fords. Their all basically the same. To check the flapper door just change your selector from floor to vent to defrost if the air changes that is all good. change your temperature settings and check the difference in temps. If it doesn`t get really hot at normal operating temp there is a problem. First check your coolant level if it is good you said you already changes your thermostat. One concern with that is it isn`t upside down in the housing. Most won`t do that no more because they will only fit one way on many vehicles now. If your coolant is good and your confident on your thermostat, put your hands on the heater hoses and feel the hoses to see if they are the same temperature as the radiator hoses with the heat at full hot. If they are quite different then you have a heater core or valve problem. After you check these things post back up your findings.
October 20, 2009Try purging the system. I`d bet you`ve got air trapped in the heater core.
Basically, you take the cap off of the reservoir, put the heat on full blast, start the truck, and let it idle until the t-stat opens. Then rev it up to 3k, and hold for a few (5-10) seconds, then let it drop back down to idle for a few seconds. Do this until it reaches operating temperature, and shut the truck off and let it cool. Check your coolant level, it may have dropped if you got any air out of the middle of the system anywhere. Replace any lost coolant, put the cap back on the reservoir, and go for a drive to check for heat.
October 21, 2009I would say the actuator is bad I had that problem with my 04 2 times and trust me is a pain on the to change it
October 21, 2009Tried purging the system today and it seemed to work pretty well. I didn`t have to add any additional fluid though. I`ll double check it in the morning and if that`s not it, I`ll try another suggestion. My actuator and mixer seem to be working fine, so I`ve got my fingers crossed that it won`t be the heater core. I probably won`t see any real cold weather for a while being in south Alabama, but I want to be ready when I need the heat and defroster for the chilly,frosty mornings
October 23, 2009I haven`t logged on to the site for a while and did today to post this same thing. I started my truck in the morning a few days ago and it ran for 15 minutes, forgot about it, but when i got in the inside of the truck was still freezing cold. I looked at the temp guage and it was already at operating temps. I`ll try to do some trouble shooting tonight when i get home. My truck is an 06 and i hope there is not a heater core problem.
November 23, 2009Finally fixed my heater problem by backflushing my heater core by using a link I found: http://www.olypen.com/craigh/heater.htm. Be careful with the quick connect fittings that are on the heater core inlet and outlet lines. they become very brittle and it didn`t take much effort to break the nipples off inside the hoses. I found the fittings at O`Reilly`s. The part #`s are Dorman Quick Disconnect #800-409 and the tool to take them off is # 800-450. A regular quick connect tool will not work because either the sleve that fits inside the fitting is not long enough or it is too thick to fit, you have to have the tool that are made for these fittings.
My heater works great now, better than it has in a long time!!