My Truck Is Trying To Freeze Me Out

[oldscsc]

-- 2001 Silverado 1500 --

 

My truck only blows warm air (about 70F). It's running where it should coolant temp-wise. It will blow hot once in a while. This makes me suspect the blend door actuator.

 

Assuming my heater core is good and unclogged (because it blows hot once in a while) that leaves the HVAC module and the blend door / actuator. I'm assuming the actuator is a more common problem than the module giving out.

 

Sound like the problem is narrowed down? Also, which one do I need (upper or lower)?

 

http://www.oreillyauto.com/site/c/search/H...d+door+actuator

[502ci]

You have ruled out your thermostat already? If not that would be the first thing I would check, it could be stuck open and only closes once in a while that's when you would feel the heat.

[oldscsc]

I just replaced the thermostat a month ago because the truck wouldn't warm up in anything under 50F. That problem is fixed and now the truck runs at the 205F it's supposed to.

[oldmann]

Have you changed plugs or wires recently?. Sometimes the vacuum line get unhooked. Look for the small hard tube next to the cheater hoses that go through the firewall. Its likely unhooked or cracked.

[oldscsc]

Have you changed plugs or wires recently?. Sometimes the vacuum line get unhooked. Look for the small hard tube next to the cheater hoses that go through the firewall. Its likely unhooked or cracked.

 

There wasn't a small hard tube next to the heater hoses that I saw. I'll double check in the daylight tomorrow. The plugs and wires aren't new by any stretch.

 

A little more info: when I crank up the heat, its hot for less than a second. It's hot then cools off quickly after turning the fan on. Sorry this wasn't in the original post.

[rogerf]

It's hot then cools off quickly after turning the fan on. Sorry this wasn't in the original post.

Sounds more like the heater core is constricted from corrosion and/or not getting good water flow. Most vehicles have some form of flow-control valve...make sure this is working. If that is working, replace the heater core or have it cleaned.

[oldmann]

If its a blend door problem vacuum check to see if the defrost is working. When there is not vac. the defrost is default for safety reasons.

[taylorlawrance]

Im having the identical problem right now on my '00. Im going to back flush the heater core, and replace my radiator cap because its the original one, and when I remove it there isnt any pressure released.

[redvett]

The last truck to use vacuum for the heater actuators was the RV trucks, 1988 GMT400 and later are all electronic.

[oldmann]

Open mouth insert foot.

[sonjaab]

Try the blend door reset procedure:

 

Blend door reset procedure:

 

Look for the HVAC fuses (2?) under the hood.

 

Pull the fuses for about five minutes, reinstall it then turn the ignition on don't touch the controls for another 5 minutes. The system will run through all the settings.

[oldscsc]

Just a follow up:

 

I flushed the heater core out today. Sediment/other junk only came out of one side for a couple seconds, none on the other side. Wasn't too confident it would work but I'll be darned if the thing doesn't burn your feet now. Problem solved!