Heater blows warm

[MTBLAZER89]

With the slider on full hot and the engine running at 160-180 I get warm air. I think the fan or the vent/floor kinda sucks too, but the air that i can feel is no more than 70 degrees. Was a chilly snow run the other day!

I was thinking heater core, but I have no leaks and the engine never gets hot. It did get up to 200 once trying to climb a snowy hill. The air did get warmer, but not anywhere near normal.

 

[readymix]

Does it have the AC heater box with vacuum control?
Might just have a sticky blend door.

 

[Blue85]

First thing of course is to check the coolant level. Then make sure the blend door is closing off the cold side so all air is going through the heater core. Then back flush or replace heater core. Or maybe the back flush is easier than getting to the HvAC ducts.

 

[4xcrazy]

Not running the right t-stat won't get you any heat either. A 160 will not blow hot air in cold winter. Always running 195's and always had nice hot air. Even tried a 180 once, there was a pretty significant difference in heat as well

 

[ccarley]

Having recently replaced my heater core, let me tell you how nice a new one is!

My original one, being what looked like brass, wasn't putting out that much heat. It would take my entire 20 minute commute to start to feel heat coming out of the vents, even though the engine had reached temp probably less than 10 minutes into my drive.

With the new aluminum heater core, I have heat before I leave my house. As soon as the dash gauge starts moving, there is heat coming out of the vents. I do have the broken link on the door that selects which vents to blow out of, but I do still have heat! Heck, it works better than my wife's 2001 Volvo at the moment. And my slider didn't get adjusted, so I can't even get the blend door all the way to the hot side!

I wish you luck; that would be the first thing I would do. I understand it might be cold there though... Oh yes, and if you do tear into it, I'll tell you all about the double and blind nut on the heater box that's on the firewall

Clay

 

[dyeager535]

How are you heater hoses connected? Just making sure they didn't end up connected to the water pump and radiator, which will lead to minimal fluid movement through the core.

Pretty basic, but hose routing is a lot easier to fix than blend door problems!

 

[6.2Blazer]

Not running the right t-stat won't get you any heat either. A 160 will not blow hot air in cold winter. Always running 195's and always had nice hot air. Even tried a 180 once, there was a pretty significant difference in heat as well

I was thinking the same thing when I came upon this reply. My '90 has the 6.2 and runs cool when not under a load, so always runs well below the t-stat temperature when cruising through the woods. With the engine at 160F the heat is just warm also and if the outside temp is very cold it will be chilly.

 

[MTBLAZER89]

Yes its an AC truck.

Coolant level is good and 50/50 mix.

Ok I'll try the back flush first. Nothing has changed with connections or hoses on the truck and it used to work great! I've wheeled with no doors and no top for a couple winters now and usually it blows enough heat to keep my warm as long as I'm going slow and there is no wind.

I thought maybe one of the doors too because it also doesn't seem to be blowing as strong.

 

[4xcrazy]

Is this one of the TBI trucks you are referring to? and as you previously stated, you say it's running nice and hot at 160-180???

 

[MTBLAZER89]

Yeah it's my K5 with the 350. Stock gauge so it doesn't have numbers in the normal operating range, but about 1/3 of the way up the gauge. 210 is half way so I was just guestimating 160-180. It gets up to 210 when I'm rodding on it with little airflow through the rad. Temp seemed completely normal to me.

 

[63chevyll]

Sounds like a plugged core...
Well. Internet diagnosing leads me.that way

 

[black dawg]

Make sure the cable for the blend door is adjusted.
On my stuff anyway, I have to adjust the cable a little in the summer to get nice cold air, and then again in the winter to get good heat.

 

[paratrooper307]

Check the heater ducting behind the dash while you're at it. Mind had become disconnected over time and a lot of the air wasn't getting routed to the cab.