No front heat-?

[BigRoryG]

So I put in new thermostat and my front heat still doesn't work. The rear heat seems to work fine and gets hot in a reasonable amount of time.

The fans all work properly but will only blow hot on rare occasions and usually only after I've been driving for more than 2 hours.

Thoughts?

[BigRoryG]

that's a 95 Suburban 2500K 4WD, by the way.

[redbird2]

Have you check the hose coming and going from the heater core, one hot other should be some what cooler not cold, could be plugged core, how is the are flow good or so/so if it so/so i would try blowing out the core acroos the fins to get dirt out of them.

[JeffMD]

I have had the same problem in my '94 K2500 Suburban. You might want to check the position of the heater core in the duct itself. I dont know how it was originally secured in there but I found mine laying on the bottom of the box, with the airflowing over top of it instead of through it. Once I repositioned it and closed everything back up it was like a completely different truck!

[BigRoryG]

Rookie Question: I just unbolt the dash to get to all that nonsense, yeah?

That would make sense... I noticed that the dash became very warm occasionally when I tried to use the heat, and it did sometimes work. The flow overall in the system has to be good, because the rear works fine and my SVO tank warms up nicely.

Thanks for the help. I'll get into that.

[JeffMD]

On mine it was just a (I think) 7mm. socket to undo the fasteners on the black plastic duct work under the right side of the dash. The "right" way probably involves a lot more work, but I got my truck used and some of the duct was already cracked so I was able to just persuade it a bit.

[Warren96]

Try back-flowing it with your hose before you take this thing apart,you may have scale in the core causing loss of enough flow.The core will still get hot if there is no air blowing across it.

[ZZ]

I don't know how much different the 90 model is from you guy's trucks. Mine has the electronic control. I don't get near enough warmth if I put it on the floor. I get cold when it's on the floor. I have flushed and back flushed the heater core and it is not stopped up. I think the motor that moves the temp door doesn't close all the way for heat. If I set it about half way between the vents and the floor; I get plenty of heat.

[BobND]

Just because you have flushed the heater core repeatedly, and it flows well does not mean is is not partially blocked.

Time and again, up hear in the COLD north, I have had to replace a heater core that seemed to flow well, but heated poorly. The difference a new core makes can be almost unbelievable.

[ZZ]

Let me ask you this. If it were blocked; would I get the good heat that I do by running the vent & floor air flow mixed?

[Bnave95]

Just a thought,On vent you bring out side air through the heater. On floor heat it is to recycle cab heat. My heater hose is hot going in and only just a litte cooler coming back out.
I've heard of some not getting hot when running 180* stats. 180 is hot :D
So can the flaper get stuck some where in between?

[ZZ]

I know I always used 180's in gas burners the year round and usually had all the heat I wanted.

I put a 195 in my truck the past two winters but decided against it this year because my "gooseneck" leaks too easy if I don't seal it just right.

[Bnave95]

180 Stats may be to cool for winter but I run a winter cover that also has two flaps that can be open or closed. Mostly I run them open that alows air to the coolers.
Also it only takes 5 mins. of running to get heat.

[rustypig]

As others have alluded to, I would check your flapper door positions, ie... controller and cables. They are much more likely to be inop than coolant flow. My general theory...go after "what moves", "what's electric" before anything else. Good luck!