Heat not working

[mysery1]

Had 99 jeep that would not blow hot air and it turned out to be the water pump. There were no vanes left on the pump.

 

[scott_williams2]

Ok so I went back to the basics and I checked the hoses after a 30 minute trip they weren’t reversed. However The outlet hose was a great hand warmer in the cold but the inlet hose was hot enough to send u to the hopsital. so the coolant going out is a lot cooler than the stuff going in. Does this mean my heater core is bad???

 

[east302]

It may be restricted if the outlet is that much lower than the inlet. I don’t remember there being that noticeable a difference on mine - neither is particularly comfortable to hold for a long time.

Flushing the core may help...see if anything comes out of it.

 

[scott_williams2]

It may be restricted if the outlet is that much lower than the inlet. I don’t remember there being that noticeable a difference on mine - neither is particularly comfortable to hold for a long time.

Flushing the core may help...see if anything comes out of it.

Just finished flushing it and no difference. The heater still doesn’t work. However I noticed the ac compressor kicking on and off wit the heat on idk if that’s normal or not but I unplugged the compressor and now it’s blowing hotter but not near what it should blow

 

[scott_williams2]

I just don’t understand why it isn’t getting heat. The core inside the box gets hot and the box is hot why isn’t it transferring to the vents like it should

 

[df2x4]

However I noticed the ac compressor kicking on and off wit the heat on idk if that’s normal or not

Did you have the defrost vents selected on the dial? If so that's normal. The compressor runs to remove moisture from the air when you use those.

 

[east302]

What is the air temp at the vent when driving? I wonder how it compares to GM spec table of outlet temperature vs ambient.

I’ll try to remember to check mine in the morning just to compare. I’m in Jackson so outside temps should be pretty close.

 

[98 Nitro]

Are you sure you the recirculation door on the passenger side is closed? The little motors go bad alot and make a ticking noise everytime you start and turn off the truck so some people unplug them as they are a pain to change behind and to the right of the blower. If that is the case it is not going to get that hot, you might even have some cold air come in.
Also you might try the old cardboard in front of the radiator trick.

 

[Knuckle Dragger]

I don't know if it was related to the LSx swap in my truck but I had to put a restricter in the line out on the heater core to get the heat to work for me.

 

[east302]

Checked mine this morning...

Outside temp 34
Floor and panel vent made no difference, it was around 130 at idle.
Driving 40-mph it went up to 145. It probably would have gone a little higher but I have a short commute.

Putting it on recirc added about 5–10 degrees.

This was with the a/c on and blower on high. Turning off the a/c made no difference. Heater core is original (1998).