I'm getting, what I consider, low and odd heater output. My Temperature gauge indicates 210 degrees on the coolant. But I'm getting very low vent temps. I'm not getting hot air out of any of the settings either "floor", "defrost", or "vent". Its on the "vent" setting where I noticed the unusal output. There are four vents on the dash. The two on the drivers side only get 90 degrees vent temperatures, and the passenger side two vents only get about 60 degree vent temperatures. This is just a regular 1999 Cherokee XJ 4.0L with no zone heating. I don't understand the low vent temps and I REALLY don't know what would create the difference in the left and right vents. Either way, it's getting to be a pretty cold ride here!
Thanks for your help!!

 

Can't really help u any but I noticed on my xj tht if I put the setting to ac wen I have my temp to the hottest it can get it does blow alil harder. Sorry couldn't help u much but if I helped u get alil more warm air flowin n ur jeep il ltake it

 

Couple possibilities...

1. Heater core clogged (low temp), probably needs to be flushed.

2. Ducting broken/disconnected in dash (different temp).

 

Don't really understand the temp being different on each side but it sounds like something may be wrong with the heater core it may be clogging up because of dirty antifreeze. I have heard of animals like mice building a nest by it to so air just goes around it instead of through it. There's also a valve on the pass side under the hood close to the firewall that looks like a 4 way plastic fitting with a vacuum line going to it maybe its bad. A new one is about $20 at parts store I broke mine in half making room to change plugs 2 months ago.

 

thanks! I'll check both!

 

I'll look into a heater control valve. I didn't think to check for something like a nest inside the heater ducts. Both would explain the low and different vent temps!

 

No heater control valve on 99 I forget which year they stopped, but most people do away the the HCV anyways. Good point about the nest, my dad had this happen in his old ranger but he had heat, just wouldnt blow the same side to side.