RunninKurt

1998 Jeep Cherokee SE 2 Door 2WD

This is my first "winter" with this Jeep, so could be reoccuring, could be a new problem.

Back Story:
Water pump was seeping, so I changed it.
Left my T-stat in, as the operating temps have been and still are fine
Backflushed the Heater Core (only one back flush, but got plenty of gunk out)
Changed lower radiator hose
Refilled coolant system with premixed 50/50

Recently the defrost wasn't working, at the same time, I noticed the temp while using heat and defrost wasn't very warm.

I diagnosed the defrost as 1) A loose belt was causing an inefficient compressor and 2) I am assuming low freon pressurse causing rapid cycling of the compressor.

I am ok with poor defrost performance, but the poor heater I'm not ok with.

I flushed and backflushed the heater core again, then blew it out with air.

Checked my blend door, cable is "loose/less than tight" at full cold and full hot, but the door actuator moves 90* as it should.

The input hose to the heater core gets hot, and the output is "less hot"

What is my next step?

RTorrez1

Sounds like you need to flush the heater core more then just one time.

RunninKurt

I did. Says it in my time log up there.
The first time I only back flushed, the second time I back flushed then forward flushed then aired it.

Turbo X_J

"got plenty of gunk out"

When dealing with a poorly maintained cooling system total replacement is usually the cure, $150-200 one time & you are done.

RunninKurt

Thanks for the input, after narrowing it so much I came to the same conclusion.

Rotorhead

Forgive my ignorance, but what does your A/C compressor have to do with defrost?

RTorrez1

This is telling you that you do not have proper flow either you still have some crud in the heater core you you t-stat isn't operating correctly. Just because you have flow doesn't mean that it is a proper flow. I would recheck it before throwing money into it and it doesn't fix the problem. putting a new radiator and everything else won't help if the heater core isn't replaced or at least cleaned properly. Just a suggestion.

RTorrez1

Your AC compressor kicks on when you turn on the defroster. That is if you have AC.

RunninKurt

I apologize for the misunderstanding.

I may try a flush kit with chemical additives this weekend or something... Last ditch effort type deal

KJamesJR

Really? I didn't even think my compressor worked though I always use a (working) defrost. I wonder if I can actually charge my a/c now...

Rotorhead

Ok. But why?

cruiser54

To pull the humidity out of the incoming air before it goes over the heater core.
So your windshield doesn't fog up.

RTorrez1

Yup! On my 65 Chevy P/U I have no AC and when I do turn on the defroster the window will fog up more before it clears up and everything is nice and hot.

Rotorhead

Interesting



The more you know...

CCKen

Some FYI stuff. From my Owner's Manual. Read "Window Fogging".