Giving in on Heater Control Valve

OK, I have an 88 MJ and 90 XJ. I converted both to an open cooling system with post-HO parts. I had heard that doing this would increase the heat in my cab. So...I've NEVER had any problem with the XJ..no heater valve...straight thru the core...no unwanted heat thru the vents.

The MJ however is hotter than %&@# w/o the heater valve. On this and other forums I've previously spewed that running the hoses straight thru the core WON'T affect the HVAC system. My experience now is - NOT!

...any thoughts why the two Jeeps are different? I get hot heat with the HVAC turned to OFF. I bought the valve, but I don't want to ruin it in a puddle of coolant unless I investigate.

Check the adjustment of the blend air door under the dash. Cable operated with a sliding clip. It's not closing completely is my guess.

YUP, funny how sometimes the jeep makes us all look dumb sometimes.

i remember avoiding a conflict about this maybe 2-3 weeks ago (my xj is one of the ones that gets hot from the no heater valve).... and to top it off... my dads heater core is leaking on his mj! good thing he's got slush mats.

ParadiseXJ said:

...any thoughts why the two Jeeps are different?

Click to expand...

AFAIK, they're not. Parts guide lists Cherokee, Wagoneer and Comanche in the same diagram.

My guess is your blend door cable came off or is broken. Do you feel "resistance" when you slide it back and forth?

Saudade said:

AFAIK, they're not. Parts guide lists Cherokee, Wagoneer and Comanche in the same diagram.

My guess is your blend door cable came off or is broken. Do you feel "resistance" when you slide it back and forth?

Click to expand...

Will check that out this eve after it cools off. Where would I be looking for cable (or lack of).

Photo anyone??

So, sounds like if it IS in fact a blend door issue that I still don't need the HCV. Then I can go on spewing, after I fix it that is.

Under passenger side dash. Poke your noggin under there and move the control from cold to hot. You'll see it.

my MJ is fine with no HCV, converted to open cooling system. I have a brand new HCV on te shelf I bought to finish the conversion, then just never installed it.

87manche said:

my MJ is fine with no HCV, converted to open cooling system. I have a brand new HCV on te shelf I bought to finish the conversion, then just never installed it.

Click to expand...

Same deal with my XJ. Never installed it...never had to. I'm still working on the blend door thing, I haven't looked at it yet...gotta work.
We'll see

Well, it was a stuck blend door. Just enough surface rust on the shaft to keep the thing from moving. I lubed it up with some regular old 3 in 1 oil. Works perfectly now.
Returned $25 heater valve, going to run it straight thru the core, like I've spewed.

...and on a side note, the A/C in the XJ had been warm so I went to re-charge it. CA now has a $10 core charge for the empty r134a cans and they need a special adapter now. The whole set-up for a re-charge was $50, BUT as luck would have it the main wire was disconnected to the compressor. Hooked up the wire. A/C now velly chilly. Checked with gauges, full charge. Returned $50 r134a thingy.

So, my problems with HVAC are solved and I'm $75 richer...hmmm, should I take the wife to dinner or buy more parts???

Take her to dinner..........