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Heater Core Cutoff Valve/Bypass??

Sleepydog

NAXJA Forum User
Location
Clarksville, TN
I just got my fourth XJ - Its a 2000.:laugh3: It runs great, looks great, etc...

Only problem I've noticed is that the ac is not super cold (cool, but not cold), and the temperature control dial does not work at all (all cool, all the time, no matter what the dial position).

I noticed that the previous owner had installed a shutoff valve in the heater hose going into the core. It was turned off (no hot coolant flowing to core). I turned it "on" and now the temp control dial works perfectly. Makes sense, considering it now has heated air to work with.

I cannot understand why the p.o. would have installed the valve. The core is not leaking at all, and the ac works (although it could use a charge).

Is there any advantage to having the cutoff valve?
 
Someone put a shutoff valve in mine too. I never touched it but always wondered what it was for. I've even seen 1 or 2 in the JY with them in it.
 
The older XJ's prior to 97 had the vacuum actuated shutoff valve. After that they got deleted and coolant was always allowed to flow to the heater core.

I was reading up about F350's and some guys added manual shutoff valves and saw an improvement in the A/C efficiency....AKA not having to use MAX AC anymore and still getting it just as cold in the cabin, or colder.

So I'd say the valve has some merit.
 
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