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Bypass switch for A/C?

X

xjnuttier

NAXJA Forum User
Location
lancaster, pa
Hey guys I was driving down the road the other night, and enjoying my terrible XJ heating system, on my 98. LOL it is warmer than last year, but still kinda cold. The reason I went into the story is cause the wifey was sitting there beside me, and said why can't you have heat on your feet and top vents? it only shows witht the A/C on... Well I started thinking about this a little, and thinking back to a thread about overriding the cooling fan, and they tapped directly into a wire going to the computer, and were able to make the fan work like normal or be on switched power, and us as necessary. Well my question is, Can you bypass the A/C compressor the same way, and enjoy ALL the HVAC settings of the XJ? By the way we had a blast palying in 3-4 foot drifts here across southern PA...
 
Thanks.

What happens if you simply unplug the compressor?
 
Just pull the compressor relay out of the box. I do that to mine every winter. I know it makes the defrost less effective, but it hasn't caused any problems for me.
 
I can appreciate the simplicity of your responses,a nd most folks would just go down that alley, but I like to make things more complicated..LOL Anyways, I know there is a way it can be bypassed just like any new car of today, and honestly wouldn't it be nice to just flip a switch inside, and have your compressor kick on, when you wanted it to, and not when you didnt. I know guys have tapped into the wiring harness, to control the aux fan, and run that as deemed necessary, and this concept is on the same premise.
 
and lol since my fog light shitch went to melt down, and I am fabbing up a front bumper, that would be a great place to put the switch for the A/C compressor, or for that fact this would work for on board air systems also....
 
Why dont you start in the on board air threads and see how they control the compressor? Wouldnt that make sense?
 
xjnuttier said:
Hey guys I was driving down the road the other night, and enjoying my terrible XJ heating system, on my 98. LOL it is warmer than last year, but still kinda cold. The reason I went into the story is cause the wifey was sitting there beside me, and said why can't you have heat on your feet and top vents? it only shows witht the A/C on... Well I started thinking about this a little, and thinking back to a thread about overriding the cooling fan, and they tapped directly into a wire going to the computer, and were able to make the fan work like normal or be on switched power, and us as necessary. Well my question is, Can you bypass the A/C compressor the same way, and enjoy ALL the HVAC settings of the XJ? By the way we had a blast palying in 3-4 foot drifts here across southern PA...
Click to expand...

Yes, it is easier than you think. Just unplug your low pressure switch on your AC line. Not sure on the location on the 98, but almost every one I have seen the 4.0 switch is on the filter drier located on the passenger side sub frame near the compressor. Two wires with a round connector. Un plug it and the system will think it is low on refrigerant and will not allow the compressor to come on. Plug it back in for the summer and it will work normally.
 
4.3LXJ said:
Yes, it is easier than you think. Just unplug your low pressure switch on your AC line. Not sure on the location on the 98, but almost every one I have seen the 4.0 switch is on the filter drier located on the passenger side sub frame near the compressor. Two wires with a round connector. Un plug it and the system will think it is low on refrigerant and will not allow the compressor to come on. Plug it back in for the summer and it will work normally.
Click to expand...


yeap, i know about the leads ,and how to kill the power totally, but I want a switch to shut it on and off from the cab, and make it look nice. I know I am not the only person who wants to have full use of the HVAC controls for just heat... and not to have the A/C come on everytime you hit the defrost mode...
 
jdougn said:
So why not just tap the wire where it connects to the compressor and run a switch off that? Would that work?
dn
Click to expand...

I was thinking that, but I didnt know if it would act up with the computer or not? you know throw a code or something... That is why they tapped the wire for the fan switch at the ECU, and that is why I keep referring back to that mod, this is on the same lines of wiring mods, just another function to bypass,or override...
 
There wiring for the compressor goes right through the engine bay, very easily accessed. Installing a switch there would be simple. However that would only stop the AC from working. When you turn the dial over to AC, it closes off the heater system completely.

You would need to wire the fans up directly to a switch, which I think is what you are suggesting.
 
xjnuttier said:
yeap, i know about the leads ,and how to kill the power totally, but I want a switch to shut it on and off from the cab, and make it look nice. I know I am not the only person who wants to have full use of the HVAC controls for just heat... and not to have the A/C come on everytime you hit the defrost mode...
Click to expand...

Just run one of those wires through a switch then.
 
You absolutely can bypass the AC compressor, I do it all the time by pulling the relay for the compressor. That makes the AC switch into an auxillary fan switch. Too easy!
 
On my 00 I tapped into and added a switch to the a/c sense wire on the hvac panel plug (the black one with seven terminals). If you are looking at the contact end of the black plug, the a/c sense wire will be the second from the left (or in the #6 spot, same thing).
HTH
 
iirc the ZJs have the ac off option on the hvac panel. maybe you can steal the controls from that wire the ac switch to a relay that breaks the ac clutch circuit. i don't see why it would not work as a test just unplug you compressor and run it like that if you don't have any issues then it would not be a problem to have a relay cut power to the compressor.

pulling the relay or unplugging the ac is a pita becasue i don't want to get out and plug it back in when i want to use the ac. i had my fog lights that way and i just never used them.

i might do something like this when i redo my fog lights
 
natep1 said:
On my 00 I tapped into and added a switch to the a/c sense wire on the hvac panel plug (the black one with seven terminals). If you are looking at the contact end of the black plug, the a/c sense wire will be the second from the left (or in the #6 spot, same thing).
HTH
Click to expand...

So in other words you have already done this mod, and it works perfectly.. That is awesome, that is what i am looking to do then. What type of switch did you use? I was thinking of a factory button style I can incorporate in the HVAC controls if logistically possible.
 
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