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Relays kicking out

X

XJjamez

NAXJA Forum User
Location
trion ga.
1996 xj country
4.0 unknown year other than newer than 96 but does not have coil packs
aw4 to match motor
PCM to match motor
TCM to match 1996 jeep
all other wiring stock to 1996xj
Relays kick off. The electric fan and the A/C clutch relays, when removed and put back in, will power fan and clutch for a split second then kick off. These are new relays. I've ran a small ground wire to one side of the fan relay, and it makes it work.( just to be able to drive it with no worrys of over heating ). The A/C compressor will kick on if the switch side of the relay is jumped, but only did this as a test as the A/C is not necessary to drive the jeep. Is this common? Possibly bad grounds? Where do I look for them at? I know one from batt to block, and one from head to firewall. Where else? Or am I barking up entirely the wrong tree?
 
Why does it not have a 1996 PCM ?

As long as the engine sensors are 1996, the PCM does not need to know, and does not care, how old or young the engine block is.
 
Previous Owners. Check out "passed around jeep" thread for the story in it's entirety. this is the PCM I am running. If someone can positively I.D. it I would know more than hear say.
lxgidjV.jpg

Would the PCM have anything to do with the relays not staying switched on? Was tinkering it earlier and found the fog light relay, witch is not in the PDC box, is behaving the same way. I can feel them switch on then off, click click, click click.
 
Searched the Chrysler P/N (dhuu) came back as a 96 Grand Cherokee. Dont know if that makes a hill of beans or not being that it's in a Cherokee country.
 
I can also jump the switch side of the fog lights and they too operate. All three relays in question have voltage on the magnet side, according to Fluke meter. I think that next I'll try jumping the switch side and measure the voltage on the magnet side to see if it remains constant before and after the switch side is closed.
Is there such a ground contact 704? Not for sure on the # as that they get blurry when zoomed in. it's the ground for the component side of the fan relay according to http://s1044.photobucket.com/user/MudderChuck/media/ACschematic.png.html. Perhaps someone could point me to the location of it.
However this would not explain the fog light side of things.
 
I can't say specifically that an incorrect PCM would cause relay issues, but the obvious first step is to find a compatible XJ PCM.
 
Didn't find a ground behind pass side kick panel. Did have loads of fun putting the SOB back on. Only thing under there that looked out of place is what appeared to be an old Fm antenna wire. Why there were two I don't know, but the one that wasn't hooked up did fall apart when I plugged it in and unplugged it. While hooked up it did not fix the relay issues. Was grasping at straws I suppose.
Anyway went back to the PDC box, flipped it over and found this;
6gJYvz9.jpg

Promptly went about fixing this. Piece of an old metal house electrical box, a 5/16 drill bit and three short self tapping sheet metal screws and the box was fixed. (Sorry no pix of the fix, was racing daylight.) The relay issue however was not.
As far as the correct PCM, HOlyCOW that's a lot of dough to through at it, however I did check RockAuto and the part #s do differ. I figured that it was the wrong one when I noticed that the black plastic cover didn't fit. correctly.:bawl:
Guess I'm now on the hunt for the correct PCM.
Any one looking for a MJ PCM.
"Life Is Good":cool:
 
Not sure how the older XJ PCMs are set up, but on the newer ones the PCM controls the ground side of the circuits of the fan, and A/C relays. Now that being said the A/C system isn't going to run if it's over, or under charged. Does the fan not run and cause an overheating issue once it gets hot? I know on my 99 the cooling fan rarely runs even in the summer unless it's a really hot day and the A/C is on. It pretty much stays at 195-220* all the time on just the mechanical fan...
 
A/C is charged to about 29 lbs. Aux. fan won,t kick on by it's self even if I jump the thermal switch. It will come on (fan) if I supply an additional ground jump to the negative side of the magnet side of the relay, however it will not shut off (runs constantly).
This afternoon I'm going to try to contact the parts guy that the PO got the MJ PCM from and see if he might have a correct(small) one that I could try to see if it makes things work. If so perhaps he would consider a trade, or at least knock some off the price in exchange for the MJ PCM.
 
If you are reading 29 PSI with the A/C compressor OFF; then I can guarantee that your system is low on refrigerant charge. I would expect the system pressure to be around 60 psi on the suction side with the compressor OFF; depending upon what the outside air temperature is.....
 
Jumped compressor to check pressure. Found a small size PCM for 50 bucks, but-of coerce there's a but- it's suppose to be for a 2000. Tried to cross reference the part # and it's a few digits short. 56041. Should I give it a shot?
 
That's what I was thinking, however this is the same guy that sold the PO of my jeep the drive line that's in the jeep and billed It as a 2000, but the engine does not have coil packs, the aw4 had a four ping OSS rotor, and a NP231J transfer case. Leading me to believe that the parts guy does not keep good records of the parts he pulls. Or could it be this; The parts guy has told me that the drive line came out of a mail carrier jeep that was retired after it rolled off into a ditch. We have some big ditches here in the south. Anyway, could these mail jeeps have been assembled with oddball shelf parts making the PCM the correct one for my distributor motor? Perhaps from the same mail jeep donor. It's also kind of weird that the part # is three digits too short.
 
A 1996 XJ requires a 1996 XJ PCM. If you have an automatic, the donor XJ should have one also.

Some parts interchange over a wide range of model years, and some do not. As long as the engine sensors are 1996, the PCM does not need to know, and does not care, how old or young the engine block is.
 
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