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AC/Blower Fuse Issues

Kidd XJ

NAXJA Forum User
Location
Alta Loma Ca
Hi all, I have read many posts about this problem and have spent a lot of time and done a lot troubleshooting and apologize in advance for another post on this issue.

My AC is all new: (92 XJ 4.0)
new compressor, new dryer, new condenser, new high pressure lines, new fan resistor. Worked great for a couple weeks then all h**l broke loose.

I have done the trouble shooting: disconnect compressor blows fuse, disconnect blower blows fuse, disconnect low pressure switch use jumper blows fuse, disconnect low pressure with no jumper no AC but fan works and the fuse does not blow. I have checked all wires as best I could and see no issues.

So this is where the fun begins.
I am not that great with electrical so I took it in to an AC shop here in Rancho Cucamonga to have the wires/circuit tested. I told the shop that I felt the low pressure switch circuit or maybe the switch itself was bad. Shop does the testing tells me all wires/switch is good but says the blower motor is pulling too many Amps. I didn't want to pay over $100 to fix so I took it home and I replaced it myself. Guess what still blows the fuse.

I am fairly certain it is not the pressure switch because when using a jumper across the plug the fuse still blows, and based on what I have read if it was the switch using a jumper/bypass the AC should work. I have connected a multi-meter to various wires and all seems good till I test voltage on the low pressure switch plug. The Green wire side puts out 24V and the Blue has 12V. I am no expert by any means but I am fairly certain I should not have 24V anywhere.

If anyone has a clue as to what may be going on here please let me know what to look for???
If anyone knows of a really good electrician or AC shop around Rancho Cucamonga/Ontario I am all ears.

Thanks in advance, Mark
 
Yeah, that doesn't sound right - I'd expect one wire to have +12V and the other 0V/Ground.

Got a service manual of any kind (Haynes/Chilton/FSM)?
 
How 24 volts appear in a 12 volts XJ,...that is just not right. I have never heard of anything like that on any other vehicle. Are you sure someone did not install a 12 to 24 volt converter in there?

I too had problem with the same fuse going out. It only did that when both the AC compressor and the fan was running at the same time. The fuse bleu by being overloaded. Yes, it was the correct value. I took the fan out a few days earlier to clean the air box. When I replaced the fan, the rubber seal was partially into the air box and touched the fan. Because of that, the AMP draw increased sufficiently to blow the fuse.

By-the-way, I do not think voltage alone causes a fuse to blow. I am in the wireless communications field. Over the years, I have used countless automotive fuses to protect 24 volts and 48 volts DC equipment and the fuses held up just fine.

Check for excess load on one or more pieces. Also check the wires for cracks or breaks in the insulation that allow them to short to ground. If all the pieces are on good order, a correctly rated fuse should have no problem caring the load.
 
Yes I have a Chiltons manual to answer first question I have checked this circuit extensively the best I can and see no bad wires or shorts anywhere. I have opened up the harness all the way to the drivers side along the firewall.

More troubleshooting today turns out my Craftsman multi meter in auto sensing mode just does not accurately test voltage (very odd). I used my freebe from Harbor Freight and voltage is accurate at a little over 13V with the Jeep running. Took the Craftsman out of auto mode to verify and all appears to be ok. As I stated I am not much of a auto electrician but I do my best. I did replace the fan so I will check to see that there is no issue with the fan blade or gasket and report back, but at this time I truly feel that there is something going on with the low pressure switch circuit. Everything works perfectly with it unplugged. No matter what I do everything works until I plug it back in or run a jumper wire across the plug, pop goes the fuse. I cant even get the AC to kick in with the fan unplugged.

Is there a way to jump the AC compressor with the low pressure switch unplugged? What about trying a 30 amp fuse??? Is any of this even advisable???
 
Re: Another AC/Blower Fuse Issues

Well cant find anything wrong with the fan gotta be something else any help is greatly appreciated. I can find no open circuit or grounds.

This has to be one of the most frustrating dilemmas I have ever encountered. Something is just pulling to many amps.
 
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