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A/c wired directly to eFan?

2001xjeepx

NAXJA Forum User
Location
Tennessee
Just started to fix up my wife's 2001 Cherokee XJ classic, 4.0 6 cylinder auto. While I'm driving the Jeep I notice that when the air conditioning or defrost is turned on hat there is a massive electrical draw about every 20 seconds or so. I traced some wires in the engine bay and discovered that someone has piggy backed the wire coming from the A/C into a 30 amp relay directly into the fuse box relay that controls the electric cooling fan. So now everytime I turn on the A/C or defrost the eFan comes on instantly with it. Every 20 seconds or so the fan will turn off for 2 seconds and then back on again causing a massive electrical pull dimming all the lights, tail lights, headlights and radio and dash lights.

My wife told me that the a/c stopped working about 5 years ago and she visited a local shop where a man told her that it was due to a faulty part that he could buy only from Chrysler and it would be upwards of 400 bucks. So instead he talked her into paying 20 bucks to "bypass" this part. So now I have this wiring and I don't know what to look at to replace. Any ideas out there? I wanted to put LED light bars and fog lights but I'm afraid the power pull needed while a/c is on will be too much.
 
2000-01 are programmed to run the e-fan only when engine temps or A/C pressure calls for it to run. Typically, even on the hottest days the e-fan runs sporadically for 30-90 seconds. I suggest you diagnose what this mystery $400+ part is, and fix the e-fan circuit as required. The e-fan should not dim the lights, I would suspect an old e-fan drawing excessive voltage, or inadequate voltage to/from the battery/alternator/e-fan. Naturally, you will want to confirm that the battery/alternator/e-fan/ground wires all have top condition wires and wire connections.

A properly maintained charging system can handle the extra load from some extra lights. FYI, LED lights draw very little voltage.
 
Here is another possibility.
The 2001's A/C compressor and the the cooling fan are controlled separately by the PCM, they have no other common control part.
The only semi-legitimate reason to do a bypass like this is if the Aux Fan's driver, in the PCM, is burned out and cannot operate the fan. Then, the only way to have the fan operate is to use a bypass, with a relay's trigger wired directly to the A/C's compressor coil.
You can set the fan up to be operated by a separate switch but that requires paying close attention to the coolant temperature

Rebuilt PCMs cost around $300, so that may be the $400 price quoted to repair it.

30-amps is way too much amperage for the fan, it should less than 10-amps, when running.
 
Well that sounds like a possibility. The pcm being burnt out. I'm going to try unhooking the 30amp relay that's wired into the factory relay, starting up the Jeep, letting it warm up and see if I can get the fan to come on naturally. Maybe I can do some better troubleshooting.

But here is what my wife told me. She said that the A/C was not working when this was done. Apparently he wired this up to make the a/c work, not the fan? I'm so confused
 
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Okay upon further inspection I found that the clutch is piggybacked directly to the 30 amp relay previously mentioned. the air conditioning system cycles every 6 to 10 seconds causing the electric fan to engage and disengage along with the constant cycling of the AC unit,

if I unplug the relay and run the Jeep, the AC still cycles and blows fair cool air but the a fan does not come on only when I plugged the relay back in does it run.

Does this sound like a faulty pcm that someone was trying to bypass? Pics of wiring above
 
The a/c high pressure switch controls both compressor and fan on the 01's. It tells the pcm to turn things on/off if conditions are not correct. Santech still makes the OEM unit for about $30, and it installs easily.

I would discard the bypass nonsense, and change out both high/low pressure switches before going any further. Also, ensure proper refrigerant charge before testing. The pcm should be the last suspect in this case.
 
I agree with Jesse my 00 factory service manual (which I assume is the same) has the A/C high pressure switch go into the PCM at C3 Pin 13 which is for "Radiator Fan Request" and C3 Pin 1 on the PCM is the "A/C Compressor clutch relay control" the only other PCM input is C3 Pin 23 for "A/C Switch Sense" so when the A/C is turned on, the PCM gets this info as well as if the system is charged via the high pressure switch it turns on the fan. The only other A/C electrical items are the A/C relay. I have already told you the PCM is the control for the rely. The only other connections to the relay are 12v constant, 12v from the ignition, and output to the compressor clutch. Of course the radiator fan has its own relay. Radiator fan relay control is via the PCM C3 Pin 2. The only other connections on the radiator fan relay is 12v constant, 12v ignition, and output to the radiator fan. So everything does go through the PCM which controls the radiator fan. The only other time I have seen A/C systems cycle like that is when they are not fully charged. But I would have to start testing the wiring to figure this one out if the system is charged correctly.
 
Also if you put fog lights or a light bar on it, I recommend using the existing wiring and relays already in the PDC (power distribution center). Our Jeep already have 2 existing relays for the fog lights. and the fog light wiring should be behind the bumper.
 
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