charging problems

I have a 1992 Cherokee, with 4.0 Litre High Output engine. The alternator checked out ok. I cleaned the battery posts, clamps, and ground stud above starter (on side of engine block) with its nut , 1 large wire end and 3 small wire ends. The dash check engine red lite is on , so , checking the brain I get Code 41. The voltmeter reads 14 for a while, then drops to 0 for a while, then back to 14. These are at unregulated times, and I have run out of places to look. Can anyone, please, help me with your knowledge and ideas. Thanks, royboy

On the voltmeter, when I said 0. I meant the battery base rate of 12 volts. royboy

Hallo, '92 owner.
My feeling tells me it is maybe a ground problem. (hopefully)
Ground from block to firewall or ground from battery to fender.
You can test it very easy with your DMM by Ohms.

'92XJwim

If you mean checking with the dash voltmeter, they are very unreliable. You need to check directly on the battery with a handheld voltmeter to isolate the issue between actual function and dash gage.

Sounds like an intermittent open between the PCM and the alternator, check and clean the harness connectors.

Whats the PCM?

Powertrain Control Module-- the engine/body computer

I just went through this on my 92.

The PCM contains the voltage regulator, not the alternator. I had a low voltage issue and replaced the alternator and then found that did not fix the problem. Subsequently changed the PCM and got the right voltage.

On the back of the alternator is a big wire that feeds the battery, then on the lower side is the "field control" which is two terminals (ring type) make sure they are clean and connected, because one comes from the PCM to provide voltage to excite the alternator and without that, you don't get any output from the alternator.

My story (on the road trip) is a long one, but the short of it is I changed the alternator in the mountains in a snow flurry, later changed the PCM and then after travelling some distance found where one of the field terminal stanchions had broken off and had to change the alternator again!!

BTW, I am putting my Jeep out to pasture and bought a Toyo 4runner (used of course)!!

Sig220 said:

BTW, I am putting my Jeep out to pasture and bought a Toyo 4runner (used of course)!!

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HERETIC!!

joe_peters said:

HERETIC!!

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Maybe I should explain a little more.......my last trip in my Jeep cost me more then it did to acquire it and get it road worthy..........which was about 5 years ago. My road trip is from TX to CO about 2000 miles roundtrip. (Annual elk hunt!!) This was my 3rd personal Jeep. On that roadtrip, I replaced the fuel pump, alternator, pcm and battery.

I replaced it because I don't want to have to work on it in the snow anymore and get back to work 2 days late!! So I gave it to a friend who has a bit of property for it to run on and in return, I get hunting privileges. I won't be Jeep-less, as my daughter still drives a 2001 Cherokee, alas but only a 2WD.

In my comparison, I liked the Jeep size and height more......the 4wd has always pulled good and it was relatively cheap to work on. The T4R is a little bigger, carries more, pulls more (rated at 5000 pounds) and has more creature comforts.

Gas mileage is about the same, but the Jeep is cheaper to work on.

If somebody besides Dodge took over the Jeep and made it the same size as the old Cherokee I would probably sport one in my driveway!! Jeeps have always been special.

Bump

Will an PCM outta an 91 5-speed interchange? His is an 92 automatic. Both are H.O`s

just went through this 2mths ago. had no voltage from alternator for several minutes until it warmed up a bit. Did that for about a week and then coming home from out of town (thankfully it was during the day) the alt went DOA. Got out the volemeter and confirmed that the alternator was not putting out voltage. Pulled it off, had it bench tested 3 times at Oreillys and twice at Autozone, the damn the tested good each and every time - went with my gut instinct and replaced it anyway. Guess what, that was 2mths ago and its been running great. DO NOT TRUST THE MACHINES AT THE PARTS STORES WITH ANY CHRYSLER ALTERNATORS! If you think it's bad, it probably is. If you don't want to gamble $100+ on a new one, get a salvage

BTW - I have a 92 cherokee, 4.0HO with a auto trans

Thanx for all the help, it has to be the PCM or alternater(even thou it checked out ok on Schucks machine. Will a used PCM from 4.0 w/ 5spd. work in a 4.0 w/ auto trans.

I'm going to hazard an educated guess that NO, you can't interchange the PCM, based on the listings at rockauto.com and it specifies different part numbers for the manual or auto equipped vehicles.

Well tried an differant PCM today and that wasn`t the issue. So i pulled the alterator and tomorrow will replace that and we`ll let you know. Thanks for all the help

Changed out the alterator and Problem is fixed. Thanks again for all ur help.

It was the alternator, thou it checked out ok, twice. Cherokeefever, had a spare PCM that he put on, to check the charge & NOTHING happened, BUT a rebuilt alt. did the trick. Thanx everyone for your help, & a special thanx to CHEROKEEFEVER for helping me figuring it out & the work fixing the problem!

royboy said:

It was the alternator, thou it checked out ok, twice. Cherokeefever, had a spare PCM that he put on, to check the charge & NOTHING happened, BUT a rebuilt alt. did the trick. Thanx everyone for your help, & a special thanx to CHEROKEEFEVER for helping me figuring it out & the work fixing the problem!

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This is the second recent report of bad Nippondenso PCM controlled alternators that tested good, but were found out to be bad.

Seeing a trend here?