Computer keeps cooking itself
04-11-2012, 05:44 PM
#1
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Year: 1993
Model: Grand Cherokee
Engine: 5.2
Computer keeps cooking itself
I'm starting to get fed up with this issue. Every time I think it's fixed it just happens all over again. I narrowed it down to this... The computer controls the regulator for the alternator. The computer thinks the voltage is low, it's over charging the battery with 15.5 volts. It's cooking batteries, alternators, and computers. I changed all 3 at the same time. Cooked 1 battery, and then the computer fried. Other then changing the entire main harness.... What can I do to stop this from happening? I'm out of ideas here!
04-11-2012, 06:03 PM
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Year: 2000
Model: Cherokee
Engine: 4.0 I6
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04-11-2012, 09:58 PM
#9
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Year: 1995
Model: Grand Cherokee
Engine: 4.0 with all of the noise and clatter
You need to check the grounds and check for voltage drops between the alternator and battery.
04-11-2012, 10:05 PM
#10
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Year: '99
Model: Cherokee
Engine: 4.o
Why not check the rest of the harness's? A short anywhere could be causing this and most likely is. So trans harness? dash harness? chassis harness?
04-12-2012, 09:57 AM
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Year: 1995
Model: Grand Cherokee
Engine: 4.0 with all of the noise and clatter
You need to find out what the signal voltage is to the PCM. If the PCM is seeing a low voltage signal due to resistance causing a voltage drop it will think the alternator needs to put out more voltage. In other words, wrong information will lead to a wrong comand. What is the CCA rating of the battery? Bigger is not always better. Battries with a high cold cranking amp rating have larger plates in order to supply those cranking amps, those larger plates displace the electrolite which kind of acts like a cooling system inside the battery. High rated CCA batteries can not take a large amp charge rate because of the lack of cooling. It will just gas the battery and make it buldge. Now that I'm thinking about it, there is a battery temp sensor under the battery tray. If that sensor is bad or giving the PCM a false reading, the PCM will keep the alternator charging too long and cause the battery to gas out. That temp sensor is there to tell the PCM how hot the battery is and the PCM will alter the charge rate accordingly. Check that sensor to see if it is damaged or unplugged.
04-12-2012, 04:28 PM
#14
Old fart with a wrench
Leave it to Busted to think outside the box! Good thinkin'! Because it's under the battery, nobody knows it's there and subject to corrosion from leaking acid. IMO, change it. It's cheaper than buying computers!
Old retired gearhead
Old retired gearhead
04-14-2012, 04:20 PM
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Year: 1993
Model: Grand Cherokee
Engine: 5.2
Lol. Ok, I feel silly... Turns out, timing was off 180! I thought comp fried out of coincidence during my motor swap. There still is a voltage problem but it runs! When I get on my laptop later I'll post a bunch of pics from during the swap. HAPPY DAYS!!! I finally have my jeep back!