battery temp sensor lost?? - JeepForum.com
 
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post #1 of 11 Old 06-07-2019, 05:44 AM Thread Starter
matthew123
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battery temp sensor lost??

98 grand cherokee with 2.5 diesel.

When its warm outside or when engine warms up alternator charges around 13.4 volts, so im guessing its the battery temp sensor. I have taken the battery tray out but theres no sign of sensor or any wires that should attach to it.. or maybe it doesn't have one at all? also just changed the alternator with no change.
Would be great if anyone could tell me where to look next.

And i have a 2001 cherokee where that sensor is in its own place and fine.

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post #2 of 11 Old 06-09-2019, 08:48 AM
xtrattitude4u
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No, there's no temp sensor for the battery.
The alternator will be more efficient in cold temps, and less efficient in warm temps.

My alt does 14.5 in the cold, about 13.7 in the warm.

It is normal.

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post #3 of 11 Old 06-09-2019, 11:06 AM Thread Starter
matthew123
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13.4 would be kinda medium, goes down even more and now it wont seem to really go to 14 anymore, was better at winter..
I have to charge the battery quite often with charger so i wouldn't stay on the side of the road every time i stop.
I have already changed the battery maybe 2 months ago with known good one and i don't wont to buy new one unless i know it will be charged correctly.
On my Cherokee (XJ) it was charged always at 14+ and never had any problems.
just a thought, what if i disconnect 2 small wires behind the alt and leave only positive wire. The VR is in the alt will it be fine or kill the system?
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post #4 of 11 Old 06-09-2019, 01:25 PM
kg6mov
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Uh, there is a temp sensor for the battery, and it would matter.

The voltage regulator is part of the PCM.


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post #5 of 11 Old 06-09-2019, 01:27 PM
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Quote:
Originally Posted by xtrattitude4u View Post
No, there's no temp sensor for the battery.
Incorrect, there is a battery temp sensor that attaches to the bottom of the battery tray. It makes a pretty decent change in the alternator output voltage depending on the battery/ underhood temperature.


At 25C (75-80F) the temp sensor should have a resistance of around 9k-11k ohms, so if the wire harness is there but not the harness connector & temp sensor, solder a suitable resistor between the two wires. Other option is to install a suitable potentiometer to vary the resistance for the "sweet spot".
The colder it is, the higher the output voltage baseline is. I honestly can't remember what the resistance should be for ie. 0C.

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post #6 of 11 Old 06-09-2019, 01:34 PM
xtrattitude4u
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Crap I'm sorry, didn't mean to misinform.
I am learning something today!

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post #7 of 11 Old 06-09-2019, 08:52 PM
firebane
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I forgot to plug my battery temp sensor in and I couldn't figure out the weird voltage going on as it was always around 13.6v .. once I plugged it in back up to a good 14.4 volts.


They did say DIESEL, so maybe it doesn't have one?
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post #8 of 11 Old 06-11-2019, 11:46 AM
jeepjeepster
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Does the diesel have it in the same place?

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post #9 of 11 Old 06-11-2019, 11:50 AM
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Does the diesel have it in the same place?

Yeap, it's under the battery tray.

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***Under construction***
1990 XJ (4-door), 4.0 I6, AW4, NP242, PBR 42" tires, Unimog 404 portal axles, 110" WB, full cage + uniframe completely rebuilt, front 3-link + panhard / double triangulated 4-link rear,... ***SOLD***
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post #10 of 11 Old 06-11-2019, 03:15 PM
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The issue mine had with a bad battery temp sensor was that the voltage gauge would peg occasionally to max. Changed it, no more problem.
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post #11 of 11 Old 06-13-2019, 02:13 AM Thread Starter
matthew123
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There is a hole under the battery tray for it but no sensor or wires. If someone have the same engine maybe could post a picture where it should connect to wiring harness? As i have searched most of the engine bay for it.
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