switch under the battery

lewvan

New member
After removing the battery from my 1998 Grand Cherokee, I found what appears to be a pressure switch in the bottom of the battery bracket. Anyone know what this switch does? If it is to detect the presence or absence of the battery, where does it get its energy to indicate anything if the battery is gone. If it is part of the security system, what happens when I replace the battery? The reason I removed the battery and detached the bracket was to gain better access to the alternator.
 

It is a battery temp sensor. If the battery is hot, based on the sensor reading, the PCM reduces the charge voltage so the battery is not damaged. You will see the effects when you comparing alternator charge voltages on cool days vs days in the high 90's while wheeling. Normallyn14.4V vs more like 13.8 or less.

You need the sensor or your will throw a code and your battery may not get charged while driving.
 
new question. Are there any components inside the black molded plastic connector that attaches the rotator wire to the alternator. It has two ring connectors that go the the alternator shell and two smaller flat connectors that connect to the rotator terminals. Denso alt. 98 chrerokee
 

Yep, it is the battery temperature sensor. It changes the charge rate based on the temperature of the batttery.
 
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