Disconnecting negative terminal for alternator change
01-08-21, 03:25 PM
#1
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Disconnecting negative terminal for alternator change
The official tech docs says to disconnect the negative terminal of battery before beginning removing the alternator. Is it because when you remove the positive connection from the alternator, it has a high risk of touching the body ground and if negative isn't disconnected that will cause a short between the two battery terminals? Is my understanding correct? Is their a particular reason you need to disconnect negative and not positive?
01-08-21, 04:04 PM
#2
Yes, if the positive touches any part of the chassis... something will fry. However, when you disconnect the battery (if you aren't using an OBD memory saver) you'll likely lose some emissions settings and saved memory settings. That's really the only downside.
I have SOMETIMES wrapped the positive lead in heavy cloth/plastic on other cars if there was enough space to work around the cable, but disconnecting the battery is easiest/safest.
The car uses a NEGATIVE ground (like most all cars nowadays)... so when you disconnect that, the positive has nowhere to go/nothing to do. You could kind of disconnect the Positive too and leave the neg attached, but then in theory you still have a "live" ground that if anything electric or anything with a charge touches the chassis, you could create a short.
I have SOMETIMES wrapped the positive lead in heavy cloth/plastic on other cars if there was enough space to work around the cable, but disconnecting the battery is easiest/safest.
The car uses a NEGATIVE ground (like most all cars nowadays)... so when you disconnect that, the positive has nowhere to go/nothing to do. You could kind of disconnect the Positive too and leave the neg attached, but then in theory you still have a "live" ground that if anything electric or anything with a charge touches the chassis, you could create a short.
The following users liked this post:
lexus-is2 (01-08-21)
01-08-21, 08:40 PM
#3
Yes, if the positive touches any part of the chassis... something will fry. However, when you disconnect the battery (if you aren't using an OBD memory saver) you'll likely lose some emissions settings and saved memory settings. That's really the only downside.
I have SOMETIMES wrapped the positive lead in heavy cloth/plastic on other cars if there was enough space to work around the cable, but disconnecting the battery is easiest/safest.
The car uses a NEGATIVE ground (like most all cars nowadays)... so when you disconnect that, the positive has nowhere to go/nothing to do. You could kind of disconnect the Positive too and leave the neg attached, but then in theory you still have a "live" ground that if anything electric or anything with a charge touches the chassis, you could create a short.
I have SOMETIMES wrapped the positive lead in heavy cloth/plastic on other cars if there was enough space to work around the cable, but disconnecting the battery is easiest/safest.
The car uses a NEGATIVE ground (like most all cars nowadays)... so when you disconnect that, the positive has nowhere to go/nothing to do. You could kind of disconnect the Positive too and leave the neg attached, but then in theory you still have a "live" ground that if anything electric or anything with a charge touches the chassis, you could create a short.
It's also part of jumping a car that has you connecting the Negative last on the dead cars engine block vs either battery as hydrogen is explosive!
The following 2 users liked this post by 2013FSport:
GrizzlyMan (03-21-21),
lexus-is2 (01-09-21)
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