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Doctor Olds
I Need A Remedy For What's Ailing Me.
Premium,VIP
join:2001-04-19
1970 442 W30
kudos:18
reply to theboz1419

Re: Resetting ECM-ECU on old car - helpful?

said by theboz1419:

In fact when I took my car in to get a new battery, the old 7 year old battery still was able to get a good reading on a battery tester, and was around 13.5 volts.

No 12V Automotive starting battery is 13.5 volts. That is the alternator output, not the battery. A 12 volt battery that is new or in good condition is 12.6 volts (2.1 volts per cell) when fully charged.



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What’s the point of owning a supercar if you can’t scare yourself stupid from time to time?


Vchat20
Landing is the REAL challenge
Premium
join:2003-09-16
Columbus, OH
reply to Juggernaut
said by Juggernaut:

said by theboz1419:

All a battery is used for is to start the car.

That's incorrect. A battery is also a power buffer, and used to supply a stable voltage, and current. Alternators fluctuate as demand from the battery is needed, or exceeded.

This. And with pretty much all cars since around ~2000 or so having a lot of engine functions electronically controlled, a weak battery and forcing these systems to rely more on the alternator can cause all kinds of issues. And for most vehicles if they sense a low battery voltage, they will adjust the alternator output accordingly to try and recover which can also exacerbate things.

As a personal anecdote, my mom's prior vehicle, a 2000 Durango, had some strange issues at one point especially concerning staying running after starting. It would crank and start fine with no struggle but after a second or so would outright die unless you kept the revs up and even then it would struggle some. Mind you this was with the 4.7L engine which was the first in the model to go to a distributorless ignition (ie: Coil-on-pack, driven directly by the ECU). Long story made short it was narrowed down to a combination of a weak battery and battery clamps deteriorated greatly (possibly causing the weak battery issue). After the clamps and battery were replaced, the problems completely vanished from that point forward.
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I swear, some people should have pace-makers installed to free up the resources. Breathing and heart beat taxes their whole system, all of their brain cells wasted on life support.-two bit brains, and the second bit is wasted on parity! ~head_spaz