battery gauge/power surges

'85 760TURBO · Post by **'85 760TURBO** » 04 Dec 2005, 11:47

my battery post and wires have been forming corrosion off and on for a few weeks. i had the battery tested and it showed it was fine, and i cleaned the post and wires and put new ends on the wiring. it still had corrosion on the ends after about a week, and the battery gauge would occasionally surge, the needle going from about the half way point all the way over to the red and back, depending on how fast the car was going(it surged higher when going faster) today i bought a new battery and recleaned everything, and the gauge is still moving as i drive. not as bad, the needle doesn't get as high as before but still moves with accelerration of the car and the lights and fan motor also "surge". anybody know what the deuce is going on? is it the alternator? loose/bad wiring somewhere i can't see?

Guest · Post by **Guest** » 05 Dec 2005, 18:38

measure the voltage

with the car sitting (not running) the battery should read about 12v

with the car running you shoud get 13.7v-14.3v

when you first start the car the alternator will charge at a high rate for a few minutes

When you turn on a heavy load you (headlights) you may notice a slight dip

I put wheel bearing grease on the battery terminals after I have cleaned and tightened them. They are nasty to touch but they do not corrode.

I am not sure if I have answered your questions

'85 760T · Post by **'85 760T** » 12 Dec 2005, 12:03

i bought a new battery, the other one was leaking around the post and the cells. it showed it was putting out what it should, but the leaks couldn't be a good thing. with a new battery and new tight connections i've had no more surges.

LaRy · Post by **LaRy** » 14 Dec 2005, 10:51

Guest here has given some good advices how to check the voltage during different situations. It is actually the charging regulator that should take care of this. Maybe you need a new one. The regualtor is most probably assembled together with the alternator brushes and bad brushes will make the alternator work bad, it could definitely be overcharging.

Guest · Post by **Guest** » 23 Dec 2005, 18:07

I have a similar problem in my 1986 740 volvo, except that the battery gauge would move from the middle of the range where it used to be, down to the red. It does this when I am driving at about the same speed. It is like if something gets stuck, then losens, then stuck again. The alternator warning light works fine, because it comes red when I start the car, then it stays off. It would flicker sometime when I idle slow.
I wonder if it is the battery, the regulator, or the whole alternator.
My regulator is an integral part of the alternator and has the electrical connection that is supposed to go to the "battery temperature sensor". The sensor is nowhere to be found. Maybe it never had one, maybe I lost it. The connector where the sensor is supposed to connect to is hanging in front of the battery, and the wiring to the regulator show normal continuity. If the sensor is a must-have, then that may explain why the regulator would not work fine.
And Merry Christmas all