2000 SLS Voltage Problem

2011 Views 8 Replies 4 Participants Last post by mlprus, Apr 1, 2009

mlprus

Discussion Starter · Apr 1, 2009

O.k. to start off the battery in my 2000 sls kept getting weak, so I'd charge it overnight on 2 amp charge and it'd be fine for a few days then get weak again. I checked the voltage on the DIC and it would say 11.8 volts, no matter what, running, not running, idle, open throttle, didn't matter. So after reading some of the posts on here about charging and voltage problems, I changed the alternator. I got the car back together about an hour ago and still the same voltage, 11.8. Both times (before change and after change) I read the voltage with a volt/ohm meter. Reads the same as the DIC. Very frustrated. My question is, what else could the problem be? PCM? The old alternator was faulty by the way, only 11 volts on a bench test. The new alternator tested 14 volts on the bench. Very confused, please help.

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Submariner409

· #2 · Apr 1, 2009

PCM has nothing to do with charging voltage/amperage. You need to trace and clean every battery cable connection. Your charging/normal highway voltage should be between 14.2 - 15.2 volts. Fully charged battery voltage, disconnected for 4 hours, is 12.6 volts. You have no practical way of measuring charging amperage.........A similar problem was traced to a poor ground connection at the (under the rear seat ???) frame connector.

11.8 sounds suspiciously like the loaded battery voltage reading, so maybe there's a bad field voltage connection which is not exciting the voltage regulator (inside the alternator). More connector checks in order........

What happens when you start the car, bring the idle up to 1200 rpm, and turn everything on ???

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Ranger

· #3 · Apr 1, 2009

I think you should have started by changing the battery.

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mlprus

Discussion Starter · #4 · Apr 1, 2009 (Edited)

When I start the car and hold at about 1200 rpm and turn everything on the voltage drops from 11.8 to 11.4, it did not raise after I turned off all electrical stuff. I can't see the alt. being bad though, fresh reman, bench tested at 14-15 volts at the starter shop? I actually did swap out the battery for a fully charged one out of my other car that had a good alt. that was before I swapped the alt. on the caddy. My apologies.

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mlprus

Discussion Starter · #5 · Apr 1, 2009

Oh, and I've noticed my power locks acting funny. Locking and unlocking as they please.

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Ranger

· #6 · Apr 1, 2009

Have you pulled the DTC's?

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iowasevillests

· #7 · Apr 1, 2009

Back to what sub said, have you traced down the battery cables from the battery to see the state of the connections, ie. are they corroded, loose, frayed etc. I would pop the cables off, clean them very well with a stiff wire brush, put them back on and hit them with battery terminal spray to prevent corrosion from developing in the future. This won't remove the possibility of a bad connection, but it will at least lower it.

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mlprus

Discussion Starter · #8 · Apr 1, 2009

Yep. H for history, C for current.
B1004 H, B1009 H, B1271 H, B1327 H, B1340 C(new one still not here, shipped wrong one), B1652 H, B2220 H, B2221 H, B2242 H, B2243 H. (I don't even have a memory seat switch)

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mlprus

Discussion Starter · #9 · Apr 1, 2009

The reading with the multimeter was pulled from the jump start location on the strut tower/inner fender, fuse box.

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