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Topic: Alternator output (Read 8 times) previous topic - next topic
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Alternator output
Yahoo Message Number: 158471
I posted this question over on Techsnoz, but with the size of this group I thought to go here too...

I have searched but find no specifics about this topic. In my new '92 MB I have been doing some shakedown driving, when I noticed my instrument panel voltmeter was reading way to the high side, but still barely in "normal" range. (I have to admit I have not paid much attention to that gauge till now, working through other priorities.)

Then I put a multimeter on the chassis battery, and sure enough, it shows 14.58 V when running. The battery shows it is charged, as it should be, and the fluid level is good.

The research I've done says this is too high, and my battery may suffer, and it shows it is a good rate.  What do other LD owners see from the alternator?

Thanks
Paul
'92 Mid Bath
Re: Alternator output
Reply #1 –
Yahoo Message Number: 158478
Since you are specific about the voltage to two decimal places, I assume you are using a DVM, but to be sure, what is the make and model of the meter? Unfortunately, I'm not familiar with that vintage Ford chassis, but the dash voltmeter of our previous '83 Chevy G30 would typically read at the top of the 'normal' range. Actual battery voltage would be 14.4V or less, however. A reading of 14.58V, if real, seems a bit high, but not outrageous. With no charge to the chassis battery for 12 hrs or more, check the battery voltage - it should be under 13.0V.

Steve
2004 FL
2013 Honda Fit
Re: Alternator output
Reply #2 –
Yahoo Message Number: 158483
Thanks Steve, the meter I use is a Fluke, and checks against the Radio Shack DVM I also carry. The battery checks out just right at 12.7x V after a 12 hour rest, all electrolyte levels are fine too. I will keep an eye on the battery and check continually.
Paul
'92 Mid Bath
Re: Alternator output
Reply #3 –
Yahoo Message Number: 158484
I agree with the below and don't really see a problem with a few tenths of a volt over the 14.2 target feeding into a lead acid starting battery.

In general I've seen most manufacturers set their voltage regulators aiming for the high end of the voltage range, to make sure the battery charges even under high load when all of the electrical accessories are going (blower on high, wipers on high, headlights on, rear defrost, etc.

I suspect the voltage was checked with little electrical load on the system, and also suspect turning a couple of devices on to simulate typical driving conditions lowers the voltage to 14.2 or less.

An alternator voltage on the high side also helps with age as electrical contacts corrode, wire deteriorates, and resistance increases, lowering the voltages on the device end of the circuit.

The other possibility is that the voltage regulator is bad, but it doesn't sound like it. A failed regulator will show voltage increase with an increase in RPM and it will typically well exceed 14 volts. Seeing the voltage momentarily blip upwards and then return to "normal" with an increase in RPM is normal operation.

I'd save the worry for other things and enjoy the nice bright headlights 14V gets you.

1989 MP