alternator/voltmeter

[forbyfiev]

Hello all,
My voltmeter has been reading slightly right of vertical. It has recently started to flutter most of the time. Does this mean my voltage regulator is going bad? I'd like to replace it before I get stranded. Thanks for any help

J.B. Earl

 

[91expl-sport]

I had the same problem I went to a junk yard and there were no alt for my truck. I decided to clean the Neg and pos wire on the battery.
It turned out to a a dirty cable..Used sand paper...

 

[kvo]

JimJa -

How did you test or figured out it was the diodes. Is that the same as the voltage regulator, the square part attached to the back of the regulator with a couple wires running from it or is it on the alternator or something else?

 

[JimJa]

J.B. I had exactly the same problem last May. Turned out to be a bad diode. Because my '92 was high mileage I also replaced the alternater (~$180) and the diodes/brushes. Must admit the diodes/brushes module is flat ingenious. No disassembly is required. Two small torx screws and the entire assembly can be removed and replaced (~$50). Takes about ten minutes.

As a simplification, if you think of the charging current as being a series of three sine waves about an "X" axis, the above portion being the "charge," and below the "X" axis portion as being the "discharge," the job of the three diodes is to "cut off" that lower portion resulting in a circuit that charges. When one diode goes bad that lower portion of it's sine wave is not cut off. The result is that part of the "charge" is canceled. At idle this causes your voltmeter to "flutter." As soon as you give it a little throttle, the dominance of the two good diodes doing their job overshadows the bad one and the voltmeter smooths out. Let all three of the diodes go bad and you a figure out that the system won't charge at all. Jim.

 

[Dr.Doug]

Interesting, are you referring to the voltage regulator? I have a '91 EB. At idle, the voltage meter jumps and the lights flicker. Voltage at the battery jumps between 12.5 - 14 volts in tandem with the flickering of the dash volt meter. How much does a new voltage regulator run?

 

[kvo]

It turned out the problem I was having is pretty much what JimJa described. I had to remove the alternator to be able to remove the voltage regulator. The two diodes in the voltage regulator were worn out and they weren't making contact with the shaft. I replaced the entire unit (alternator/voltage regulator) for $149.99, bought at Pep Boys (forgot to mention, it's lifetime guarantee). Kragen Auto and Grand Auto sell the unit for $211.99. If you want to just buy the voltage regulator, it's about $50.00. If you're going to replace the voltage regulator, be careful how it's installed. The diodes are spring loaded and it was very difficult for me to re-install them.

BTW - I only saw two diodes on my voltage regulator not threee like JimJa described.

[This message has been edited by kvo (edited 11-29-1999).]

 

[S.Matsushige]

I paid $130 for both the regulator and altenator. It was a rebuilt altenator (Bosch) though which just happened to come with a year warranty as well as free towing for a year if it fails. In talking with the parts tech, a rebuilt is all new except for the casing. Ford wanted $180 for their rebuilt and it came with no warranty and regulator had to be purchased separatly (rip-off if you ask me). The regulator was an easy install due to a pin which held the brushes in place until the installation. Once the regulator is installed you pull the pin and it releases the brushes on to the shaft. Alot easier than I thought it would be. When I suspected my altenator was failing, I removed it and had it tested at a local parts shop for free.

 

[forbyfiev]

Thanks everyone for your responses.

I had my mechanic check the voltage reg one day and when i went to pick it up he had already ordered a new alternator. He said mine was shot and showed me where the brushes had worn down grooves in the alternator.
My voltmeter still reads wrong, though

J.B.

 

[forbyfiev]

P.S.
actually the voltmeter doesn't flutter as much, but it still reads high.
We're now talking about a possible bad ground in the system.

J.B.