[yragat]

I have a chevy one wire alternator--it always read 14 volts---today it dropped to 12--should I replace alternator?

all wires correct and tight

[sqzbox]

Anything less that 14 V is shot. Might want to get it tested at the local part's store just to be sure. AZ and advance will test it for free. That will eliminate the gauge being faulty. At 12V it won't be long before the battery will give out stranding you on the road or parking lot away from home. Right now it appears your running off battery voltage only.

[yragat]

I checked it with voltmeter at alternator and its reading 13-14 volts. NOW GET THIS!!! I had a B&M Megashifter that had a back-up light switch on it--this past winter I changed to a Gennie shifter which did not have the back-up light switch---so I taped the wires up and thought hell I never use the back-up lights anyway. But just yesterday I thought since I live in Pa I should have a way to turn them on because if the lights are on the car they must be functional. I put them on a toggle switch . Tonite the wife and I went out for a fish sandwich and somehow she (or her big purse must have hit the toggle (yeh its on her side of the car) because when I walked around the car I noticed the lights were on---turned them off and everything OK now---can't believe them 2 bulbs would pull that much juice---think I'll dissconect them again!

[sqzbox]

LOL. Never leave controls within reach of a woman! Just move the switch.
I have a toggle switch on my 4x4 with a red light in-line and the auxilary light's mounted backwards on the roll bar. Never had working back-up light's since I bought the truck. The auxilary light's work better than any back up's like having headlight's on the rear. Works great when 4 wheelin' in the dark.

[yragat]

I know what U R saying---raced flat fenderer Jeeps with BIG motors for years---and plenty of trail riding after dark

[T-bucket23]

If you put the backup lights back on does your voltage drop to 12. In a healthy electrical system a pair of backup lights will not effect the alternator output.
What is the output voltage with the headlights on.

I am betting your regulator int the 1 wire is failing.

[Rickracer]

Could be a poor ground to the Voltmeter too,

[yragat]

It stays right around 14 with headlights AND elec fan running---They are both run thru relays,but backup lights arent---wonder if thats why????

[T-bucket23]

Originally Posted by yragat

It stays right around 14 with headlights AND elec fan running---They are both run thru relays,but backup lights arent---wonder if thats why????

They draw the same if they are run straight or through a relay. The relay just takes the big load off the switch.
Did you try turning them back on to see if the problem comes back. I am still not convinced that the backup lights are adding enough load to pull alternator voltage down to 12 volts.
Makes no sense

[Rickracer]

Originally Posted by T-bucket23

... I am still not convinced that the backup lights are adding enough load to pull alternator voltage down to 12 volts.
Makes no sense

I agree, hence the comment about a poor ground. When I run into stuff that doesn't make any sense, about 98.9% of the time, it's a result of a poor ground.

[yragat]

Ran it all day yesterday---14 volts came home turned on backup lights just fol the hell of it and sure enough--right down to 12---weird huh

[Rickracer]

Did you check the output at the alternator while the dash gauge was reading that low? I would........

[yragat]

Originally Posted by Rickracer

Did you check the output at the alternator while the dash gauge was reading that low? I would........

No I didn't---I will tomorrow