Over Voltage (16v) problem and the possible solution (1 Viewer)

[KillerBox]

In case this helps anyone in the future.

Before I purchased my 1 owner 2001 LX, the service records state they replaced the alternator with a Factory refurbished alternator about 20,000 miles ago. I don’t know what their problem was.

As soon as I purchased my 2001 LX, I replaced that alternator that was working 100% with a high output 250 amp DC Power alternator because I upgraded the stereo system.

After about 3 months, my high output alternator started putting out 16 volts. So I put the factory alternator back on the LX and sent the high output alternator back in for service.

When the high output alternator came back about 6 months ago, I placed it back on the LX.

Last night it was raining & when I started the LX, all my dash lights were on again and the alternator was showing 16 volts again (even while running the AC full blast and all the headlights).

I thought that it would be highly unlikely that two alternators would do the same thing. So I wanted to check my battery connections, alternator sensor fuse on the fuse block on the positive battery post (I think it is 7.5a) and then my last resort was to check the alternator itself.

The battery connections were tight and the factory ground was great. So my next step with the engine turned off, I sprayed some DeOxIt electrical cleaning spray (the weaker type of DeOxIt made for gold connections) into the alternator sensor fuse block. Restarted the LX and my alternator instantaneous went back to working perfectly and putting out 14 volts no matter what I had turned off or on.

So my guess is that my problem the first time was this sensor fuse connection too. So now, I am thinking about putting some dielectric grease in the fuse connection so maybe this will not happen again.

 

[gatormark91]

16V @ 250 amps = 0.64 ohm resistance
14V @ 250 amps = 0.56 ohm resistance

So anything that increases or decreases the resistance of the circuit (ie, a bad connection, corrosion) can cause the voltage to be read differently. (Not an electrical engineer, just my take on the above). If it happens again, measure resistance across the connection with your meter before you do anything to fix, then measure it after. I'd expect you would see a difference.

 

[KillerBox]

16V @ 250 amps = 0.64 ohm resistance
14V @ 250 amps = 0.56 ohm resistance

So anything that increases or decreases the resistance of the circuit (ie, a bad connection, corrosion) can cause the voltage to be read differently. (Not an electrical engineer, just my take on the above). If it happens again, measure resistance across the connection with your meter before you do anything to fix, then measure it after. I'd expect you would see a difference.

If you don't mind me asking, measure where? With the fuse installed, fuse itself or the fuse connections with the fuse removed?

 

[gatormark91]

If you don't mind me asking, measure where? With the fuse installed, fuse itself or the fuse connections with the fuse removed?

You'd have to trace some wiring to find a spot where you could test without cutting anything. Don't remove anything, you are testing resistance and continuity. But it sounds like you found the problem without having to do that just by tracing the problem away from the alt.

 

[sean2202]

First start at the alternator connection. The large wire that comes off of it. This wire in this connection can corrode over time leading to all sorts of light/charging issues. If that is OK then work to the fuses.
On fuse boxes and connections, I clean them with wd-40 and then apply dielectric grease.

 

[erse]

@KillerBox are you still running the DC power alternator? Any further issues? trying to decide if thats the way to go and whether to get 180 or 250 version