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Discussion Starter #1
So the alternator failed in my 1988 F150, 5.0l, 4x4, 5 spd. I had it tested and the rectifier had failed. I ended up just getting a new (reman) 2G alternator instead of doing the swap to a 3G. After completing the install I started the truck and used my multi-meter to check the voltage at the battery. It was a steady 14.8V with no load and 14.6V with the lights on and blower on high. All seemed good.

The next day I drove the truck and it was dark and cold, so the lights and blower were on. I noticed the volt meter in the dash was only showing about 12.5V, or so. If I turned the fan down all the way, the meter would rise above 13V.

I do need to check the voltage at the battery with my multi-meter again, but what other problems might I have for the new alternator to perform this poorly in such a short time?
 

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Don't trust the OEM gauge.
 

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Where does the sense wire that the regulator uses to monitor system voltage connect to?
 

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Discussion Starter #4
Where does the sense wire that the regulator uses to monitor system voltage connect to?
Everything connects to where it did before. I installed the new BBS plug that comes with the alternator and installed a new regulator plug because I broke the original plug trying to disconnect it. I'll have time to check the voltage at the battery tonight, so I'll have a better idea if the dash volt meter is reading correctly.
 

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The Y/W wire is the sense wire. I had a similar problem with my 3G. Moving the sense wire to the battery terminal corrected it. In your case, maybe there is some kind of unwanted resistance in the new plug.
 

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Discussion Starter #6
I just tested the system with my multi-meter on the battery and with the blower on high and headlights on the meter was reading 14.8V. I did not drive it, or let it run long enough to get up to full operating temp, but it was idling at 750, or so, RPM. The dash gauge was was showing the 13.5V, so it would seem that it is a little off. I'll have to check again if it drops after driving for a while, but maybe it is nothing to worry about.
 
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