wierd alternator problem

[miles]

hi guys my 89 2.9 bII has a strange problem once it warms up and the RPM drops to about 800 the alt. gauge drops to the discharge side. so i thought i'll try my alt out of my 88 2.9 ranger which works fine in the ranger once in the bII that alt.seems to be worse than the original. i reinstalled the original alt and right back the same issue the stanger part of all this is that i had tfi trouble on the weekend and cranked that engine over for three days trying to get it to fire with no battery charger the battery remained strong. so i was wondering are those alt. gauges prone to go bad thanks any opinion apreciated.

 

[martin]

All factory gauges in all vehicles are crap. You might get different results from one vehicle to another due to differences in pulley sizes etc. If the alternator is supplying higher than battery voltage it's usually working.

 

[miles]

thanks i"ll check it out and reply as soon as i can.

 

[miles]

hi guys sorry for the slow responce but i did check the voltage at the battery today under full load high beams and defroster on high. I still got 13 volts at the battery so i guess the gauge is out to lunch thanks guys !