my truck had/has several problems it seems. My gauges jump all over the place with no apparent rhyme or reason, and now the gauge fuse blows all the time. When the fuse blows, the lights dim and the alternator no longer charges, along with no working gauges on the dash. at first sign of gauge prob. I replaced the alternator.
this all comes on the heels of or along with what seemed to be a hot start problem.(engine would start w/ cool water poured on inj.pump) engine seemed to not want to start, so first i check and replace fuel filter, air filter, lift pump, and oil pressure sender. still failing lift pump test, I wire lift pump to 12v source w/ inline switch, now passes lift pump test. works great for 1month, then problem comes again and batteries no longer hold a charge so I replace both batteries with same brand/cranking amp/same time mfg.
works great for 1 more month, then gauge problem starts again, now fuse blows as stated earlier.
any help/ insight would be very much appreciated

Doesn't all power run through the starter solenoid....may look there for the root of the problem...

The power to the starter is from the passenger side battery and the positive from the drivers side is connected there at the battery. Maybe the cable from drivers side to passenger side battery is bad or the spacer and connectors are bad. That would explain the starting problems. The alternator charges the batteries through the small wire that goes into the drivers side battery. A bad connection or cable will result in a weak starting battery with little help from the drivers side battery which may have a good charge, indicating no voltage problems.

The fuse may be a different problem.

Just wanted to say that I replaced the spacer between the two positive bat. cables and no more fuse blowing so far!
thanks for the advice