After I start my Rodeo, three dummy lights remain lit for a few minutes: 1) low fuel indicator, 2) brake system and 3) charging system. After a few minutes of driving, they all turn off at the same time. It's always just these three lights. While they are on, the A/C fan doesn't work. Other than that, the truck seems to run normal. Any ideas what causes this? Maybe my almost new alternator is going bad?

Definate charging system issue. Your charging system needs to maintain ~14VDC with the truck running. Any more/less will cause the conditions you describe. A bad aftermarket/reman. alternator is usually the cause. Have to go OEM with alternators on the 3.2/3.5 isuzu's, especially with auto trans. Or you'll be changing them out every few months :banghead: .
G/luck
Joel

You are absolutely right. I didn't notice it before, but the voltmeter drops to 10 volts when the conditions occur. This is at idle right after the truck is started. After driving a few blocks the voltage goes up to 14 volts and all is well.

Well, I took the Rodeo to Pep Boys where I bought the alternator. They say it tested out fine. I talked to the mechanic myself. Alternator was good, battery good, connections good, etc. They saw the low voltage but couldn't figure it out. Charged me $20 for the diagnostics and told me to go to a shop that specializes in electrical problems.