1982 ISUZU I-MARK DIESEL
lights on dash lit are Battery, Fuel, Water Level. Brake. Volt meter shows about 8 volts and at times it will ease up to about 12 volts. Alternator has been replace with a known good alternator, so it seems to be either with wiring or some part. Had in shop once and they said they had traced it to the firewall where there is a relay but when they tried to bypass it it would not run. For a while it would show low charge when you started off but after a few minutes it would jump to about 14 volts by dash meter. As it is right now it is low charge when charging and heater blower doesn't work. Seems as if something is not either connecting or not kicking in and don't have a clue as to what to look for. Any help would be appreciated.