My 98 12v is giving me some fits. When i bought it. Fuel and oil pressure gauge come on and off when they want too. Now speed and tach arent working. Neither is odometer. Its been stuck at 182193 for a while now. But my volt and temp gauges work... last week my truck died on me. Got two new batteries, truck started. Took it in for alt. Meter test while truck was running. Test came back, 12.19 low reg. Good diodes. they said take alt. Off cause they needed to test just it and i did and the alt. Passed tests 11 times. So i bought a new one anyways. Mounted it. Drove my truck to work. 60ish mile drive. Went to leave. Truck wouldnt even turn over. So i jumped it. It drove all the way home. But i had no eletrical working. No lights, gauges, nothing... i put a volt meter tested on driver side batterry. Just under 12v without load with load under 8v same readings on passenger batt. When my truck is running without anything on. Volt meter on gauge reads around 12v when i turn anything on it drop to 8v instanitly. Please help me out guys

 

Sounds like the Alternator is putting out Noise .. you can get a noise filter .. thet will keep things ( ECM, TCU) from freeking out ..

Have the Alt. load tested if you can .. and charge and load test your batteries as well...

Keep us posted