96 volt meter low spike

When I'm driving normal down the road everything is fine. Volt meter on the dash reads about 13 volts. When I let off the gas I get a a low spike. It runs down to about 9 volts and everything dims, headlights, dash lights, etc.
I replaced the alternator about 2 months ago so I don't think it's thst but it is a NAPA one.....

Any ideas on what could cause this?

96 burb
350
4x4

When I'm driving normal down the road everything is fine. Volt meter on the dash reads about 13 volts. When I let off the gas I get a a low spike. It runs down to about 9 volts and everything dims, headlights, dash lights, etc.
I replaced the alternator about 2 months ago so I don't think it's thst but it is a NAPA one.....

Any ideas on what could cause this?

96 burb
350
4x4


belt slipping is step one ..if so find out why ..wrong belt size is a problem ! defective belt / componets...of the belt system ..

oil leaking on belts ...etc,,,,

I have replaced both of the tension pulleys and the belt. No oil or fluids are getting on it.

Could the tension pulley spring be worn out?

I have replaced both of the tension pulleys and the belt. No oil or fluids are getting on it.

Could the tension pulley spring be worn out?


make sure you have the correct belt ..I save my OEM original belt for reference ...got new belt at auto store and they insisted it was the correct belt but it was not the correct size ! had to find belt of the correct size width/length ...then the marks on the tension pulley was correct with the correct size ...sure the spring can be bad or binding..