RLR

I am looking at buying a 99 with about 100k miles on it and the only thing I can’t explain is that sometime the voltage will drop in to the negative when it starts... OK, sounds like the intake heaters right? But then when you start to drive it, it stutters a little then it will start to pick back up and runs great!

The owner says it started to do it after he put in some Optima batteries in.
Do you think the heaters are drawing too much power and the batteries can’t supply the voltage needed?
Maybe an alternator?

John Faughn

Not sure about the negative part , in less they changed the gauge , no neg. position on gauge ?
Is it worded wrong , when it start the gauge goes neg. ?
How cold is it there , how long before it pickup ? should be with in a few seconds with a little throttle , about 900 RPM .
Check fuel pressure ?
There has been some reports that the Optima's have had issues the last yr. or so , do a load test on the batteries & alt.

Erik@LCD

i agree, charge and then load test the batteries with them disconnected from the truck.

neveragain

When the heaters are cycling they are apparently drawing about 220 amps so figure that is about 2600 watts of heat for the engine, yes it will make everything work. Do let the engine warmup (gauge needle starts to rise) before you drive it. Let it sit for 3/5 mins before you shut it off.