High voltage

[Lead_sled]

Yesterday, my water pump went out. As the warning light came on the dash because of low coolant, my voltage light came on. Do you think it’s because the alternator got wet? Do you think it’ll go away once it completely dries? I changed the water pump today and drive down the highway and voltage would spike up to 16. I haven’t had any prior issues with voltage. With the truck turned off, an electronic meter shows the truck to be at 13.0 volts.

On a side note. I posted awhile back about my low fuel mileage. Since the truck was down, I removed the cac to have it checked. Wow, poor thing was beyond repair. Purchased a new one and installed. Just the few miles driven down the road, the truck is stronger and my wrong fuel economy meter shot up.

[Rawze]

if the alternator getting wet is causing voltage spikes.. then it is time to put a new one on. ... Voltage spikes can take out cab controllers, abs modules, and the engine ECM itself too. It is nothing to play with.

[Lead_sled]

Changed alternator, fixed problem. I guess something got shorted or bad contact when the antifreeze hit it.

[GhostHauling]

Definitely wouldn’t risk saving a dime when there’s a chance at losing 20k. I couldn’t imagine changing every single fuse and relay on a truck due to voltage spike if that’s possible but alternator is much cheeper and easier than a ECM. Did you have the old one tested ? I’m curious if it getting wet was the issue and would like to know because mine got wet when a coolant line blew but didn’t have your issue at least that I know of.

[Lead_sled]

No, didn’t bother testing it, but did keep it. Can have it rebuilt a lot cheaper than the $505 at the stealership. Maybe it was on the way out already. But was pretty evident. When the low coolant light came on, almost immediately, the voltage started going up. It went like this. Low coolant light, then red light for high voltage, then engine light letting me know the level was way down.

[Chamberpains]

(10-19-2021 )GhostHauling Wrote:  .... I couldn’t imagine changing every single fuse and relay on a truck due to voltage spike if that’s possible

I did it when I purchased my used 2010 KW T660. Took me about an hr and cost about $250 (relays aren't cheap) I'll do it again in a few years. I found a pile of tarnished and some corroded fuses, breakers and relays. I don't have ghost problems in my truck for over a year now. Weak relays are a real problem on a lot of trucks. Changing all of them on my last truck solved a lot of problems too.