I documented my MTV 3116 water pump change.

[RRaulston]

Might be some useful info for someone. I did run into some interesting things. FYI, I'm not promoting this. I get paid ZERO. I have benefitted from others videos and feel it's my responsibility to add my fair share. Thx RR

MTV LMTV CAT 3116 Water Pump Change (youtube.com)

 

[GeneralDisorder]

Your confusing electrical readings (5v, dropping to 4.5v) after disconnecting the 12v are probably capacitors discharging from electronics. Had you waiting a bit I bet it would have dropped to zero. Things like the voltage regulator on the alternator likely have internal capacitors that don't immediately drain. One thing you can do on vehicles is disconnect both the positive and negative battery terminals and touch them together to discharge the various capacitors - or turn on the lights. On the later A1 trucks with the battery disconnect relay and the LBCD it is important to note that the LBCD has HUGE capacitors in it that will hold quite the charge in them assuming they are good. You can actually turn on the lights on the truck for several seconds with the batteries completely disconnected if they are good and charged. Something you NEED to be aware of on later 3126b and C7 trucks.

 

[RRaulston]

Your confusing electrical readings (5v, dropping to 4.5v) after disconnecting the 12v are probably capacitors discharging from electronics. Had you waiting a bit I bet it would have dropped to zero. Things like the voltage regulator on the alternator likely have internal capacitors that don't immediately drain. One thing you can do on vehicles is disconnect both the positive and negative battery terminals and touch them together to discharge the various capacitors - or turn on the lights. On the later A1 trucks with the battery disconnect relay and the LBCD it is important to note that the LBCD has HUGE capacitors in it that will hold quite the charge in them assuming they are good. You can actually turn on the lights on the truck for several seconds with the batteries completely disconnected if they are good and charged. Something you NEED to be aware of on later 3126b and C7 trucks.

Thats interesting about the capacitors. I always thought my disconnect switch cut all power to the truck. It appears it only cuts half..? Oh well, zero drips on the new pump. I thought the price was reasonable for a genuine CAT part as well..

 

[GeneralDisorder]

Thats interesting about the capacitors. I always thought my disconnect switch cut all power to the truck. It appears it only cuts half..? Oh well, zero drips on the new pump. I thought the price was reasonable for a genuine CAT part as well..

The FMTV disconnect switches that I've worked with do cut both the 12v and the 24v positive leads.