Truck now won't run

[GMCNUT]

Hey guys - I have a weird situation. My 64 2500 series had a bad gas guage so I decided to remove it yesterday and replace it with another one I removed from a spare cluster. To get the dash out, I had to unhook the two large guage wires coming to the aftermarket Ammeter that was put into my cluster back in the 60's. When I disconnected these two wires the insulation was so old it just broke and fell into the floorboard in a million little pieces - revealing the bare twisted copper which would cause a major problem, so I decided to replace these large wires and remove them entirely from the truck for the time being. So I disconnected the positive terminal on the battery, and proceeded to remove these wires. Once pulled back through the firewall, I went to see where they were attached, and one of them went to the positive post on the starter, and the other was attached to the voltage regulator wiring coming down the pass side inner fender to the starter - it was attached in a big bundle of tape on these wires so I simply snipped it off a couple inches from the taped area and did the same for the one going to the starter. I capped the two short remaining wires w/ wire nuts for the time being. So I completed the re-install of the dash cluster with nothing else messed with aside from this ammeter wiring removal, and re-connected the newly cleaned cable terminal to the also cleaned pos terminal on the battery and hit the ignition switch. Dead. pulled on the headlights and nothing. No power to the dash or ignition. Since the ammeter was aftermarket and added I cannot imagine what in the world that could have to do with the trucks ability to start - does anyone have a hypothesis to share as to why removing the ammeter wiring would have caused this? The only other wiring messed with was the unplugging and replugging of the main harness behind the cluster, and I made sure to re-plug it correctly and not in any different clockwise or counterclockwise position. Aside from that I cannot imagine why this truck is not getting power. I have not tried crossing out the starter with a screwdriver to see if power from the battery is getting to the starter yet, but I feel quite sure it is since the battery is known to be hot and was absolutely working perfectly prior to this guage service project....anyone got ideas on this?

[raycow]

The ammeter measures ALL the current going into or out of the battery except for the current which spins the starter. When you removed the ammeter, you effectively cut off all power to the rest of the truck. To run without it, you must connect (to each other) the cut ends of the wires which formerly connected to the ammeter. This needs to be done with fairly heavy wire, say about 10 gauge. A non-shunt ammeter such as you have is the ONLY dash gauge which works this way. Don't try it with anything else.

Ray

[GMCDAC]

Originally Posted by GMCNUT

Hey guys - I have a weird situation. My 64 2500 series had a bad gas guage so I decided to remove it yesterday and replace it with another one I removed from a spare cluster. To get the dash out, I had to unhook the two large guage wires coming to the aftermarket Ammeter that was put into my cluster back in the 60's. When I disconnected these two wires the insulation was so old it just broke and fell into the floorboard in a million little pieces - revealing the bare twisted copper which would cause a major problem, so I decided to replace these large wires and remove them entirely from the truck for the time being. So I disconnected the positive terminal on the battery, and proceeded to remove these wires. Once pulled back through the firewall, I went to see where they were attached, and one of them went to the positive post on the starter, and the other was attached to the voltage regulator wiring coming down the pass side inner fender to the starter - it was attached in a big bundle of tape on these wires so I simply snipped it off a couple inches from the taped area and did the same for the one going to the starter. I capped the two short remaining wires w/ wire nuts for the time being. So I completed the re-install of the dash cluster with nothing else messed with aside from this ammeter wiring removal, and re-connected the newly cleaned cable terminal to the also cleaned pos terminal on the battery and hit the ignition switch. Dead. pulled on the headlights and nothing. No power to the dash or ignition. Since the ammeter was aftermarket and added I cannot imagine what in the world that could have to do with the trucks ability to start - does anyone have a hypothesis to share as to why removing the ammeter wiring would have caused this? The only other wiring messed with was the unplugging and replugging of the main harness behind the cluster, and I made sure to re-plug it correctly and not in any different clockwise or counterclockwise position. Aside from that I cannot imagine why this truck is not getting power. I have not tried crossing out the starter with a screwdriver to see if power from the battery is getting to the starter yet, but I feel quite sure it is since the battery is known to be hot and was absolutely working perfectly prior to this guage service project....anyone got ideas on this?

I'm sure if you do what Ray said you will get it running again. I just wanted to say I dig what's in your GMC collection! Would love to see pics of all of them!

Later---DAC

[jbstcu]

Hey there! I'm brand new in here, but so excited to finally be at home!
I'm no expert, just used to messing with wires. I second the recommendation, although I'd try to remove the stub from the positive post altogether, run a new one from that side to the stub you snipped on the side going to the voltage regulator of the starter. This will effectively remove "junk wire" where possible and complete the recommended solution as previously stated. The ammeter is just a measuring tool effectively completing your circuit. Do, when you remove it, you need to close the circuit back somehow, as explained now. Hopefully that explains the logic and next time you remove a "measuring instrument" you'll be good to go all on your own! But certainly we're always here for questions too. Happy wiring friend!

I know I'll need tons more help than this as I dive into my first rebuild, and I'll be humbly reminded of how much more I don't know than what I do know! Ha! Let us know how it goes!
-Grace and peace,
James.

[GMCNUT]

Guys, thank you for the advice - I went back to work on the truck and I noticed that one of the snipped off heavy guage wires was in a sizeable taped up bundle on the regulator wiring, so when I undid that tape, it revealed the factory ring terminal on the large Red wire coming from the voltage regulator - the dealer had simply bolted another ring terminal to this one and taped it up - so when I cut the wires, I did cut any power from the regulator to the starter. So best part is, no factory wiring was butchered which was my worry - I simply removed the Ammeters ring terminal and reattached the factory one and presto - instantly working again. Thank you for the advice - you guys were dead on!

[jbstcu]

Awesom! Keep truckin' ...