73 F-250 360. I am not getting a drop in voltage after startup at the coil. On the gauges I am getting a blinking test light on the engine temp wire but gauge fails to register anything. The oil gauge wire is disconnected but old wire for it blinks and I have a SW real gauge for it so its out of the equation. Dont know about the gas gauge as I only put a 1/2 a gal in to bring the engine on line to run. This is a on frame restoration and I did put in a new ignition switch if that would make any difference to the voltage drop and gauges.

 

A '73 probably still uses the ICVR, or "instrument cluster voltage regulator", this is why the blinking light. The way they work, the little buggers have a bimetallic strip inside that heats up and makes/breaks contact every few seconds. This drops the average voltage from 12+ to maybe 5 or 6. The gauges are pretty slow to react so it works, kinda.

You want to see maybe 6 to 8 volts at RUN but you'll have to measure it at the coil when running? Has to be under load, you see, iirc. If not, then likely the resistor wire has been removed, or bypassed.

Has the points and condenser been swapped, and new coil? The voltage drop is there to reduce the current that flows through the points. They will burn up otherwise.

 

Thanks I knew the higher voltage would burn up the points with the 12 V but the coil points and cond. were put in at a rebuild and only driven a few 100 miles before I started the on frame project. Now the interior had a full make over with pristine dash parts not aftermarket but as close to NOS as ya could find, and boy the price was more then fair. I know that I should have got the blinking light on the wires( I knew but didnt know why) but why does the gauge not get the signal and move. I though maybe the new ignition switch may be the reason for no voltage drop. Any other thoughts?

 

I believe you could try grounding the sender wire(s) for Temp and Fuel (just for a few seconds or so), and see if the gauges are OK. They will quickly peg to the high side if the gauges themselves are OK.

We need to see some pictures to make accurate diagnoses too hint hint!

 

Photos are always good, what would you like photos to show.

 

Ah, just sayin' we like to see pictures of trucks.

One thing that will help, have the Shop manual? Wiring diagrams and schematics. The "pink wire" or ballast resistor wire terminates at the ignition switch. It is spliced somewhere around the firewall and goes on to the coil as a red wire.

 

This is the only type of diagram or schematic I can understand. I have wired a few of these tractors. I have Chiltons and Hayes Manuals both and the schematics may as well be in chinese 9N/2N/8N Wire Diagrams - MyTractorForum.com - The Friendliest Tractor Forum and Best Place for Tractor Information Ok on my truck when she is done I will send photos. Does this Forum have simple to understand diagrams like these for the tractors?