11.3 volts

[anthony_c]

I just finished resolving a short on fuse #3 (turn signals and gauges), but i am still showing a constant 1 volt drop on that circuit. I've done continuity tests and checked resistance on every segment that I can identify, and the problem appears to lie somewhere between Connector 3 and Fuse 3.

Otherwise, everything appears to be functioning normally. Can I safely ignore the voltage drop, or do I need to keep digging?

thanks,

tony

[Zed Head]

I didn't look at the wiring diagram but if the running lights switch is on the circuit that could be your drop. It's combined with the headlight switch, in the same box on top of the steering column. Does the top of the shell behind the steering well get hot when the lights are on?

[anthony_c]

according to the fsm the running lights should be on a different fuse, but i will check that box you mentioned.

[SteveJ]

I just finished resolving a short on fuse #3 (turn signals and gauges), but i am still showing a constant 1 volt drop on that circuit. I've done continuity tests and checked resistance on every segment that I can identify, and the problem appears to lie somewhere between Connector 3 and Fuse 3.

Otherwise, everything appears to be functioning normally. Can I safely ignore the voltage drop, or do I need to keep digging?

thanks,

tony

Where are the leads when you detect a one-volt drop?

[anthony_c]

positive lead on inbound side of the fuse socket, negative lead to ground.

- i checked several different grounding points within reach, all with the same result.

- in an effort to isolate the problem i pulled the fuse out of the socket and re-tested, no change.

- fuse 3 and fuse 4 share the same supply wire (b/w), so i pulled fuse 4 as well, still no change.

i believe the loss is coming somewhere upstream of the fuse panel, but only on this circuit. other fuses are showing 12.3v, same as the battery.

[SteveJ]

Thank you. I would think that it might be a good idea to disconnect the battery, remove the fusebox and inspect/clean it. You have corrosion that is bad enough to cause at least 9 watts of heating at that fuse. It will only get worse over time.

[Walter Moore]

The clips get loose also, which leads to arcing, which causes all sorts of issues. (Like melted fuse boxes...)

I have all of the fuse clips held shut with tie-wraps. That requires needle nose pliers, and must be done with the battery disconnected. If I was going to do it over I would just buy one of the replacement fuse boxes.

[ktm]

The clips get loose also, which leads to arcing, which causes all sorts of issues. (Like melted fuse boxes...)

I have all of the fuse clips held shut with tie-wraps. That requires needle nose pliers, and must be done with the battery disconnected. If I was going to do it over I would just buy one of the replacement fuse boxes.

There is originality and then there is functionality. If you are not anal about originality (such as a concourse car) then functionality is a primary concern. The replacement fuse box is a great first step as are Z'sondabrain headlight relays.

I was chasing a voltage drop ghost myself about 3 weeks ago that was due to a contact corrosion/oxidation issue in the combo switch for my brake lights. These cars are 40 years old and the interior components suffer from corrosion/oxidation as well.

[anthony_c]

that raises more interesting thoughts. the contacts in the back of the fuse box were shiny and showed no obvious signs of oxidation, but i'll dig into that one deeper.

[anthony_c]

following up to this thread...

after chasing false leads and cleaning connectors for a week, i've found that my missing volt returns if i disconnect the voltage regulator. is the solution as obvious as replacing the vr, or is there likely something else in play? i would keep chasing this to see where it leads, but i've not found a wiring diagram specifically for the 74 regulator.

on another note, any idea why the tach needle gives one huge bounce after turning the ign switch to "on"?

[beermanpete]

The voltage drop associated with the regulator is likely due to the field current causing VD across one of more bad connections. Check the fusible link connections, the ammeter shunt, the ignition switch, and all the connectors between the starter. Use your voltmeter to measure across each connection, switch, and fuse in the circuit. Each connection should have less than a few millivolts drop.