C2 charging problem

[Richard G.]

Re: C2 charging problem

Here is a simple diagram of a shunt electrical circuit.


It is a method of measuring current by using voltage drop. That's why it is a volt meter but measures amps.

Hope this helps.
Rick

[Noel B.]

Re: C2 charging problem

I retested the new gauge with a ground wire attached to the case. Still the needle never moves and sits at zero as I change the loading (lights on, turn signals or AC). When I measure the voltages at each terminal they are always the same. I get around 12.5 (battery voltage) with engine off and around 14.4 with engine running - same on both terminals. If I measure the voltage across the two terminals I always get zero.

In looking at the wiring diagram both of the ammeter wires end up at the horn relay connection so I guess it makes sense that the gauge sits on zero. In the past my gauge did always stay on zero while driving but would dip towards the discharge side when I turned on the lights or AC. I haven’t messed with the wires from the gauge so I don’t see what would change.

The only changes that I have made (knowingly) are replacing the alternator and the VR with a Wells 715. The charging voltage of 14.4 seems acceptable now but I can’t get the gauge to do anything.

One more thing, I read on another post that sometimes the ammeter needle slips. I took the old ammeter and reszeroed the needle. I hooked it up and it acts the same as the new one.

Sorry for taking so long on this but I am stuck. Thanks!

[Noel B.]

Re: C2 charging problem

I tested the new battery gauge with a AAA battery as suggested. I get deflection in both directions as expected so the gauge may be ok.

Also I see other posts that suggest that the gauge issue might be caused by bad firewall connections. However, if I have battery voltage on both of the wires at the ammeter doesn’t that indicate that the bulkhead connections are ok?

[Richard G.]

Re: C2 charging problem

Because the shunt circuit design even the slightest bit corrosion on a connection will affect the integrity of the circuit.
This is why they now use battery voltage meters as a charging indication instead of shunt circuits.

You should be using the low voltage setting on your voltage VOM to measure the voltage between the two wires that attach to the gauge. I typically use 5V but depending on the meter 1V setting should work. Reading typically can be in the .05 to .2V range. You saw what 1.5V does! Full deflection and the pointer hits the stops hard. For gauge testing I typically use a partially discharged battery for this reason.

If you are not getting a voltage reading, between the two gauge wires, with a load on your system something is wrong with the wiring. (The starter doesn't count) You can trouble shoot this circuit using your volt meter to look for the voltage drops in your system. It is a better method than using resistance settings. I would recommend a competent electrical shop unless you have time and are willing to go through this system over the internet. I'll help if I can.

Just for fun did you test to see if the old gauge works using the battery test?

Rick

[Noel B.]

Re: C2 charging problem

Thanks so much for your assistance. My Fluke meter is autoranging so I don’t have a 5 volt setting. However I have an old analog VOM that I loaned to my son and I can get it back. So I will proceed with checking the wiring per your suggestion. It sounds like the bulkhead connector is a likely suspect. I have looked at these connectors in the past and have been hesitant to mess with them. The 50+ year old plastic looks brittle and I am concerned that they might break when I try to disassemble them. Any suggestions on how to do this carefully - I don’t want to go backwards if I can help it...

Also I had a new starter installed recently so I suppose that the wire from the solenoid to the ammeter could be damaged. I’ll take a look.

Thanks again. I didn’t realize I was looking for such small voltage differences.

[Richard G.]

Re: C2 charging problem

Noel;
The Fluke should auto-range just fine, no need to use anything else.
You don't need to pull the bulkhead connection apart till you prove it's internally defective.
That can be done. I do not have the wiring diagram for a 1966. I believe this circuit varies over the C2 years.
Ill give troubleshooting it a try but it can get redundant and boring for others.
Might be best to take it offline and post only the solution if we get that far.

Before you do anything get a long set of leads and measure the voltage from the + terminal on the battery to both legs on the back of the gauge. Yes it is + to + voltage measurement. This should help identify which leg to go after. Might be best to mark the leads at the gauge for easy identification. Something like S=starter and R=relay. Too easy to mix them up. Might be easiest to put a spade lug on two long wire and mark the other end the same as the wiring at the gauge. They will come in handy.

"the wire from the solenoid to the ammeter could be damaged" You are reading 12V on this leg at the amp meter it is likely it will good visually.
The goal is to find the small resistance somewhere in the wiring, typically a corroded connection or damaged wire where connectors touch the connectors in the plug. If the gauge quite working when the starter was replaced it would be worth looking over carefully. Clean any paint from where the lug sets and clean and inspect the wire connection at the lug. Do the same, if you haven't already, for the other gauge wire where it terminates at the horn relay. Do all the connections at the relay as they also matter. After you do this repeat the voltage measurement from the battery to the gauge wiring. Be sure to Write it all down as good note taking is imperative. I typically use a small amount Vaseline at every connection. It keeps the air from getting to the connection and allowing corrosion. If you ever worked on a Honda most of the snap together style connections have grease in them from the factory for this same reason.
Rick

[Noel B.]

[Richard G.]

Re: C2 charging problem

Good idea on the bypass. Nothing says the gauge has to be in the interior of the car while doing so.
Yes you can contact me directly, crvtfan@comcast.net
We love Napa and Sonoma valleys. I call them Disney Land for adults.
We live in WA state, close to Portland OR.

[Noel B.]

Re: C2 charging problem

I’m on the road to recovery now. Using the bypass wires I was able to isolate the gauge problem to the wire going from the ammeter to the solenoid. With this wire bypassed the gauge works correctly. I will now determine whether its the wire itself (or connections at solenoid) or the bulkhead connector. Also with a new alternator and a Wells VR715 my charging voltage is at 14.5 V which is in the acceptable range.