1964 Electrical Issue

[Patrick H.]

Hi All,

I'm helping to prepare a 64 for our Regional. We're running into an issue with the electrical system and I'm not sure if it is related to the wiring, a switch, or both.

Using the headlight switch, we can get the front running lights and the headlights to work. We cannot get the dash lights or the rear taillights to work via the headlight switch. We have tried 3 different headlight switches and even rebuilt one, but no change. I find it hard to believe that 3 switches are wrong. We've tested them and it seems like there should be an external jumper to connect the two internal halves of the headlight switch.

If we remove the headlight switch and run a jumper from the hot red wire to the correct wires (brown for rear, dark green for dash lights) we can get those lights to work.

Any ideas?

Patrick

[Michael H.]

Re: 1964 Electrical Issue

I think the inst lamps/tail lights circuit has it's own fuse??

[Wayne M.]

Re: 1964 Electrical Issue

If we remove the headlight switch and run a jumper from the hot red wire to the correct wires (brown for rear, dark green for dash lights) we can get those lights to work. Patrick

Patrick -- I think Michael H. is on the right track to the solution for your problem. Let me give a little more detail on what I THINK is happening, as I've been down this same path in the last month, and it turned out that by messing around with +B jumpers, I blew the 10 amp Tail Lamps fuse.

I'm assuming you're using a "131" headlamp switch or equivalent. Now I've never had one of these puppies apart, but after studying the circuit diagram and using an ohmeter on the switch contacts, I've found that this switch is divided into 2 parts, with a "firewall" between the 12 gauge red which serves headlamps (= black w/blue stripe 20B/LBL); parking lamps (= purple 20PPL), and the second switch action on the 18 Ga brown feed (18BRN) which comes from the downstream side of the Tail Lamps fuse. The fact that the latter works when you jumper from the 12R proves that the 18BRN is not providing current from the fuse.

The Tail Lamps and the Stop Lamps and Courtesy Lamp 15 amp fuse are fed both by a single 14R that junctions to a 12R that comes through the firewall plug from the horn relay bus. The same junction is where the 12R headlight feed originates (not fused).

Now here's the interesting part (at least to me). Why should the tail lamps fuse affect the panel lights ? Well that's because the 18BRN from the Tail Lamps fuse (input to the headlight switch) feeds the dark green (16DG putput from the switch) which feeds into the Panel Lights 4 amp fuse. So the panel lamps fuse can be intact, yet if the tail lamps fuse is blown, then there's no current to the panel lights, either. In other words, the panel lamps are doubly protected, as the current for this service flows through 2 fuses.

Hope this is clear as mud --- bottom line; check the tail lamps fuse .

[Michael H.]

Re: 1964 Electrical Issue

Yup, what he said. AND, if the brake lights work, that automatically means the bar in the bulkhead connector is hot so the problem is from the fuse forward. (probably the fuse or corrosion in the clips for the fuse)

[Ray G.]

Re: 1964 Electrical Issue

Hello Patrick;
Echo previous posts.
Additionally the dash/panel lamps do not work when the tail lights are out to inform the driver of the problem.
Hope that helps.
Ray

[Wayne M.]

Re: 1964 Electrical Issue

Hello Patrick;
Echo previous posts.
Additionally the dash/panel lamps do not work when the tail lights are out to inform the driver of the problem.
Hope that helps.
Ray

Ray -- and another sign; when the clock stops, it's probably a sign the brake light fuse is blown.

I wonder if all this was by design ?

[Patrick H.]

Re: 1964 Electrical Issue

OK, Thanks for the tips.

As an addendum, when trying to figure this all out, we have already removed all fuses, replaced all fuses with new ones of the correct amperage, and cleaned all fuse holders. In addition, we removed and cleaned the bulkhead connector. That was before trying 3 switches and rebuilding one of them.

However, if I'm reading you right, the issue is still in the CIRCUIT of the tail and dash panel lights even though we can jumper them and get them to work? If one bulb is not operating correctly would that cause this to happen, as we're also having an issue with the bulb sockets (diagnosed when we jumpered the headlight switch).

Does the fact that we can jumper them help anyone to narrow it down? Electrical issues are my least favorite.

[Wayne M.]

Re: 1964 Electrical Issue

... if I'm reading you right, the issue is still in the CIRCUIT of the tail and dash panel lights even though we can jumper them and get them to work? If one bulb is not operating correctly would that cause this to happen, as we're also having an issue with the bulb sockets (diagnosed when we jumpered the headlight switch).

Does the fact that we can jumper them help anyone to narrow it down? Electrical issues are my least favorite.

Patrick -- if one or more bulbs is not operating (due to local socket problems) that should not affect the apparent headlight switch problem.

Now, I assume you are 'jumper'ing from the multi connector that plugs into the top of the headlight switch. You have tried the red (12R) hot feed (which the switch uses for the headlights and parking lights) and all is good. This shows that your firewall 12R connection is good (so all the other stuff like radio, wipers, heater blower, ignition etc should work).

Next suggestion: try, with the same black headlight switch connector, to use the larger brown wire 18BRN which should also be a hot feed (verify 12 volts with light probe or voltmeter) coming from the outlet of the tail lamps fuse, (not the smaller 20BRN wire, which is switch outlet to the tail lamps, and which you have already verified as OK). Use the 18BRN to jumper to the 20BRN (tail lamps should light). Then jumper 18BRN to the dark green 16DG (the panel lights should work). All this with the HL switch pulled 1 or 2 notches, of course .

If all this works, incredible as it seems, the 3 light switches you've tried may each be defective. If something doesn't work jumpering from the 18BRN, we can take it to the next step.

[Patrick H.]

Re: 1964 Electrical Issue

Patrick -- if one or more bulbs is not operating (due to local socket problems) that should not affect the apparent headlight switch problem.

Now, I assume you are 'jumper'ing from the multi connector that plugs into the top of the headlight switch. You have tried the red (12R) hot feed (which the switch uses for the headlights and parking lights) and all is good. This shows that your firewall 12R connection is good (so all the other stuff like radio, wipers, heater blower, ignition etc should work).

Next suggestion: try, with the same black headlight switch connector, to use the larger brown wire 18BRN which should also be a hot feed (verify 12 volts with light probe or voltmeter) coming from the outlet of the tail lamps fuse, (not the smaller 20BRN wire, which is switch outlet to the tail lamps, and which you have already verified as OK). Use the 18BRN to jumper to the 20BRN (tail lamps should light). Then jumper 18BRN to the dark green 16DG (the panel lights should work). All this with the HL switch pulled 1 or 2 notches, of course .

If all this works, incredible as it seems, the 3 light switches you've tried may each be defective. If something doesn't work jumpering from the 18BRN, we can take it to the next step.

We checked the 18 brown wire, and it is not hot at the switch connection.
However, the second fuse from the bottom (taillights) is hot on both sides.

Patrick

[William C.]

Re: 1964 Electrical Issue

the fuse being hot on both sides means the fuse is good, but does not verify connection bettween the fuse and the fuse holder terminal. I beleive that is where you will find your problem, good old rust will get in there and keep the connection from being made. The other alternative would be a broken wire, much less likely. Get the fire on the wire at your 18 brown in the hdlp switch connector and you should be working fine. Both of the lower fuses in the block are fed by the same feed, so the problem is at the inboard end.

[Patrick H.]

Re: 1964 Electrical Issue

the fuse being hot on both sides means the fuse is good, but does not verify connection bettween the fuse and the fuse holder terminal. I beleive that is where you will find your problem, good old rust will get in there and keep the connection from being made. The other alternative would be a broken wire, much less likely. Get the fire on the wire at your 18 brown in the hdlp switch connector and you should be working fine. Both of the lower fuses in the block are fed by the same feed, so the problem is at the inboard end.

Clup,

Where do I physically find the "fuse holder terminal"? Are you just meaning the clip that holds the fuse? Or something on the back side of the fuse block? The owner removed all fuses and cleaned the clips, but should we look in back?

Patrick

[Wayne M.]

Re: 1964 Electrical Issue

Clup,

Where do I physically find the "fuse holder terminal"? Are you just meaning the clip that holds the fuse? Or something on the back side of the fuse block? The owner removed all fuses and cleaned the clips, but should we look in back? Patrick

At least you're narrowing it down. Yes, with your probe, touch the edge of the right side CLIP on the 2nd from bottom fuse (not the metal fuse barrel end). This will tell you if the fuse-to-contact connection is good. Otherwise, it's in the 18BRN wiriing from the fusebox to the HL switch connector.

Here's a crop of an excellent shot of the inards of a C2 fusebox. Got it from Corvette Forum (believe originator was 427Nassau or similar username). Note 10 or 12 red feeding both bottom fuses. Also see 18BRN wire on the left side of fuse, just above orange wire (everything's backwards, remember). Maybe customer dislodged something when cleaning, or you've got corrosion on the backside of the box.

[William C.]

Re: 1964 Electrical Issue

Wayne's answer is spot on, I should add, that in the 60's, those terminals were silver plated for conductivity, not so much to worry about on the 10 amp circuits, but the 20 amp and larger fuses generate a LOT of heat. I don't know how the owner "cleaned" the fuse clips (Terminals) but a second look might be in order. Note that the 18 Brown is attached directly to the back of the fuseclip, and that connection can be another source of problems if the fuseblock has seen salt air and subsequent corrosion.

[Patrick H.]

Re: 1964 Electrical Issue

OK.

I think the owner is out there today checking the back of the fuse box for corrosion. He was going to remove all the fuses again and attempt to be thorough. I'll post an update later.

Patrick

[Patrick H.]

Re: 1964 Electrical Issue

Update:

It was corrosion on the back of the fuse box.
The owner cleaned it up today, and all the lights now work just fine.

Thanks for the help, everyone!

Patrick