C2 Wiring Question - Dome Lights and Reverse Light

[hatdragracer]

All,

Got my 64 running after paint, my dome lights are not working, nor do I any longer have power to the reverse lamp connector at the firewall (Identified in my prior post) That was being used to power my electric choke!

Any way I properly connected my choke to a relay, but I still am curious why the connector lost power (my car has no reverse lights) and the dome lights work. I am sure it is yet another ground as I verified all dome lights have 12V on one of the wires, but am clueless as to where to start. The wiring diagrams give me headaches, so I would greatly appreciate some advice.

Thanks again to you who continually help me, maybe one day I will have some useful advice!

 

[Geek's 65]

Your back up light connector doesn't get power from the same circuit as your courtesy lights. Courtesy lights are hot all the time. Back up lights get power directly from the ignition switch when it's in the ON position. So your back up light connector is only hot when the ignition switch is on. Keeps you from leaving the back up lights on if you leave it in reverse with the car off. I've got a 65 with back up lights and it looks like the 12V for the back up connector also goes to run the temp guage and Parking Brake alarm light. Those still work?

Grounds shouldn't mess up this circuit. One pin is the ignition switched 12V and the other goes back to the lights or in your case to the body connector inside the car on the left. Only ground when you measure this is the one you touch with the black lead of the meter and I would guess you are using the engine (like the exhast manifold). That has to be grounded or your car wouldn't start.

Like I said, I took this from my 65 prints but I can't imagine they changed it much cause it was pretty straight forward. You are right about the prints though - they are a bear to follow sometimes. Wild Turkey normally fixes the headache that comes from prints.

Geek

 

[hatdragracer]

No the temp guage doesn't work either, good call! I thought it was the gauge. The PB alarm has never worked that I know of!

Any ideas of where to search to find why the reverse light/temp guage/PB alarm circuit is dead? Does it connect directly to the ignition switch? All the fuses are intact...any ideas would be greatly appreciated.

 

[vetzs]

Does your fuel gauge work? That also is on the same circuit as the Brake Alarm light, Temp gauge, and back up lamps. If the top fuse for these is intact (try switching with a known good fuse of the same size... top fuse in a 64) and the fuel gauge works your problem is with each item that is not functioning. If the fuse is blown see if things work with a new fuse.

After that the first thing I would check is the back up alarm, have the wires disconnected from switch under the dash or has the light bulb fallen out of it's socket, also is the light bulb good?

With the back up lights I would go under the hood and disconnect the back up light switch at the connector (area below wiper motor). I would then jump the wires going into the firewall and turn the key on with the car in reverse. If the lights come on, the switch is faulty... easy fix. If not look for bad grounds or a wiring problem.

As for the temp gauge, does it move at all when the key is turned on? If so, your gauge is fine. You may have an open in the sensor wire or a bad sensor. Have someone watch while you ground the sensor wire at the sender for an instant. If that shows a reaction on your gauge you definitly have a bad sensor. No reaction and you have either a wiring issue, (look at the sensor wire first) or a problem with the gauge.

 

[Geek's 65]

Hatdragger,

There is a black wire with pink stripe on the ignition switch. That goes to fuse #1 on the fuse block. First thing I would do is take a meter, put it in volts DC and read both sides of the fuse to see if there is 12VDC there. The key has to be ON to see that. That circuit has the Brake Alarm, Temp guage, fuel gage and back up lights (if you have them). If you have 12 VDC on both sides of the fuse, it's not the fuse. If you have it on one side and not the other - it's the fuse. Even if it looks good it's the fuse. If you don't have it on either side of the fuse, then there is a problem between the ignition switch and the fuse box.

If there isn't any voltage on fuse #1. I would take a look under the instrument panel at the ignition switch and see if you can see the black and pink wire. There are two of them that go to the same terminal. One goes direct to the ballast resistor on the firewall. The other goes to fuse #1. Here I would check to see if the 12VDC is switching to the ballast resistor just for grins. If it isn't, I think your culprit is the ignition switch or the wiring to it. If it does, I would drop the ignition switch out of the instrument panel and find a way to measure it voltage on both black and pink wires.

Let me know how you do with that. Am hoping it's a fuse that looks good and conducts bad. If the fuse and the ignition switch are OK I think the next place to peek is the fuse box. If you go there, man make sure you unhook the battery. There is power down there that is direct to the battery with no fuse inbetween and if you short that, you wind up with very crispy wiring.

Geek

 

[hatdragracer]

You guys are sharp at this stuff, the fuel gauge does not work either now that you mention it, I haven't actually driven the car yet.

The fuse looks OK, both sides check out OK, I could not locate any black/pink wires on the ignition switch.

Any idea where I can find a good pitcure schematic of the posts on the ignition switch?

 

[vetzs]

You say all the fuses are intact and check out on both sides. I assume this means you did check for voltage either with a light or VOM. If you do in fact have voltage on both sides of the fuse then your iginiton switch is working properly and the fuse is good. My guess is you have an open wire immediately after the fuse between it and where the splice is inside the loom connecting all the accessories on that circuit. Have you peeked up under the dash and lookd at the condition of the wiring? Does it look as if Bubba may have been there? If so it is definitely time for at least a new dash harness. Any repairs attempted should be as suggested in the previous post with the battery disconnected.

 

[hatdragracer]

Update, both sides of fuse was OK, but I figured out the fuse wasn't making good contact with the fuse carrier, as soon as I cleaned and reinstalled the fuse blew!

I checked the circuit and sure enough it was 0 ohms to ground, I disconnected the body connector and the wiring, the black/pink going down the connector toward the rear of the car under the driver door sill shorted to 0 ohms to ground. The other side of the body connector measured 279.4 ohms to ground at all points (Temp guage, reverse lights etc..) Why this number of ohms 279.4?..do I still have issues?

My next question where does this black/pink wire under the drivers door sill go?

I feel I am getting closer!

 

[Geek's 65]

Wow. NOW it's time for the Wild Turkey. If the 279 ohms is on the side of the fuse that drives the guages and such, then it doesn't bother me too much. What you have are three different guages and sensors (like the temperature sensor) acting like resistors in parallel to ground. Bottom line is that 270 ohms to 12 VDC is very little current draw. If it's the side that feeds the fuse from the ignition switch, it still probably doesn't bother me cause I think then you are reading throught the ballast resistor and the coil. But that zero is a mother. So first thing we need to see is which side is which.

My guess is that the side with the volts is the feed side and the other side is the short. If that's true, Reach up and disconnect the fuel guage, temp guage (if you want to cheat on this one, disconnect the sensor on the engine (green wire) and make sure the wire doesn't touch ground) and the emergency brake switch. Also make sure your back up plug isn't touching anything. See if the short is still there. If it is, then I agree that you need to find where the splice is for those and my guess is that it's in the fuse box itself. Again if you decide to play under there - unhook that battery.

Black and pink wire running under the drivers door sill. Probably to the fuel sensor in the tank. My print says that the two wires that go back there are tan and a black/pink wire.

The one comment about looking under the dash and seeing if something looks like Bubba was in there is also a good one. Bubba who wired with his toes did mine and it was a mess. (it's how I learned about where these wires went cause he really messed it up) Bubba would like to tap off of this circuit cause it was switched by the ignition. If there is a large blob of electrical tape (or scotch tape, masking tape, and let us not forget the Bubba All Time Favorite - duct tape) you might want to pick into it and see what kind of wires are going in and out of that.

Geek

 

[Geek's 65]

Guess it would be nice if I read the post you made closer. I'll drink first next time and then answer. Zero ohms and 279 ohms. The black and pink wire on the body connector going to the rear is most likely to the fuel level sensor. It should read 90 ohms. If it's reversed with the tan wire on the sensor then it could read anywhere from 90 ohms (empty tank) to 2 ohms (full tank).

279 ohm going back towards the fuze box would be OK for the reasons I had earlier. When you disconnected the body connector, did you put a fuze in #1 and see if it blew again? If it didn't, then disconnect the fuel tank sensor and see if the 0 ohms goes away. If it does, then measure the pins on the sensor and see if they really read 0 ohms. If it's still shorted then on the left side of the car back by the antenna, the harness comes from inside the car to outside through a grommet. I too had a short back there to my brake lights. There was no grommet and the wires had worn through on the body and then shorted. You may be able to feel up there and see if the harness is supported by a grommet or just hanging. If it's hanging you may or may not be able to see where the wires are shorted. If you can't see it, put a meter on the shorted wires and get it to read 0. While watching the meter (or having someone else watch the meter) reach up and move the wires around at that point and see if the reading changes.

Sorry about messing up the last one.

Geek

 

[vetzs]

Now knowing that your fuse is blowing changes things..it's definitely a short. Does the fuse still blow when you disconnect the body connector? I ask this because I suspect your problem is the fuel sender. if the fuse does not blow I would hook up the body connector then go to the fuel tank sender and pull the Black/pink 12volt lead off the sender. If the fuse still blows your short is in the wiring between the body connector and the tank sender. If the fuse does not blow it's time for a new sender. With the short taken care of you can inspect the other items on the same circuit.

 

[hatdragracer]

Geek and Vetzs, You guys rock! I followed your advice and the short was between the fuel sender and ground. I guess I will go for now without fuel level.

It was nice to hook up the battery and have everything working, dash lights, courtesy lights, and no blown fuses or smoke!

And Geek, Bubba has been here in the midwest, apparently he helped grandad install an 8-track and CB, the ball-o tape, melted (unfused) wires, and millions of taped twisted wires were scaring me, I will most likely be replacing the harness in the next couple years, I patched for now with solderless connectors.

Thanks for all your help.

 

[vetzs]

Hatdragracer, glad to see you resolved your problem. BTW I am a transplant from Wheaton Ill. Later....vetzs

 

[JohnZ]

The black/pink is the ignition-switched 12V feed to the fuel sending unit, so that was a dead short to ground, blowing the fuse. '63-'67 Corvettes (and Cadillacs of the same era) are the only GM cars that ever used that 12V-powered 3-wire sending unit; they abandoned it in '68 and reverted back to the traditional 2-wire sending unit until the advent of tank-mounted FI fuel pumps many years later.

 

[67HEAVEN]

Bubba who wired with his toes did mine and it was a mess. Geek

Great work, everyone.