1966 Corvette convertible rear compartment light

[Joe T.]

Re: 1966 Corvette convertible rear compartment light

Looking at that removed section of the harness....

What's really strange is it appears the PINK wire is bare. Somewhere in that melted bundle is the ORANGE, which is the Power to the compartment lamp. Both PINK(fused power to the Fuel Sender via IGN = ON), and ORANGE(also fused, constant power), somehow survived the meltdown without blowing either fuses. Something caused the meltdown.

Was the rear harness underneath the wire cover below the carpet? Did it appear to be rubbing the bare metal of the cover? Was the rear harness replaced during the restoration?

Just out of curiosity, try to separate those melted wires. I'd suspect the ORANGE or the WHITE wire is open circuit. If the PINK melted and was shorted to WHITE(GND), it may have opened the WHITE wire and possibly melted elsewhere too. My concern would be the integrity of the rest of the harness where it traverses back to the rear lamps, etc.

Your localized repair looks good, but as suggested, I would be inclined to replace that entire rear harness.

Rich

Attached is a photo of the separated wires. As you can see the orange wire is separated.

[Richard M.]

Re: 1966 Corvette convertible rear compartment light

Joe, Great detective work to find root cause. Yes the Orange wire was open circuit which is why there was no power to the lamp socket. Why that area of the harness is the area the short occurred is mysterious.

I would suspect that at some time someone may have installed the wrong bulb, a single contact base type, which shorted Power and Ground and blew the fuse. Possible that they installed higher rated fuse until the wire melted. In the process, the short eventually started to melt the adjacent wires in the bundle including the Pink, etc.

After they figured out they had the wrong bulb, they probably then installed the correct #90 bulb but it was too late.

However, I just checked the fuse for this circuit. It's the "CLK LTR CTSY HAZ" fuse at the bottom position in the Fuse Panel. Its spec is 20 AMP. That's a lot of current to allow to pass to the rear lamp socket before blowing. I'm wondering if a wrong bulb was installed would it in fact blow a 20 Amp fuse before the long length of wire to the rear compartment would begin to overheat. If a 30 Amp fuse was installed, I'd say that small gauge wire(IIRC 18G) would open before the fuse. Yes, best check that fuse for a 20A.

Edit...
The above fuse is for a '67. The lower fuse on a '66 is "COURTESY STOP LPS" I think that is also a 20A fuse but need to check.

Edit again...
Conflicting data on the fuse. Photos of 1966 panels show 15A there, but another reference from the owners manual states 20A. Confused.


Rich

[Joe T.]

Re: 1966 Corvette convertible rear compartment light

I go along with your theory. Just pulled the fuse. It is a 32 volt 20 amp. The panel does show 15 amps. I agree with some different literature showing different data. Would it be wise to go to a 15 amp or stay with the 20?

[Richard M.]

Re: 1966 Corvette convertible rear compartment light

I go along with your theory. Just pulled the fuse. It is a 32 volt 20 amp. The panel does show 15 amps. I agree with some different literature showing different data. Would it be wise to go to a 15 amp or stay with the 20?

Interesting... Just when I think I have these electrical systems figured out, new questions come to mind. Why would the fuse panel show 15A and the owners manual specify 20A?

Then I thought about it more, but it makes no sense to me for 1966. In 1966, Backup Lamps were standard, therefore the 2 inner tail lamps, which were Stop Lamps in earlier years(without optional BU lamps), required more total current for the circuit. The BU Lamps are on a different circuit, IGN Pink. Since a 1966 only has 2 Stop Lamps I'd think a 15A would be adequate, but maybe not.

That circuit has these loads:
Clock
Glove Box Lamp
3 Courtesy Lamps
Stop Lamps(Outer only)

Maybe there is a TSB instructing to replace the 15A with a 20A in that circuit or a AIM notation in UPC 12 at a certain date to replace the 15A with a 20A? I don't have a 1966 AIM.

I suppose it's possible that if all circuit items were loaded simultaneously that 15A wasn't enough. If the doors were open activating all 3 courtesy lamps, glove box open, the brake pedal pushed, AND the clock was wound down and triggered the wind-up solenoid all at the same time, how much current would be drawn in that circuit? Maybe close to or more than 15A?

I'd suggest you replace that 20A with a 15A and load the circuit as above and see what happens. If your clock has been converted to Quartz that would reduce the original load spec. If original clock that would match original load spec.

If you have a Ammeter setting in you Multimeter it'd be interesting to put it in series with that circuit fuse to get a actual measurement.

If you decide to go with a 15A remember the built in safety "telltale": If your Courtesy lights go out due to a blown fuse, you now don't have Stop Lamps.... a safety issue while driving.

Rich

[Joe T.]

Re: 1966 Corvette convertible rear compartment light

Interesting... Just when I think I have these electrical systems figured out, new questions come to mind. Why would the fuse panel show 15A and the owners manual specify 20A?

Then I thought about it more, but it makes no sense to me for 1966. In 1966, Backup Lamps were standard, therefore the 2 inner tail lamps, which were Stop Lamps in earlier years(without optional BU lamps), required more total current for the circuit. The BU Lamps are on a different circuit, IGN Pink. Since a 1966 only has 2 Stop Lamps I'd think a 15A would be adequate, but maybe not.

That circuit has these loads:
Clock
Glove Box Lamp
3 Courtesy Lamps
Stop Lamps(Outer only)

Maybe there is a TSB instructing to replace the 15A with a 20A in that circuit or a AIM notation in UPC 12 at a certain date to replace the 15A with a 20A? I don't have a 1966 AIM.

I suppose it's possible that if all circuit items were loaded simultaneously that 15A wasn't enough. If the doors were open activating all 3 courtesy lamps, glove box open, the brake pedal pushed, AND the clock was wound down and triggered the wind-up solenoid all at the same time, how much current would be drawn in that circuit? Maybe close to or more than 15A?

I'd suggest you replace that 20A with a 15A and load the circuit as above and see what happens. If your clock has been converted to Quartz that would reduce the original load spec. If original clock that would match original load spec.

If you have a Ammeter setting in you Multimeter it'd be interesting to put it in series with that circuit fuse to get a actual measurement.

If you decide to go with a 15A remember the built in safety "telltale": If your Courtesy lights go out due to a blown fuse, you now don't have Stop Lamps.... a safety issue while driving.

Rich

I pulled the 20 amp fuse and installed a 15 amp. Everything works fine without blowing the fuse.. Can't take an amp check on the circuit. My meter goes to 10 amps max. Will leave the 15 in. Going to pull the other fuses. Looks like this guy put in a box of 20 amp fuses in. Some people take the easy way out. Thank you again for steering me straight.

[Richard M.]

Re: 1966 Corvette convertible rear compartment light

Joe, Probably keep some spare 20A fuses in the car also just in case you need them.

For reference, I am still confused at the discrepancy regarding this fuse. Below is the 1966 AIM UPC 12 page showing St Louis instructions to install a Part# 120151 Item#5 fuse which cross references to a 15A AGC fuse. More data shows the AMA spec specifies a 15A fuse at that location. (PDF page 57 HERE)

Also is a First Ed 1966 Owners Manual page showing that fuse location as 20A (Ref part# 106653). Also note the artists drawing of the Fuse Panel. It is silkscreened 20A. This is contradictory to actual samples of original 1966 fuse pabels which show it silscreened as 15A. Also note the errors in the descriptions of some of the fuse circuits:

"Stop, License, Courtesy". The License lamp is NOT on this circuit(Orange).
"Tail and Backup Lamps". These are 2 separate circuits.....
"Tail" comes from the Headlamp switch Brown fused circuit, which also powers License lamp(2nd fuse from bottom in the panel).
"Backup Lamps" from IGN Pink circuit.(top fuse in the panel)

Also to avoid possible future confusion, I researched the RPO V74 Hazard Lamps option again. It is not part of the ORANGE Courtesy Lamp circuit. Its power source(Orange wire with female plug terminal) plugs directly into the fuse panel BAT PWR WDWS terminal, which is unfused.

Photos courtesy Rich Mauser.

[Joe T.]

Re: 1966 Corvette convertible rear compartment light

I totally agree with you on the discrepancy. The 15 amp fuse is holding up with everything on in that circuit.. I will keep it in unless it blows. Thanks again for your knowledge and help.