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Your CLK/LTR/CTSY 20A fuse also powers the power door lock circuit.
You may see power on both sides of the dome lamp "IF" you are checking voltage with either door open OR if your headlight switch is full CCW.
Dash Lights,
You will ONLY see voltage at the INST 5A LPS fuse when the headlight switch is pulled in the park or head position as this is the rheostat portion of the headlight switch.
I don't know what electrical guide you ordered...
Most are generic Chevrolet Line diagrams for 1st design only.
IMO this is the best electrical troubleshooting manual for the 78 Corvette Specific that covers both 1st & 2nd design...
You can find them on e-bay
Your CLK/LTR/CTSY 20A fuse also powers the power door lock circuit.
You may see power on both sides of the dome lamp "IF" you are checking voltage with either door open OR if your headlight switch is full CCW.
Dash Lights,
You will ONLY see voltage at the INST 5A LPS fuse when the headlight switch is pulled in the park or head position as this is the rheostat portion of the headlight switch.
I don't know what electrical guide you ordered...
Most are generic Chevrolet Line diagrams for 1st design only.
IMO this is the best electrical troubleshooting manual for the 78 Corvette Specific that covers both 1st & 2nd design...
You can find them on e-bay
This is the one I ordered. I checked another corvette here and only have power on one side of dome light with 1 or both doors open? I did check the 20A clk fuse power on both in and out
From: South of Phoenix Arizona, but North of no-where.
Did you get a free wiring diagram from here? This is fantastic and printable. I made up a few for different systems (so not confusing) and filled in the wiring colors with colored pens.
There are a few colors that are different on the car and a couple rather confusing areas but once you get studying it sorts out.
my 81 is basically a large bowl of spaghetti but this really helped me get quite a few things in order.
Did you get a free wiring diagram from here? This is fantastic and printable. I made up a few for different systems (so not confusing) and filled in the wiring colors with colored pens.
There are a few colors that are different on the car and a couple rather confusing areas but once you get studying it sorts out.
my 81 is basically a large bowl of spaghetti but this really helped me get quite a few things in order.
From: South of Phoenix Arizona, but North of no-where.
WIRING DIAGRAMS
Just look up above in the index above or below your post ( Forums- c3/ general - electrical
“free wiring diagrams “ for info.
or as a last resort
try. phillipchidester@gmail.com
Last edited by Redbirdman; Apr 19, 2022 at 08:55 PM.
Here is the Line Diagram for a 78 from Willcox Corvette LINK: http://repairs.willcoxcorvette.com/w...e-this-one.png
Copy and paste into a MS paint or other and save...
78-82 Power Door Lock circuits were nearly identical with the exception of Early 78 used the BAT cell in fuse panel as the power source, Late 78 Main Dash (IP) harness had provisional connectors built in for the door lock harnesses.
Also, the switch wire colors and Circuit Numbers on the 78 both early and late are different from linked drawing below.
Circuit 194 on the linked drawing is circuit 900 on the 78 and is a Purple Wire.
Circuit 195 on the linked drawing is Circuit 901 on the 78 and is a Pink Wire.
The wire colors and circuit numbers are the same from the switch to door actuators.
Door Lock Link: http://repairs.willcoxcorvette.com/w...-schematic.png
And No,
The Anti Theft Relay Coil does use Circuit 140 as source, it is only linked by S140 (S=Splice) Late build only...
Straying from your Power Door Lock Problem...
But I do understand "if" in fact you are working on a early 1978.
Several provisional options "MAY" have been powered and connected together by that single BAT socket (cell) in the fuse panel.
Post a photo of your fuse panel...
Your first photo shows a part number 344813 that would be the Horn Relay.
Not sure the area of where your second photo was taken but assume general area was behind the Speedo/Tachometer.
Look for a part number on that Orange item. If it is 463498 that would be your Courtesy Light Delay Timer.
Also if that is your delay timer, and it is in the general area behind Speedo/Tachometer you are for sure working on a Early 78.
Along with other changes to the (IP) harness between early and late 78 one of them was a location change of the delay timer to behind the glove box.
The Willcox Line Diagram I posted a link to above is a good drawing of a Early 78.
Or you can wait for the Troubleshooting Manual you said you ordered...
Straying from your Power Door Lock Problem...
But I do understand "if" in fact you are working on a early 1978.
Several provisional options "MAY" have been powered and connected together by that single BAT socket (cell) in the fuse panel.
Post a photo of your fuse panel...
Your first photo shows a part number 344813 that would be the Horn Relay.
Not sure the area of where your second photo was taken but assume general area was behind the Speedo/Tachometer.
Look for a part number on that Orange item. If it is 463498 that would be your Courtesy Light Delay Timer.
Also if that is your delay timer, and it is in the general area behind Speedo/Tachometer you are for sure working on a Early 78.
Along with other changes to the (IP) harness between early and late 78 one of them was a location change of the delay timer to behind the glove box.
The Willcox Line Diagram I posted a link to above is a good drawing of a Early 78.
Or you can wait for the Troubleshooting Manual you said you ordered...
Location is below the instrument cluster.
I decided to run a fresh wire from the batt terminal on the fuse box to the orange wire in the harness. Locks work as well as the courtesy lights now. Thanks for all the replies and help. I truly appreciate it!
78 Electrical Issues
