I'm having issues with the headlight switch as well as the rear brake lights, but first I have to say that the wiring has been cut about a bit because we are not allowed indicators to act as stop lights, so my back up lights are now indicators and the other lights are stop and tail.
All the indicators work as they should including the hazards, what I don't have are stop and tail lights or dash lights. I'm sure the stop lights is just something to do with the brake light switch at the pedal so not worried about that one.
I have been using a Haynes manual for the wiring diagrams but to be honest they are not the best to follow, I also have the assembly manual but that assumes you have in tact wiring harnesses.
I did a quick engine refresh and since putting the engine back in these items do not work so think I might have missed something or broken something.
I spent all of the last two days trying to sort this out, I bought a new headlight switch from Rockauto (which will fit but does not have the vacuum ports for the headlight actuation, so I stripped out the old and new switches to make one good one with the vacuum log), however the same result no dash lights, no tail lights.
I did a continuity test on the switch and all works but when I put the wiring to the switch the Orange wire has 12volts as does the red wire, but as soon as I pull the switch to turn on the side lights the Orange wire reads next to zero and the brown wire that should lead to the rear tail lights reads next to nothing as well.
I have been upside down in the footwell of this car for two days and I'm close to setting it on fire!!!! I think someone at GM must have been having a laugh when they decided to locate the fuse box where they have, has to be the most stupid of places ever on a vehicle.
So unless anyone has any ideas of what to test my next question is has anybody completely rewired their C3 using a painless or rebel wiring kit, I'm getting so close to ripping it all out.
Oh and there is this yellow wire in the engine bay near the alternator that I have no idea where that goes either.

 

That yellow wire goes to the alarm horn mounted on the firewall below the brake booster. VERY common for it to be disconnected due to false alarms.

 

Excellent, that is one out the way then as there is no alarm on this vehicle.

 

Up date time.
I managed to sort out the brake lights as it was as I suspected something to do with the brake light switch, one of the wires was cut somewhere when I was replacing the steering column.
The headlight switch was an altogether different story and to be brutally honest I'm still not sure what it was that eventually got the side lights to work. I fitted the new switch and they didn't work, I messed with the old switch, still no go, I swapped bits from one switch to another, still not working.
In the end I went right back to basic's and put power directly off the battery to the side light wire and they worked, so still thinking the switch. The switch actually has three power feeds to it, (I originally thought only two), one for the side lights, one for the dash and dimmer system and another for the headlights. All three had twelve volts going to the switch but when I pulled the switch to the side light position the side light power went to milli volts instead of a constant 12 volts, this is what I wasn't able to comprehend, eventually I pulled and prodded every single plug wire I could find up under the dash until one of the plugs I was pulling and pushing started to activate and deactivate a relay in the centre console area, eventually I pushed and pulled so much that the activating and deactivating stopped and suddenly I had all the side lights working.
I have no idea which plug it was, but after a week the lights are still functioning as they should so I will leave well alone now, just happy they work as it got very close to ripping the whole cars wiring out and putting in an EZ wire or similar complete wiring system in it.
Still have a few other wiring gremlins but slowly getting there and it is at least useable as is.

 

The relay you heard in the center console area was almost certainly the alarm relay. You should disconnect it because it is a very frequent cause of battery rundown! It's located just ahead of the shifter with many of the wires leading into it blue or blue striped. Don't mistake it with the nearby (but significantly larger) pulse windshield wiper module/relay. Such was an option but a very popular one as it came with the "convenience group" in 80% or so of '79s. The alarm system was standard.

 

Thanks for the info, I will remove the plug from that relay as you suggest as I don't have the alarm horns or basically anything else that was to do with the alarm (was there meant to be a key switch somewhere?). I think that when it was imported, whoever did the wiring mods for the UK standard lights removed and cut various wires that linked to all sorts. For an example the interior light only comes on when the light switch is fully rotated and not when you open or close a door, there are extra horns (four by my last count, and not any of them musical, just plain old horns) why? The wires to the wiper motor are all cut with just one that makes the wipers work but at only one speed, even the supply to the distributor has been cut and reconnected for some reason.
They had even bridged out the clutch pedal inhibitor switch, only found that out after a few years, when one day the car would not start, no click or anything from the starter motor, took ages before I found the bridging wire had come away, plugged it back in and off it went. I might add that when I replaced the brake servo (pig of a job) I found all the bits still in the footwell behind the carpet to now have the inhibitor switch work as it was supposed to do.
I'm not bothered about an alarm, as the exhaust is so loud (my doing) that it would act as an alarm anyway.
Don't shoot me for this but I really don't care about originality on this car, I just want to drive it and have fun.
Again thanks for the information, it is appreciated.

 

The switch to arm and disarm the system is attached to the driver side door key cylinder. Even with the horn removed the system can go in to alarm mode which operates that relay and drains the battery.

 

My Haynes manual states that the theft device is connected to a key but not that that was the door lock key so that sort of stumped me to start with. I have never been able to leave the battery connected for a long time without using the car each day, so I have disconnected the relay but left the battery connected. I will see how long it will survive without me having to jump start it. If it lasts a week I'll be happy.

 

Hayne's manuals are too general to be of much use with C3s. Earlier C3 models had separate alarm arm/disarm key locks located in various places.

 

Get yourself a laminated poster size print of the wiring diagram for your car. I have one for my 79 and it hangs on the wall right next to the car. I believe it's Lectric Limited who makes the poster and I think all the vendors have it. I bought mine at Corvettes at Carlisle years back.

 

I will see if I can obtain the laminated wiring diagram for the future as I do know there are still loads of cut and wrong coloured wires all over the vehicle, for example the wiper motor has just one wire poking out of the area that the terminal block would be on the motor and the wiper switch has been bypassed, never really bothered me as there was a switch just under the steering column that you switched on and the wipers worked, however, I am trying to get it to a more driver friendly vehicle so getting the original switch to operate the wipers would be useful at some point.

As to starting, I left the vehicle for about 5 days with the battery connected and the alarm relay disconnected and it turned over fast enough to put fuel in the carb and start after about the sixth revolution of the engine, so that is looking promising as I'm sure that it used to drain the battery by about day 5 beforehand. Will see what happens for a longer period as I am in the process of rubbing down and painting the front nose at the moment so will not be starting or driving it for a little while. If it hasn't drained the battery by the time I have it back together that will really be a bonus.

 

If you see a single pink wire coming out of the wiper motor cover don't bother it. It is part of the wiper delay system and is no longer produced. In '79 delay wipers were part of the extremely popular "convenience group" option that included the underhood light, courtesy lamp delay, delay wipers, lighted passenger vanity mirror and perhaps another thing or two I've forgotten. With the exception of the special wiper motor cover all of the parts for the wipers are available in reproduction. I've visited the UK numerous times and even for a "fair weather car" working wipers seem an absolute must have

The big laminated wiring diagram is useful but I suggest you buy a 1979 Corvette Service Manual as it is truly model specific and has circuit-by-circuit schematics and descriptions. Earlier C3s had no specific manual and were included in the general manual that covered all Chevrolet models.

 

Yes wipers are useful over here no matter what the season. My wipers do have the intermittent option on them, but I can't ever remember having used that feature, they have either been on or off.
I will look for a year specific manual, I have the haynes manual as stated before, plus another C3 generic one and the 79 assembly manual.
Thank for everyone's help it is much appreciated.

 

1979 Corvette Repair Shop Manual Original

 

drwet, thanks for the link, at least I know what I need to look for, unfortunately they will not deliver to the UK, I will need to find something over here or off evilbay or one of the corvette parts suppliers.

 

I hadn't started the motor in well over two weeks but today I needed to move it so, turned the key and it cranked over maybe 4 times, I then stopped cranking, pressed the throttle to the floor and released it then cranked again and it fired up nice and easy. This is with me leaving the battery connected since the last time I used it so it looks like by removing the security relay plug the battery holds it's own, which is a big plus for me. Didn't even know that the vehicle had an alarm in the first place, secondly it has never worked (even the horns were not connected up), so not having the relay connected doesn't bother me in the slightest, having the battery keep a charge is vastly more important.

 

Great to know that it's keeping the charge. Many "new" owners are not aware of the factory alarm system until it sounds constantly (almost always a problem with the switches around the driver door key cylinder) or it drains the battery because the previous owner simply disconnected the dedicated alarm horn (to stop the noise) without disconnecting the relay (to stop the current draw).

 

Free wiring diagram link...

https://www.corvetteforum.com/forums...or-anyone.html

 

SwampeastMike, I have owned my C3 for the best part of 15 years but it never occurred to me that there would have been an alarm system on the vehicle as most cars over here at that age didn't have them either. It is definitely a case of a previous owner had disconnected the horns for the alarm prior to my ownership, without disconnecting the relay. I posted before about the yellow wire that should have gone to the horns, it was originally just taped up out of the way and when I did some work I found it.
Redvette2, Thanks for the link, I have sent him a message along with my email address and asked if he is still able to send them out, I'll keep you posted.

 

I see this thread going on for awhile with many great suggestions...like Swampy's. Here's another:

These are the ticket...forget the Haynes, and the shop manual iterations...get the color-coded which are much easier to troubleshoot. Get the "best tools" available like these laminated, colored-coded wiring schematics and you'll avoid the drama of using imperfect 1970s wiring schematics. Working with the right tools always makes the task less complicated but still requires patience. The free stuff sucks as well.