New 1977 Wiring Problem
Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 828
Likes: 2
New 1977 Wiring Problem
Hi All,
I have a few circuts really messed up in my 77. I know in most other cars a solid black wire is a ground. I have found that I have quite a few black wires that have juice. I do not think this is correct.
The bottom black wire on my wiper motor has juice, I think that should be a ground. Am I right here?
I need to fix the interior light, the A/C-Heat & fan motor & the wipers.
There was a bit of splicing under my hood. I have a few live wires that are open and not taped and not factory.
Is a light under the hood stock or an add on?
Thanks
Jack
I have a few circuts really messed up in my 77. I know in most other cars a solid black wire is a ground. I have found that I have quite a few black wires that have juice. I do not think this is correct.
The bottom black wire on my wiper motor has juice, I think that should be a ground. Am I right here?
I need to fix the interior light, the A/C-Heat & fan motor & the wipers.
There was a bit of splicing under my hood. I have a few live wires that are open and not taped and not factory.
Is a light under the hood stock or an add on?
Thanks
Jack
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
Check fuses, rotating the round fuses can make a good connection.
Yes, there was a factory light under the hood.
Yellow wire to wiper should have power w/ key on.
Black should be gnd.
Yes, there was a factory light under the hood.
Yellow wire to wiper should have power w/ key on.
Black should be gnd.
Instructor
Joined: Mar 2008
Posts: 173
Likes: 1
From: New york New york
Try this
Hi All,
I have a few circuts really messed up in my 77. I know in most other cars a solid black wire is a ground. I have found that I have quite a few black wires that have juice. I do not think this is correct.
The bottom black wire on my wiper motor has juice, I think that should be a ground. Am I right here?
I need to fix the interior light, the A/C-Heat & fan motor & the wipers.
There was a bit of splicing under my hood. I have a few live wires that are open and not taped and not factory.
Is a light under the hood stock or an add on?
Thanks
Jack
I have a few circuts really messed up in my 77. I know in most other cars a solid black wire is a ground. I have found that I have quite a few black wires that have juice. I do not think this is correct.
The bottom black wire on my wiper motor has juice, I think that should be a ground. Am I right here?
I need to fix the interior light, the A/C-Heat & fan motor & the wipers.
There was a bit of splicing under my hood. I have a few live wires that are open and not taped and not factory.
Is a light under the hood stock or an add on?
Thanks
Jack
Go get an inexpensive low voltage continunity tester,turn every thing off then check from grnd to chasis or motor chances are you will be o.k. now check each one to a hot lead or install afuse and connect to batt.pos. should be hot. keep in mind that resistance can allso be a problem.
P.S. please tape off all bare wire's both pos, or neg the last thing you need is a burnt harness
JRL
Le Mans Master
Joined: Aug 2006
Posts: 7,423
Likes: 1,558
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
On my 74 there is a three prong connector at the wiper motor and a seperate black wire that connects to a starter bolt to make the ground for the wiper motor and the A/C-Heater fan.
When you open the door the switch near the hinge compleates the circuit to ground and the interior lights go on. Your model may have a time delay which is an orange square behind the glove box.
You also need a good ground at the wiper switch.
If low and medium speed work on the A/C-Heater fan but not high speed, look under the left fender near the master cylinder for a bad inline fuse. PG.
When you open the door the switch near the hinge compleates the circuit to ground and the interior lights go on. Your model may have a time delay which is an orange square behind the glove box.
You also need a good ground at the wiper switch.
If low and medium speed work on the A/C-Heater fan but not high speed, look under the left fender near the master cylinder for a bad inline fuse. PG.
Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 828
Likes: 2
Jack
Go get an inexpensive low voltage continunity tester,turn every thing off then check from grnd to chasis or motor chances are you will be o.k. now check each one to a hot lead or install afuse and connect to batt.pos. should be hot. keep in mind that resistance can allso be a problem.
P.S. please tape off all bare wire's both pos, or neg the last thing you need is a burnt harness
JRL
Go get an inexpensive low voltage continunity tester,turn every thing off then check from grnd to chasis or motor chances are you will be o.k. now check each one to a hot lead or install afuse and connect to batt.pos. should be hot. keep in mind that resistance can allso be a problem.
P.S. please tape off all bare wire's both pos, or neg the last thing you need is a burnt harness
JRL
I am finding power in my ground wires and power with the stitches off in wires where they should be off.
I am also finding power wires that were not original that are exposed.
I have test lamps and continuity testers and variable power testers.
I just don't know where the switches and relays are in the car.
Jack
Burning Brakes
Joined: Feb 2009
Posts: 780
Likes: 1
From: Shelby NC
Jack, remember a corvette cannot get ground like a metal car for the obvious reason-it's not metal therefore it has a ground system almost like the positive side. Everything has to have a ground feeding it in someway. I always found that "Bubba" would find a way to cross the ground into the fire side somehow and then the problems start. It's there somewhere and you have to look until you find it. Most common seemed to be on the starter harness where the ground would be connected to the starter soleniod. It could also be where someone spliced in a wire and crossed the ground into a wire that was hot. It's always amazing how when you find it everything just goes back to being great. Like others have said--test lights and ohm and voltage meters will help in the process and you need. I'm restoring a 77 and it has been amazing what people will do when it comes to wiring. Coca cola and a pack of cheese crackers will do miracles for you--some problems require extra drink and crackers! You'll get it!
Burning Brakes
Joined: Oct 2004
Posts: 801
Likes: 17
From: Middletown Delaware
I just got done with the same problem on a 76. It turned out to be the wiper motor shorted to ground. This put about 10 volts into the ground at the lower wiper connentor and also over to the high speed blower relay. Blower was also inop. Never blew any fuses. Dave
Safety Car
Joined: Oct 2007
Posts: 4,367
Likes: 1,730
From: Seattle Area Washington
The link below is a complete color wiring diagram for both early and late production 77 models. The wiper/washer diagram is the last thumbnail picture on the page. Click thumbnail to enlarge. If your car came equipped from the factory with option ZX2 Convenience Group it came with the hood lamp along with other options.
Good Luck,
http://www.europeancorvette.com/html...l_diagrams.htm
Good Luck,
http://www.europeancorvette.com/html...l_diagrams.htm
Last edited by bmotojoe; May 28, 2009 at 09:49 AM.
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Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 828
Likes: 2
The link below is a complete color wiring diagram for both early and late production 77 models. The wiper/washer diagram is the last thumbnail picture on the page. Click thumbnail to enlarge. If your car came equipped from the factory with option ZX2 Convenience Group it came with the hood lamp along with other options.
Good Luck,
http://www.europeancorvette.com/html...l_diagrams.htm
Good Luck,
http://www.europeancorvette.com/html...l_diagrams.htm
Thanks!
Jack
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Didnt read everything but has anyone mentioned the black 14 g ground wire down at the starter ? If it has been installed (which is a very common problem on C3s) on the pos post of the starter it will cause this problem-12v on the black at the wiper. This 14 g wire needs to go to one of the starter mounting bolts or a bellhousing bolt,it is the ground for the wipers and the blower motor.
Safety Car
Joined: Oct 2007
Posts: 3,729
Likes: 267
From: Austin Texas
Corvette of the Year Winner 2017
2016 C3 of Year Finalist
if this GND. wire is not connected and you measure for voltage,
you will see 12v.
because it is floating and not tied to Gnd.
please don't guess what a wire is ??
thats how you get Bubba wiring.
follow it and verifiy what the wire is connected to.
then you will know for sure what to connect.
you will see 12v.
because it is floating and not tied to Gnd.
please don't guess what a wire is ??
thats how you get Bubba wiring.
follow it and verifiy what the wire is connected to.
then you will know for sure what to connect.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
And right next to that, if a wire that is SUPPOSED to be hot is connected to a ground and the battery is connected, the smoke will leak out of that wire, or worse, the component it's attached to.
Basic Law of electricity-
Everything works on compressed smoke- when the smoke leaks out, it will no longer function as intended.
Instructor
Joined: Mar 2008
Posts: 173
Likes: 1
From: New york New york
Jack
sorry about the delayed responce, there are a few relay's "connection box's" located in the console this is where I foung most of my problems in thirty years every Bubba and his bro. tapped in , disconnected added and only god knows what else. Check out Zip for an assembly manual this will be worth it's weight in gold, You seem to have the right equip. to trouble shoot now add alot of patience and keep asking the forum questions these guy's are a lot of help and very knowlegeable
Hope this helps JRL
sorry about the delayed responce, there are a few relay's "connection box's" located in the console this is where I foung most of my problems in thirty years every Bubba and his bro. tapped in , disconnected added and only god knows what else. Check out Zip for an assembly manual this will be worth it's weight in gold, You seem to have the right equip. to trouble shoot now add alot of patience and keep asking the forum questions these guy's are a lot of help and very knowlegeable
Hope this helps JRL
