serious electrical help needed...
Thread Starter
Melting Slicks
Joined: Feb 2006
Posts: 2,092
Likes: 5
From: Fayetteville Arkansas
serious electrical help needed...
so here's the deal... 1972 4spd 350 coupe , when I bought the car the thing ran and ran well even though it has only been started yearly for about the last three years. During the purchase the previous owner accidentally got the cables switched and for 20 - 40 seconds they were on the wrong posts. Neg was on pos and pos was on neg. It burnt up the 12R / 14 BRN wire cominng off the 3/8 post going up the enginne wire harness. I have since then replaced the starter soleniod and rewired all the of the poor splices correctly. When the battery is hooked up the positive is already on and then while trying to screw down the negative sparks are abundant and The 12R/ 14 BRN heats up again. I am not sure what is wrong but either something is not right or sommething was fried further up like the ignition switch when the polarity was switched. I have the AIM and chilton maual schematics and have ordered Don Olson's diagram along with a new engine wire harness and both positive and negative battery cables.... they will be here next week. Anyone have any clues????? or any other things to try to diagnose what might be wrong??? Thanks guys...
Thomas
Thomas
Last edited by Sully1882; Jun 22, 2007 at 11:27 AM.
Team Owner
Joined: Jul 2004
Posts: 40,375
Likes: 788
From: Redondo Beach, California
Melting Slicks
Joined: Jul 2005
Posts: 2,740
Likes: 3
From: Aurora Ontario
so here's the deal... 1972 4spd 350 coupe , when I bought the car the thing ran and ran well even though it has only been started yearly for about the last three years. During the purchase the previous owner accidentally got the cables switched and for 20 - 40 seconds they were on the wrong posts. Neg was on pos and pos was on neg. It burnt up the 12R / 14 BRN wire cominng off the 3/8 post going up the enginne wire harness. I have since then replaced the starter soleniod and rewired all the of the poor splices correctly. When the battery is hooked up the positive is already on and then while trying to screw down the negative sparks are abundant and The 12R/ 14 BRN heats up again. I am not sure what is wrong but either something is not right or sommething was fried further up like the ignition switch when the polarity was switched. I have the AIM and chilton maual schematics and have ordered Don Olson's diagram along with a new engine wire harness and both positive and negative battery cables.... they will be here next week. Anyone have any clues????? or any other things to try to diagnose what might be wrong??? Thanks guys...
Thomas
Thomas
Sounds like you melted it somewhere else. The 12r/14 brn is touching either a ground or another wire. To determine if its melted and touching metal do a continuity test. Disconnect the battery first. Set meter on continuity. Touch the 12r/14brn with one end of the meter and run the other end to metal. If you get continuity thats your problem. Now you need to find the exact location.
If there is no continuity between the wire and metal You have two live wires melted together somewhere. A little tricky to find. Same idea though. Battery disconnected. check continuity from the 12r/14brn to every other wire in that harness.
Jim
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Racer
Joined: Mar 2006
Posts: 343
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From: Davenport Ia
The easy way to find out would be to unplug the alternator and unhook the output wire (this should only be done with the battery disconnected, the output wire is the heavy wire on the screw terminal at the rear of the alternator). Be sure to tape the output wire off temporally. Then try to reconnect your battery. If the sparking get less or quits your alternator has issues. Hooking the battery up backwards usually ruins the rectifier and regulator. On your car the regulator is built in to the alternator.
Last edited by HO-alts-Rick; Jun 22, 2007 at 11:27 PM.
Melting Slicks
Joined: Mar 2005
Posts: 2,094
Likes: 298
From: Midlothian VA
Check that you simply didn't hook the engine harness ground wire (black with the large lug) to the large hot lug on the starter soleniod by mistake. This is a frequent mistake by new owners. The engine harness ground wire has a large lug on it because it is supposed to be attached to the starter retaining/mounting bolt. Unfortunatley it looks like it's supposed to attach to the hot side of the solenoid due to its size. Result...dead short when you attach the battery.
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
Check that you simply didn't hook the engine harness ground wire (black with the large lug) to the large hot lug on the starter soleniod by mistake. This is a frequent mistake by new owners. The engine harness ground wire has a large lug on it because it is supposed to be attached to the starter retaining/mounting bolt. Unfortunatley it looks like it's supposed to attach to the hot side of the solenoid due to its size. Result...dead short when you attach the battery.
Thread Starter
Melting Slicks
Joined: Feb 2006
Posts: 2,092
Likes: 5
From: Fayetteville Arkansas
got her up and running...
so I went through the wiring diagrams and got it all straight and cleaned up and once in place everything was perfect and the car started right up! Thanks all for the pointers and words of wisdom! The problems were with the 12R wire being overloaded from the blower moter 14B placed on the starter... it is all fixed now. The car has a few other things to get in order before driving like a complete service and fluid change. I started that last night and will finish it soon enough. Then time to blled the brakes and flush the whole system. I also plan on upgrading the distributer to an HEI style soon and getting away from the old points style that is still in it. Overall the car is complete and in great shape... the frame is wonderful and there's not really rust anywhere...I am still just amazed at what I got for the money... I mean I just got a steal...
Melting Slicks
Joined: Dec 2005
Posts: 2,441
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Thread Starter
Melting Slicks
Joined: Feb 2006
Posts: 2,092
Likes: 5
From: Fayetteville Arkansas
http://forums.corvetteforum.com/show....php?t=1717996
yeah bought it from private party of whomo had neglected the car for the past number of years... he had lost interest and care and I benefited from it!
Sully
yeah bought it from private party of whomo had neglected the car for the past number of years... he had lost interest and care and I benefited from it!
Sully