Yellow Wire in Engine Compartment Melted?

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19corvair62
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Yellow Wire in Engine Compartment Melted?

Post by 19corvair62 »

Hello guys,

I was taking apart the engine compartment a few weeks back to prep for bodyshop work and painting. As i'm fiddling around with the engine wiring harness, disconnecting the tail lights and such, I notice that the yellow wire that comes from the multi-pin connector at the firewall to the positive of the Ignition coil had the insulation melted away and wire exposed at a couple of places.

Does anyone suspect how this happened? Seems like the wire overheated and cause the insulation to fail. :think: She ran beautifully despite the wire in such condition.

I'm trying to reorder a new wire from Clark's but I cant find it in the catalog, pages 97-100. Can anyone tell me if they sell this wire alone or must I get the complete Engine Harness, part # C8350?

I had some great pictures depicting the damage, but I accidentally deleted them on my phone and the car is not at my reach at the moment.
Matthew

1962 Corvair Monza 102 HP 4 Spd.
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Re: Yellow Wire in Engine Compartment Melted?

Post by bbodie52 »

I have combined the schematic wiring diagrams for the 1962 Corvair INTERIOR and ENGINE COMPARTMENT into a single wiring diagram so that it is easier to trace each circuit from the engine compartment to its associated connection points in the instrument panel, dashboard area, etc. I also included the engine compartment schematic alone.

It appears that the yellow wire you are referring to is one of two wires connected to the positive terminal of the ignition coil. The yellow wire is only active when the engine is being cranked by the starter motor. When the solenoid engages the starter, it simultaneously applies a full 12V DC to the yellow wire, to provide the ignitio coil a full 12 volts to temporarily boost the primary coil voltage. Increasing the primary voltage has the effect of boosting the spark plug voltage. The is done to enhance engine starting when cranking the engine.

When the engine starts, the driver releases the key and the ignition switch returns to the ON position. The starter solenoid disengages the starter, shuts off power to the starter motor, and discontinues providing voltage to the yellow wire that is connected to the ignition coil. This leaves only a nominal 7V DC to power the coil, which is provided by the other wire (marked 20 W/R/B) which is a special resistor wire in the wiring harness. The purpose of lowering the running voltage that is provided to the coil is to reduce the voltage and the current that passes across the ignition points in the distributor. These points are an electrical switch, which are continually opening and closing the coil circuit from the negative terminal to GROUND. When the points close the primary circuit in the coil is energized, to build an electrical field. When the points open this electrical field collapses, which induces a high voltage across the secondary winding of the coil, which is directed by the distributor to the appropriate spark plug. The lower spark voltage provided by only 7V DC in the primary winding is adequate for normal engine operation, and reducing this voltage from 12V DC to 7V DC helps to reduce burning and arcing of the points contacts, which prolongs the life of the ignition points.

If you follow the 20 W/R/B wire back from the coil, you will see it becomes a special resistor wire to reduce the source voltage. On the other side of the 8-pin multi-connector, the wire is labelde 18 BRN and it continues to the harness that is routed to the instrument panel. When it passes through another multi-connector, the wire is labeled 18 DG and rutes to a power junction point in the wiring harness. All wires tied to this junction point are powered by the 14 DG wire coming from the ignition switch. These switched circuits include the ignition coil, engine warning lights, the fuel gauge, and other circuits protected bvy the fuse block.

So the yellow wire you are concerned about is only a short pigtail wire coming from the starter solenoid, through a 2-connector multi-connector near the firewall. The thicker wire in this two-pin connector (12 V) comes from the ignition switch, and provides voltage to the starter solenoid when the driver turns the switch to START (causing the starter to engage and crank the engine). The thinner yellow wire applies battery voltage to the ignition coil — as previously described — to temporarily provide a "hotter" spark voltage to the spark plugs.

Left click each image to enlarge the picture for improved viewing...
1962 Combined Passenger Compartment & Engine Compartment Wiring Diagram.jpg
1962 Corvair Engine Compartment Wiring Diagram.jpg
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The cause of the melted insulation that damaged part of your wiring harness is unclear. The wire itself may have some damaged strands that could reduce its current-carrying capacity, causing it to overheat. Or an electrical short to ground may have occurred at one time that caused excessive current to pass through the wire — melting the insulation.

If the portion of the damaged harness is on the side that connects to the solenoid, you can purchase that short pigtail if desired. It is listed below. If the damaged portion is between the coil and the connector, you can purchase some 20 gauge yellow wire and replace the damaged segment between the coil and the connector. Individual connectors and metal connector components are listed on page 100 below.

:link: http://www.corvair.com/user-cgi/catalog ... ow_page=97
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Part number C2266: DUAL FEMALE RECEPTICAL STARTER WIRE

Weight: 0 lbs 6 oz
Catalog Pages(s): 97
Price: $15.05


:link: http://www.corvair.com/user-cgi/catalog ... w_page=100
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Wiring Circuit Color Code.jpg
The 1962-1963 wiring supplement is also attached below...
Attachments
1962-1963 Supplement - Chevrolet Corvair Shop Manual - Section 8 - Electrical Systems.pdf
1962-1963 Supplement - Chevrolet Corvair Shop Manual - Section 8 - Electrical Systems
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Brad Bodie
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Re: Yellow Wire in Engine Compartment Melted?

Post by 19corvair62 »

Bbodie,

I understand the concepts that you are explaining, however, there is only one wire connected to the positive terminal of the coil.
6281984 (1).JPEG
As you will see in the picture, the rear side of the coil is the negative side which in which the wire that comes from the distributor connects to; the front (+) has the yellow wire (which is the disconnected one in photo) and the wire from the noise suppressor.

It appears that maybe the electrical was tampered with at some point before my acquisition. How would the vehicle be operating then? Would the coil be receiving a constant 12V from the electrical system?

I think in this case I might be better off replacing the Engine harness to correct this . What do you suggest?
Matthew

1962 Corvair Monza 102 HP 4 Spd.
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Re: Yellow Wire in Engine Compartment Melted?

Post by vairygood »

Impressive work Brad.
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Re: Yellow Wire in Engine Compartment Melted?

Post by bbodie52 »

I assumed your 1962 Corvair was wired in accordance wqith the 1962 schematic provided in the supplement. However, at some point in the production cycle Chevrolet modified the wiring harness, as shown on page 8-23 (Fig. 8-34), which shows the 1963 configuration.

In the 1963 schematic, only a single yellow wire is connected to the positive terminal of the ignition coil. This wire is routed to the 2-pin connector coming from the starter solenoid. At that point the wire is spliced so that it is connected to BOTH the yellow wire coming from the solenoid, and the wire labeled 20 W/OR/PPL (resistor wire) coming from the 8-pin multi-connector. On the other side of the 8-pin multi-connector it still switches to 18 BRN as it routes forward to the instrument panel wiring harness to pick up voltage from the ignition switch when it is in the ON position. This is likely the configuration you will find if you trace the yellow wire back from the coil positive terminal to the 2-pin connector that comes from the starter solenoid.

Electrically this is still the same as the 1962 configuration. The only difference is that in 1962 the two wires were "spliced" by physically connecting them both at the coil positive terminal. In the 1963 configuration, the two wires are spliced at the starter harness, leaving only a single yellow wire to be routed to the coil. (This new configuration that was introduced in the 1963 schematic diagram was continued and retained in 1964-1969).
1963 Engine Compartment Wiring Diagram
1963 Engine Compartment Wiring Diagram
If you are willing, you might consider converting your ignition system to a breakerless system that eliminates the ignition points and condenser completely. The Crane Cams system offered in the Clark's Corvair Parts catalog uses an electronic module that is optically triggered by an LED system. It is maintenance-free, well-respected, and reliable. The Crane Cams electronic module runs on the 7V DC power provided through the resistor wire.
RECOMMENDATION — If your feeling extravagant and want increased reliability, you might consider eliminating the points and condenser, and the wire, completely and upgrading your distributor with an electronic, breakerless ignition system. These systems replace the antiquated points with a system that controls the coil with either a light beam or a magnetic pulse. The Crane Cams system seems to be slightly preferred over the Pertronix unit. I installed the optical trigger version years ago in one of my Corvairs and I would never consider going back to ignition points.

:link: http://www.corvair.com/user-cgi/catalog ... IN&page=74
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Brad Bodie
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Re: Yellow Wire in Engine Compartment Melted?

Post by 19corvair62 »

Bbodie,

I believe my '62 is a late produced Corvair, maybe that is why it has the wiring harness used in '63+ models? I will soon post a VIN decode to verify.

When I get the car back from the bodyshop, I will check this area where the wire splices and inspect the wire and replace if needed. The car runs fantastic IMO with the old point-set system, if I ever run to problems down the road, an electronic ignition system would be a thought to consider.

I will probably purchase the starter wiring harness to replace from the 2 pin connector to the starter, and then purchase 18 gauge yellow wire with the respective connectors to change from the 2 pin connector forward.

Thanks for your quick and detailed responses Bbodie! :ty:
Matthew

1962 Corvair Monza 102 HP 4 Spd.
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Re: Yellow Wire in Engine Compartment Melted?

Post by 1949chevy »

A wire coming from the starter to the distributor has one purpose...it is to give 12 volts vs about 8 volts (normal running volts on the coil neg side) to the plugs when you turn the switch to start...this wire should be connected to the pos side of the coil...it only works when the starter is engaged. Also , the resistor wire ( either a wire that produces resistance to cut the voltage or a wire coming from a white ceramic resistor that cuts the voltage to about 7-8 volts so the points do not burn up are connected to the pos side of the coil....

According to Clarks...62/63 spyders had the ceramic coil....

For example, my 68 corvette has the resistor wire vs the ceramic resistor ballast coming to the pos side of the coil...If it only has the resistor wire and not a white ceramic ballast resistor....that wire will be very stiff...it is not stranded like normal car wire which is stranded so it does not break...but gives some.

I have wired 3 street rods from scratch...no kits...all had pw, one a power cowl vent on my 55 ford pu truck, p seat, all had air, ...every wire in it...even 3rd brake light which they never had.
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Re: Yellow Wire in Engine Compartment Melted?

Post by terribleted »

The wire in your photo is not completely stock and the terminal is not stock at least. If it is fried do not use it. You must find out what voltage it provides when the ignition is in the run position. If it is 6-8 volts that is fine for a points ignition and stock. If it is 12 volts that is too much for points but would work fine with a proper aftermarket points replacement ignition that requires 12 volts. The wiring and voltages delivered must be correct for things to operate properly. The engine bay wiring harness is not terribly expensive and will provide fresh un-corroded connectors (the big on that plugs to the main body connectors is very prone to corrosion and burning), All new in burned wires, and all new tail and backup lamp sockets. I would suggest replacement.
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