Identifying electrical wires in LM

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mg9184
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Joined: Sat Aug 08, 2020 10:54 am

Re: Identifying electrical wires in LM

Post by mg9184 »

Thanks again for all the helpful information, I realized that the reason I couldn't find the brake light switch was because it was simply missing. I replaced the brake light switch, all of the rear bulb sockets, and any blown bulbs I could find with parts ordered from Clark's, and I made sure that the bulbs were the right type for each socket. Now almost everything works properly, except for the rear left hand turn signal/brake light and the rear left side running light, I think part of the wiring harness might have just corroded, because I've done everything else to make sure the bulb would light up.
joelsplace
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Location: Northlake, TX

Re: Identifying electrical wires in LM

Post by joelsplace »

That very well could be wiring but have you thoroughly checked the grounds?
157 Corvairs, 5 Ultravans and counting
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bbodie52
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Re: Identifying electrical wires in LM

Post by bbodie52 »

...except for the rear left hand turn signal/brake light and the rear left side running light...
The 20Y wire powers the left turn signal/brake light. A test with a multimeter should show if voltage is making it to the socket or the 12-pin multi-connector (firewall side/engine compartment side). The point of origin is the round Camaro-style multi-connector at the output of the turn signal switch at the steering column. The power sources are different (flasher and brake light switch). You already know that these voltages are making it into the turn signal switch, because the brak/turn signal bulb on the right side works. So the question is... are thos voltages coming out of the steering column switch for the left side?. The brake light switch is normal-through for both rear lights when the turn signal lever is in the middle (neutral() position. Unless there is an internal bad contact in that switch, you should find the brake light voltage coming out of the steering column on both the 20Y and 20DG wires (2nd and 3rd from the bottom in the diagram). It goes in via the bottom connector (brake pedal switch) abd back out frm the next to connectors to the right an left rear lights. The violt flasher feed is the 4th from the bottom, and is output only with the lever is moved to the left or right.

If you find the voltages output from the source (steering column), check bat to the engine compartment to see if it is making it to the 12-pin multi-connector. If that connector is the point of interruption, check for internal corrosion or bent/damaged metal contacts.
Most rear circuits route through the engine compartment multi-connector (below the voltage regulator, near the firewall). The number of metal connector pins inside depend on the Corvair model year, ranging from 8-12 pins. This rear multi-connector is a common source of trouble, as it is subjected to age, vibration, heat, and moisture for many years. Even when the outer plastic shell halves appear to be tightly connected, the internal metal pins may not be providing good electrical connectivity, as they may be loose, dirty, corroded, or bent.

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Permatex 22058 Dielectric Tune-Up Grease, 3 oz. Tube

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The left and right side marker lights get their power from the same source as the license plate light and the left/right tail lights. If all of these lights are functioning except the left side marker, check the bulb, socket, and socket ground.


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Brad Bodie
Lake Chatuge, North Carolina
Image 1966 Corvair Corsa Convertible
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will.west2
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Re: Identifying electrical wires in LM

Post by will.west2 »

Hello Brad,
I just joined the Forum this morning and had an informational post for you and the members.
I also have a 66' CORSA Turbo Convertible, but unfortunately without the turbo motor. It has
had the 140 in it for years and until this summer (it dropped a valve seat) ran like a top. I still
have a 65' Turbo engine in the garage that I can install when the weather warms.
My information is the following:
On a trip in the summer of 19' over the West Va mountains, with a full load and like an idiot, the
lower shroud pans installed, my CORSA overheat buzzer sounded. At first, I didn't know what that
sound was, as you describe in your posts, it never went off. When I realized what that sound was,
we pulled over immediately and were towed to our destination about 100 miles to the south.
My thinking is that even though it wasn't for that long a period of time, the event weakened the
valve seat enough to cause it to come loose. Moral of the story is don't travel during the hot
summer months with those shroud pans installed!
Hope this is of some help to the members of the Forum.
Thank you for all your tech tips and posts to this site. They have been most helpful.
Happy Holidays,
Bill Westr
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bbodie52
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Re: Identifying electrical wires in LM

Post by bbodie52 »

:wave: :welcome2: Welcome to the Corvair Forum!

:think: :idea: I appreciate your comments concerning your 140 hp engine overheating, but I wonder if you were too quick to point the blame for your engine overheat condition on those lower shrouds and the associated thermostat doors. If one of the thermostat doors was stuck in the closed position and not permitting the hot air to escape, that could be the cause. Other possibilities: If your fully-loaded, West Virginia hill-climbing Corvair was experiencing engine detonation due to tuning/timing issues, low octane fuel, possibly a vacuum leak causing a lean fuel/air mixture, or some other undetected cause — that could also be a cause of overheating. An engine compartment perimeter seal in poor condition can permit heated engine exhaust air to recycle back into the engine compartment, making it difficult to cool the engine adequately. A fan belt problem might cause inadequate cooling air flow. A torn, missing, or loose upper heater air hose connection can permit a cooling airflow problem that can result in a hot cylinder condition, with one or two cylinders deprived of adequate cooling air. Cooling fins that are obstructed by bedding "trash" deposited by invading "critters" that make there home under the top shroud can result in an overheated hard-working engine. (Which cylinder dropped its valve seat?)

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As you can see, there are several possibilities that can result in an overheated engine. Generally, GM did a good job of designing and testing the Corvair engine cooling system, and tested it in a wide range of driving conditions before it was unleashed on the public. Certainly the strenuous fan belt path caused some issues, most of which were resolved with the switch to a lightweight magnesium cooling fan in 1964, better fan belt materials and design, and belt guides. The lower shroud design and thermostat doors are, I believe, seldom the cause of an engine overheat condition.

When the overheat alarm sounded (triggered by a sensor installed on the right head), did you happen to note the temperature displayed on the Corsa temperature gauge? 400 degrees or less is normal, but this gauge only shows the heat from the left head sensor. A problem affecting the right side only may not be displayed on the temperature gauge.

It has never been necessary to remove the lower sheet metal shrouds during hot summer months to provide the Corvair engine with adequate cooling. The other conditions I mentioned have been known to cause overheat conditions, however. The large valve 140 hp heads are certainly more vulnerable to dropped valve seats — sometimes more common on cylinder 5, which can suffer from reduced cooling airflow related to the upper air hose location and its condition. I would suggest all of these possibilities be considered when looking for the cause of your engine overheat condition.

:welcome:

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Brad Bodie
Lake Chatuge, North Carolina
Image 1966 Corvair Corsa Convertible
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