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Topic: Mystery switch

in Forum: C3 Electrical


Mystery switch

Posted: 1/9/05 1:14pm Message 1 of 10
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DeBerry, TX - USA
Joined: 2/27/2002
Posts: 1006
Vette(s): 1971 383 Stroker- mille miglia red...5 speed
Does anyone know what the switch or relay is screwed onto the a/c housing under the hood? It has three wires going to it, one yellow, one brown and one black. Mine fell apart. It has a copper coil and what looks like a maybe a breaker on one end inside. It's about 2"x 1 1/4" x 1 1/4".
Also on a different note, any ideas on why my engine falls on it's face at around 4600-4700rpms? It feels like it just runs out of gas till I back off.(71' 350/270 stock, Holly 600 vac. Appreciate the help. Dwain |headscratch|


   I know the voices aren't real, but they have some pretty cool ideas...

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Mystery switch

Posted: 1/9/05 1:30pm Message 2 of 10
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KERNERSVILLE, NC - USA
Joined: 1/13/2004
Posts: 1355
Vette(s): 1968 L-71 convertible
Replace the fuel filter.


Mystery switch

Posted: 1/9/05 1:31pm Message 3 of 10
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DeBerry, TX - USA
Joined: 2/27/2002
Posts: 1006
Vette(s): 1971 383 Stroker- mille miglia red...5 speed
Did that today...no difference


   I know the voices aren't real, but they have some pretty cool ideas...

Mystery switch

Posted: 1/9/05 2:59pm Message 4 of 10
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Frederick, MD - USA
Joined: 9/8/2003
Posts: 3398
Vette(s): 1969 convertible L71 427/435 4-speed black interior
The relay you describe is the heater blower motor resistor. It regulates the hi-low motor speed. Most any of the parts houses or a GM dealer should have it or get it for you.


Mystery switch

Posted: 1/9/05 6:32pm Message 5 of 10
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CUYAHOGA FALLS, OH - USA
Joined: 12/2/2003
Posts: 6424
Vette(s): 1975 C3 Red, T-Tops, Black Interior. All I need is time and money! Getting there!
If you have a stock HEI you may find the ignition module is breaking down under high RPM. They do that sometimes. Not uncommon. Connect a dwell meter to the negative side of the coil and see if it stays consistant at hight RPM. You drive and have some else watch the meter. The dwell will change at high RPM, but it should be consistant, and not bounce around.

A weak ignition coil will do the same thing, as will worn plugs and plugs with too large of a gap.

|UPDATED|1/9/2005 6:32:43 PM (AZT)|/UPDATED|



Mystery switch

Posted: 1/10/05 7:45pm Message 6 of 10
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DeBerry, TX - USA
Joined: 2/27/2002
Posts: 1006
Vette(s): 1971 383 Stroker- mille miglia red...5 speed
Thanks Ken. I do have the Petronix Ignitor II and Flame-Thrower II coil, fairly new. Could it be a fuel delivery problem? Like when I'm getting on the freeway, hit high rpms in second or third and shift, sometimes it just stalls for a couple of seconds then catches up and goes on. Maybe carb problem? If so, what could it be? Float level too low? Fuel pressure too low??? What are your ideas? Thanks, Dwain


   I know the voices aren't real, but they have some pretty cool ideas...

Mystery switch

Posted: 1/10/05 8:45pm Message 7 of 10
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CUYAHOGA FALLS, OH - USA
Joined: 12/2/2003
Posts: 6424
Vette(s): 1975 C3 Red, T-Tops, Black Interior. All I need is time and money! Getting there!
Even with the new ignition parts, I would do the ignition test.

But yes, it could be fuel related. The best test is to put a pressure gauge on the fuel inlet to the carb and watch the pressure when you are driving. Granted, this takes a fairly long hose. I have taped the gauge to the windsheild many times.

If the pressure goes away after prolonged hard acelleration, then comes back, you have a fuel deliverly problem.

This could be a partly clogged pickup in the tank, a weak pump, collasped flexable fuel line, etc.

If the pressure is good, you can try replacing the filter.

Usually the float won't be a problem if the car ran good in the past, and the carb has not been opened up. When a float fails, or the needle and seat fail, it usually runs too rich or floods. Not your problem.
While the needle and seat can stick shut and cause starving problems, it does not usually act up in the manner you describe.

My car is doing a very similar thing at the moment, but it takes a bit longer to recover. My "s" shaped hose from the frame to the fuel pump has been replaced with standard hose sometime in the past, and the hose collaspes and restrictes the fuel under hard acelleration. I have the new hose, but need to put it on.

You could also hook a propane tank to the the air inlet, and when the car boggs (not until), add a lot of propane. If it runs a bit better, or runs well, it's starving for fuel. If it makes no difference you either don't have enough propane, or it's an ignition problem. The flow from a propane torch is not enough. There are valves that go on the propane tank that can deliver a lot more volume through a vacuum hose.

Starting fluid (either) can be used and sprayed through a hose, but I don't recommend it. The starting fluid burns too fast and can cause severe pinging, and under heavy load could cause engine damage.

Try a few things and let me know what you find. Well go from there.


Mystery switch

Posted: 1/10/05 9:10pm Message 8 of 10
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DeBerry, TX - USA
Joined: 2/27/2002
Posts: 1006
Vette(s): 1971 383 Stroker- mille miglia red...5 speed
Thanks for the info. I'll see what I can find...........


   I know the voices aren't real, but they have some pretty cool ideas...

Mystery switch

Posted: 1/11/05 6:45am Message 9 of 10
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Kingston, TN - USA
Joined: 7/5/2003
Posts: 900
Vette(s): 1970 Vert Both Tops Kiesler 5 Speed Steeroids Rack and Pinion Stayfast Convertible Top
One more thing, when you set up the Pertronix, did you set the end play on your distributor? I have the original Pertronix and that was one of the things that was to be done while installing the module. I don't know if it is still critical with the Pertronix II though.


Mystery switch

Posted: 1/11/05 7:14am Message 10 of 10
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DeBerry, TX - USA
Joined: 2/27/2002
Posts: 1006
Vette(s): 1971 383 Stroker- mille miglia red...5 speed
Hmmmm...I don't know, I didn't install it and don't have the directions. How would I check that? Thanks


   I know the voices aren't real, but they have some pretty cool ideas...

in Forum: C3 Electrical


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