Hello every vette owners.
My vette is a C3 from 1975 with a TH400. Unfortunaly, my kickdown don't work since i run with the car. I tested the solenoid and i heared it work. But i have no 12v on the orange cable. Papawana send me the wiring diagram, but nothing can help me to correct my trouble. How it is possible to test it. Does the motor run while i try the throttle switch ? My tachometer don't work too. Is there any connection beetween the kickdown and the tachometer? If someone could help me, it would be very nice.
PS: sorry for my english and the mistake i made.

 

You can test the throttle switch without the engine running. Turn the key on, and press down on the accelerator pedal (or push the slider on the switch), and when the switch lever is at full extension, see if you have 12V coming from the switch with a test light or voltmeter.

I'm not sure about '75, but ealrier tachometers were mechanical (cable) from the distributor.

Should not be related to kickdown function.

I think you described your situation clearly.

Steve

 

The tach is an HEI version for 1975 - there is a circuit board behind the tach and that could be the problem. In regards kickdown - there is a switch that is activated when you push the gas pedal down - this one switch controls the hood solenoid and the kickdown solenoid at the tranny - you might want to replace that switch. Since you have a '75 also here's another check to perform - remember that the engine and tranny must work together - there is a modulator at the tranny that can sometimes get plugged up causing performance problems. Check it out if needed or get a new one.

 

According to one source a new tach circuit board repairs 95% of tach problems - cost about $60 - check wires on distributor for other 5% of problems. The kickdown switch is GM part # 1242101 per page 425 of the AIM. You will still get the engine "roar" with wide open throttle even if the hood solenoid isn't totally open. Do fill out your profile.

 

Hey Mac nothing wrong with your English I think its cool .Any way where the hood and the winshield come together open the hood follow the wire up the hood to the electrc door opener that opens when you kick it down and take the door off so you get more fresh air all the time My car is still stored (1975) so if you dont find the kick down problem do another mail next week and ill check it out on my car.my kickdown works but my 400 seems to be slipping so re-build to the resque. welcome to the forum and you will be able to fix that problem I would think without much problem.

 

Put the key in the accesory position with the car not running,

Reach down around the top of the gas pedal armature and you should be able to locate the kickdown switch. Grab a small flashlight and lie with your head under the deah to get a good look at it, if you are not sure xactly where it is. You should be push the plastic arm of the switch manually towards the front of the car and here a click in the transmission. If the cowl induction is also hooked up and working, the cowl flap should also open at the same time. If the above works by manually moving the switch, then I imagine the actual gas pedal rod is not making good contact with the switch and not kicking down when you hit the gas.

The cure that I found that worked to get the gas pedal to engage the switch completely was to remove the before mentioned switch (one electrical connetion at the switch and two scews) and place a piece of rubber gas line over the plastic "tube" part of the switch. Others have wrapped this section with several layers of tape to make this part of the switch larger in diameter so that it fully engages when the gas pedal is pressed. I found a piece of gas line to work perfectly. If still not enough engagement, get another piece of rubber hose that will then fit snuggly over the gas line to again increase the diameter of the switch lever so that it make good contact when the gas pedal is pushed down about half way. The above fix worked great for my previous 74 and on my father's 75.

 

Thank you very much for your lots of answers