th400 kickdown quit

[baxsom]

ok so for the second time my th400 quit going into passing gear.
i crawled under the dash with the key on and pushed the switch by hand. no click from the tranny.

i thought ok the switch is bad like last time.

i unplugged the switch and jumped the terminals from the wire.
still no click from the tranny

i got out my voltmeter.
one wire has 12v with the key on like it is supposed to.

i reconnected the plug to the switch. i put both ends of the voltmeter on each terminal and turned on the key and get a constant 12v with the switch in the up position. if i press the switch to the engaged position the volts go to 0.

any ideas on what could be wrong. it seems i get 12v going through the switch with it in the up position but no voltage with it in the down position like the pedal is to the floor.

if i take the switch out and wire it into a simple battery to light circuit
the light is off with the solenoid switch in the up position but the light goes on in the WOT position so i know that the switch itself works.

 

[73shark]

The fact that the switch has 12V across it in the open position and 0V in the closed position indicates that the switch is working. Now need to check the terminal at the tranny to sse if you are getting 12V there.

 

[baxsom]

i am getting 12v at the orange wire on the tranny if i ground the voltmeter to the engine block.

if i stick the neg probe into the black wire on the plug i get no current.

 

[73shark]

Then whatever the 12V is supposed to actuate apparently isn't working.

 

[Rodney Gold]

If you hear no click , the kickdown solenoid is probably faulty , replace it.

 

[baxsom]

so far i am leaning more and more towards a bad ground.
the kickdown worked fine the last time i drove it.
and considering that right now the ground wire is not grounded says a lot.
my next test is to rewire the plug with a known good ground and see what happens.
after that i guess i have to drop the pan.

good thing i had that B&M drain hole installed.

 

[LLC5]

so far i am leaning more and more towards a bad ground.
the kickdown worked fine the last time i drove it.
and considering that right now the ground wire is not grounded says a lot.
my next test is to rewire the plug with a known good ground and see what happens.
after that i guess i have to drop the pan.

good thing i had that B&M drain hole installed.

It sounds like you are on the right track and doing everything correctly. You need to find out where the black wires goes to and find out why it is not grounded, a wiring diagram will be needed, I don't have one or I would look it up for you. It's possible that the black wire goes to another switch and not just to ground, it would be a good idea to know for sure before running the black wire directly to a ground source. Hopefully someone here has a wiring diagram and can let you know for sure.

 

[baxsom]

ok so here is what i have now.
i hooked a dedicated ground and power to the solenoid and i get nothing so it looks like i 100% now need to drop the pan and replace the solenoid.

damn

 

[73shark]

On the bright side, you have a drain plug so you don't have to deal w/ the splash of tranny fluid.

 

[baxsom]

On the bright side, you have a drain plug so you don't have to deal w/ the splash of tranny fluid.

peachy hahaha