|
Thanks.. I found the thread and it's given me encouragement to give it a try.
What I already knew:
TC is unlocked until 70mph in 5th or 65mph in 4th, if you change from 4th to 5th at 65mph the TC remains locked through the change. I've used this to engage lock sub 70mph in 5th.. I then use the cruise control to prevent it unlocking... very tricky on the driving though as you are driving on a bit of a knife edge speed wise.
I've now established the following.
Solenoid DC impedance is 3.0 ohms
When 'locked' the solenoid is pulse at 100Hz, the voltage across it reads as ~0.8V which in a 14V system means 100Hz pulses with a 1:20 mark to space ratio.
The TC is not even partially locked below 65mph.
I already know the TC never fully locks, being MB I don't know if this is because the TC is effectively 2 TCs, use one at low speeds and both at high speeds, or if it is scrubbing the TCC when 'engaged'.. I do know the TCCs wear out, mine did about 50,000 miles ago.
What I do know is that if you put 14V across a 3ohm load you will dissipate 50W, so I'm 99.9% certain I'd blow the solenoid if I just pull the control wire with DC.
Oh.. and with these mercs, the Solenoids are held at 12/14V and then grounded to activate.
Making a 100Hz PWM controller driving a FET to pull the TCC control line will not be hard for me... I'll probably use a PIC micro to do it.
Derek
|