lgrant

Does anyone know what the voltage is coming out of the TCU to the solenoids. I'm guessing that it is the same for all three and that it is something less than 12V. A couple of years ago, my TC clutch wouldn't stay locked up when it should have and the solenoid tested high on the ohms (in the 40+ range) so I wired around the TCU with battery voltage (switched of course) and when you flipped the switch, it would lock up immediately and stay lockup. Lately it will not lock up and I tested the solenoid again today and got an ohm reading of 197, indicating the resistance has gone up quite a bit. I want to change out the solenoids but I want the understand what's going on first. If the TCU voltage is noticably less than battery voltage (perhaps 5V) then it all makes sense. If they are the same then I'm suspecting the TCU in addition to a bad solenoid.

Vehicle is a 96 Cherokee. BTW, cruise control works fine (brake switch) and changed out TPS and VSS.

Thanks to all in advance.

Radi

Did you measure the voltage with the solenoids connected? Bad one might be pulling the bus voltage down to something less than 12V. And 40 ohms is too high, 197 is really too high. 11-15 is normal.

lgrant

No I did not measure the voltage - I thought I might find out what it's supposed to be from someone on this forum. I suppose I can figure out a way to measure if necessary - maybe I'll have to lift the rear tires off the ground and accelerate the drive train to 42.5 mph which would cause the TCU to try to fire #3. Assuming that the "no load" situation didn't change the simulation too much, then it could be measured with a multimeter. The problem with that is it will only tell me what my TCU is putting out - not what it should be.

Here are the issues: solenoid 3 looked like it was failing 2 years ago. Today it looks like it's toast. That said, 2 years ago battery voltage would activate/fire it while the signal from the TCU was not sufficient to keep it activated/fired. I was hoping that someone could confirm that the voltage from the TCU required to fire a healthy solenoid was designed to be less than 12V and is, indeed, normally less than 12V.

Radi

Best I can tell without actually going out there and measuring it, the solenoids appear to operate on battery voltage, not a reduced voltage. You could backprobe the TCU connector and see what yours is supplying while you drive.
Might also make sure the TCU is getting good voltage coming in. If it's low coming in, it will be low feeding the solenoids too.

lgrant

Yes I think "low voltage coming to TCU" is worthy of further analysis. If the TCU is supposed to put out 12V, it's clear that mine doesn't since wiring around it temporarily solved a problem.

I'm headed out for deer hunting - will get back to the project when I get back.