Just found this site. It's fantastic. Thought I'd stump you all with an elctrical gremlin problem:-)
My 91 300TE 4M w/66K mi., showed classic signs of battery end of life. Long trips okay short trips, dead battery over night. Not just low, DEAD. Clock stopped, radio CODE when turned on, no dash warning lights at start position, nada. Put in a new Optima battery, same thing occurs. Changed the fuel filter the same day as I put in the Optima cranked it a bit getting the fuel up to the CIS, etc., moved the car around the driveway and parked it. Next morning, dead.
Testing procedure as follows: Turn all light switches to off, ACC to off, radio off, shut doors. With fully charged battery in the clean and well tightened cables, open fuse box and test each fuse from its top end to ground with multi-meter. Four circuits are using voltage. C, D, 9, 10. Switch multi-meter to DC amps highest scale is 200mA. Pull fuses from four circuits. Place one test lead in bottom of fuse holder on on top tang. 10 and D show 0.00 current. How can this be? Circuits 9 and C go off the scale - being digital it displays a 1 at far left of LCD. How can this be?
I thought I'd try this next procedure but don't know what I discovered:
With multi-meter in DC amp mode 200mA scale, I put the red test lead to the top of the fuseless fuse holder in #9 and the black test lead to ground. I got a reading of 124.45 mA and it started to descend very slowly, as if I were draining a battery. Did the same to "C" and got a reading of 0.42mA and it started the descending thing. I switched the meter to DCV and used the same procedure and got readings of 7.34DCV and 4.32VDC respectively. Now I'm totally confused.
I must be doing something wrong. How much current should the clock and the various memory circuits be using? What is the proper placement of the test leads?
I feel a bit like Alice must have after jumping down the rabbit hole!
Any help would be appreciated.
Happiness is a well stocked