Diagnostics is the sum total of experience and conception.
Experience leads us to the reply: it's a blue car so it must be the Battery. Experience also leads us to which end of the wire to start on.
Conception is what one uses in ones mind to assemble all the pieces and dream of a condition that could cause an occurance.
You stated a condition: that your radio kept playing if your doors were left open with the key turned off. Experience tells me that there IS a system that changes on/off capabilities naturally with the door opening. That system is the power seats. They work with the key off; when the door is opened but not if closed (then the key must be turned on.
In my case, experience also tells me that the diode that allows this to happen does fail in ways that turns certain circuits on that shouldn't be. SOOOOOOOOOOOOOOOOOOOOO, in your case I conceived that this could happen and I went to my wiring diagram and verified that a shorted diode would power fuse #1 which is the one that turns the radio off with the key. My diagnostic job is done. I have hypothesized an exact condition that can cause such an event. The next step is to validate the hypothesis.
If I were working on the car, I would have done the hard work at this point (by confirming with research that the circuitry is right for my hypothesis). The easy job of verification has to be left to you (you have the car - if I would have had it I would have proved or disproved my hypothesis in less time than it took to write the first post). The testing required to validate the hypothesis has been explained (twice). The time for talking is over (except to exchange new hypothesis).
The point is: to hypothesize and test. This is the way to an answer. If one is really good one hits the right hypothesis first time every time (actually substitute God for good). There are a limit to the realistic possibilities but working without a basis can creat new ones.
Bosch Master, ASE Master, L1
33 years MB technician
Last edited by stevebfl; 05-25-2002 at 09:38 AM.