Might have found the problem -1991 535i not starting in cooler weather
I have finally had some time to troubleshoot my car problem.
It had still been giving me problems not starting in the morning but it would start in the afternoon.
It wouldn't start for me one day and so it sat for a few days - then the batttery went dead. So I got it re-charged and it fired right up. I started searching forums and found out how to test for something that might be drawing current.
I went out and bought a new digital multi-meter (one that is fused). I set it to 200 mA, disconnected the negative battery terminal and ran the leads on the multi-meter from the negative post to the negative clamp - it blew the fuse in my multi-meter.
So I took the car down to Autozone and had them test the alternator - they said the diodes were OK but it was only putting out 30A. They tested the battery and it is fine - it is about 2 years old and is rated at 600 Cold Crank Amps but it was only at 67% charge.
So I have a new alternator on order.
The weak battery probably was why it wont start when it is cooler out.
Now with the alternator disconnected, I need to get a new fuse (or three) for my multi-meter and check to see if anything is still drawing down the battery. I'm hoping it was the alternator (even though they said the diodes are OK). If it is still drawing down, I have found instructions on how to isolate it.
Anyway - I thought I should post an update to let everyone know that helped here that I might be on to something. Once I get the new alternator in I'll see how things run for a while and then I'll post another update.
Thaks again to you and all the others that replied.