Would You Suspect This to be the SI Batteries...?

[BBDirtbiking]

Alright, I am going to start from day 1 here. (1991 BMW 318is) *If I refer to tach not working, the fuel usage gauge also does not work, seem to not work together.

So, I am looking at this car, and just talking to the previous owner before actually seeing the car, he told me the Tachometer didn't work and suspected it to be the SI Batteries, well researching it, it seems to be a very common issue on the E30. Well I go and look at the car, when I first get there, the tach is working, said it worked all the way over to where we were meeting. So I give the car a good looking over, everything checks out, so its test drive time. I notice on my test drive that the tachometer doesn't work again... Weird. On my way home, I was just having fun in the car on the curvy mountain pass, and out of no where, after revving the engine with the clutch in, I notice my tachometer started working! Well, it turned off and on a couple more times on my 2 hour drive + 30 minute traffic jam on the way home.

Well, the next day I was showing some friends the car, and the tach didn't work in the morning. Well, I had the battery out and I cleaned up terminals and added some water to the cells and had my charger on it a little bit. The tachometer worked after that until I took the gauge cluster out.

So I had the gauge cluster out and had the SI batteries exposed. Before getting right into it and replacing the batteries I had the voltmeter out, the batteries both measured 2.96V, which is pretty close since they are 3V batteries, but usually they measure over the noted Voltage. (I have the Lithium batteries)

Well, after replacing some burnt out lights (brake wear sensor, turns out I need new brake pads according to it, haha, shouldn't have replaced that burnt out light :p) I put the gauge cluster back in, turned on my car and... NO TACH or fuel usage gauge! :mad:

I am now confused, could it still be those batteries!? Or would it be something else like a horrible connection with something. What makes me really confused is that the fuel usage gauge and tachometer do not work together, or work together... Which might rule out a bad wire? I could see how it is the batteries... might have to replace those?

Please get back to me with any suggestions or ideas on what I can do to fix this!

Thanks,
BBDirtbiking

[BBDirtbiking]

Does anyone know anything about Lithium Batteries, I read somewhere that if they read below the 'stamped' Voltage that they are junk... But I know on regular batteries that isn't the case. It seems like that since they are rechargeable batteries they should always be well over 3V, like a car battery is 'stamped' 12V but will read about 13V and then higher when the car is running, assuming your alternator isn't junk.

I might ask my professor tomorrow and pick his brain on the matter... he is pretty knowledgeable on batteries.

[BBDirtbiking]

Found the problem I think.



You can see how the wire is all messed up, it must have gotten really hot judging by the colour around it... Going to sadder a new wire on there and hopefully the Tachometer and Fuel Usage Meter work all the time instead of at random intervals.

[BBDirtbiking]

This is so weird, so I connected a wire up to it, and put it back in the car. Well, all my lights were on before I had even turned the key in two clicks, or in the ignition at all... Well once the car was on, everything was great! The Tach worked, everything. Well, I go to shut off car and nothing. I can turn back ignition all the way and pull the key out and it would still be on. Only way I could turn it off was unplugging the yellow set of wires... This makes me think, how the hell is my car wired that my ignition doesn't work when that was plugged in.

I later cut the wire I had put in there earlier, put the gauges back in and everything worked, so I am just dumb founded...

Does ANYONE know where I can get a electrical diagram for this car?! It would help me immensely.