Nothing works :-(

[SRK]

Well I replaced by alternator and now my tack and all instruments are dead and the ignition light is still on. I had labeled all wires and put them back exactly as they came off but obviously something is wrong. The schematic shows a ground wire which I do not have. Is there suppose to be one? Also, the rebuilt alternator I received from the internet had a sharpie line (like a negative) on the opposite terminal than the negative embossed on the alternator casing. Could it be that the rebuilder ran the negative to a different terminal and marked it with a sharpie? Would really appreciate any help or ideas anyone might have. I thought about just flipping the wires but felt I should ask the experts first.

Thanks in advance!!!

Steve

[angelw]

Hello Steve,
There are various reason why the gauges are not working but with regards to the ignition light being on is concerned, it will due to the Alternator not working correctly (not charging), or the Voltage regulator is faulty, or not adjusted correctly (there is a potentiometer accessible by removing the grub screw in the Left Hand end of the face of the housing).

The Alternator needs to be excited to start. This is accomplished by supplying 12V to it via the Ignition Light circuit (the filament of the Ignition Warning Globe is in this circuit), through the terminal connection of the Voltage Regulator. On being excited by the 12V supply, the Alternator outputs a charge back to the Voltage Regulator and when the voltage received on the wire from the Ignition Warning Light is in excess of the 12V it supplied, the Ignition Warning Light will be extinguished. If the voltage is hovering around 12V, then you will see the Ignition Warning Light just faintly glowing. Clearly, you have 12V to the Ignition Light; you then have to establish that the 12V is present in that same circuit at the Voltage Regulator. Without this 12V, the Alternator will not start charging and therefore, the Ignition Light will stay on.

The first thing you should do is test both the Alternator and Voltage Regulator for proper function. The testing of both these devices is well explained in the S3 E-Type Repair manual. If you don't have a copy, come back to the Forum and I, or other members will explain how its done.

Regards,

Bill

[SRK]

Bill, thanks for the explanation of how it all works. This is all very weird to me but I tested the alternator with a clip on ampmeter and it was reading essentially 0, tested the VR and it was reading 1.5v. (using the procedure in the manual) I have a spare VR so I tried it and nothing different. Decided to flip the wires and everything started to work. All OK for about 10 minutes of running and then it blew a 35A fuse. I decided to put the wires back to how it was on my original alternator and with a new fuse everything is now working. I've run the engine for about an hour with varying loads with no issues. The ampmeter reads between 45 and 65 most of the time. (for a while it must have been charging the battery)

I'm very glad that 40+ years ago I decided to get my degree in mechanical engineering since its very obvious I will never understand this electrical stuff!!!

Steve