Christmas Dash Lights, but no Electrical Problem

[oab_au]

Originally Posted by TomsSVX

+1 to the short. I had dealt with the same problem. Regulator gave up the ghost and within 5 mins of driving fried over half a dozen modules.
Tom

Tom this bit is starting to make sense. The regulator in the alt has a ‘Diagnostic & Warning Circuit’ that operates the ‘Change Light’ to warn of problems. For some unknown reason (maybe they just wanted them to be noticed) they have used a few diodes to have the ‘Stop light check’, Parking brake light’, ‘Charge light’, and the ‘’Steering Warning light’ all coming on.
The book says that the Diagnostic system will warn of these problems;
No voltage generated.
Excessive output.
Terminal B disconnected.
Terminal S disconnected.
I think that there is a system of ways that the regulator brings these lights on, to signal the type of trouble. On at idle, going off when you rev it. Off at idle, going on when you rev it, and flashing them. I also think that the flashing is the ‘Excessive output’ warning.

When the regulator has a problem that prevents it from controlling the output, the alternator charges flat out, its voltage only held to the rising battery voltage. This would have the fusible link carrying excessive current for an extended period of time. Finally the link blows out. When this happens the alternator is on full change, about 90 amps at 15 to 16 volts, 15.5 X 90 equals about 1390 watts, suddenly the link opens, and the amperage falls to zero. Now we have 1390 watts divided by 0 amps equals 1390 volts.

This would not worry any thing if the alternator was isolated by the fusible link, but there are a number of circuits still connected to the alternator, that will have to dissipate this high voltage. As there is quite a lot of energy in the alternator, all the circuits that are still connected, will take quite a few milliseconds to dissipate it. The circuits that will suffer the most are, the low resistance circuits, any relays that are on at the time will have the points welded together.

Harvey.