E30 Zone

Hi,

My mpg gauge shows 0 when accelerator is pressed then swings to 50 mpg when depressed i.e. doesn't stay anywhere in the middle and the SI Board doesn't light up. After 1 - 2 hours driving the si lights flash a couple of times & then both work perfectly. The batteries on the SI Board are the lithium type. All other gauges are fine. Any ideas of the problem?

Thanks.

Bump

The MPG gauge (energy control) is doing this because it isn't processing road speed data.
In the one case of this I've come across, many years ago, I found a burnt resistor on the speedo circuit board and a transistor that had been blown apart on the SI board, and at this point stopped investigating further and simply replaced the lot.
This can't be the case with yours since it's intermittent, but it could be a case of a poor connection in the signal path. Check the soldering of the pins of the plug on the speedo. circuit board and the SI board for dry joints, but if that draws a blank, you should try a different SI board.
Might be worth checking the voltage of the lithium batteries.