Economy gauge erratic

[rob101]

Are you sure? I thought it worked of manifold vacuum.

well it certainly doesn't act like one, otherwise i am surprised to find that my car has the same vacuum in the manifold at idle as it does on full throttle it has to combine the speed reading with either vacuum (which i don't think it does because there is no MAF sensor in the manifold or vacuum line going to the cluster AFAIK) or a fuel injector duty. so my meaning is if you think its going to act like a normal VK commodore or similar vacuum gauge you will think its broken when it is operating normally.

[mamilapon]

That's one more thing i know now about E34's!!

[genphreak]

Driving along today and the economy gauge needle is just doing whatever it wants. Under acceleration it would start to read where it should, then just start moving from full left to so far right it disappears. Any ideas or past experience ? John '89 535is, Sydney

If the engine is behaving normally whilst the gauge is haywire, its in the dash or the feed signal it gets. Sure it could be the capacitors dying out but I would think others here would have noticed it happen before you John. Check your dash connectors are clean (a wipe with ispropyl alcohol) and check also the loom connectors, if someone has installed an alarm or other device they may have 'tapped into 12V' in the wrong place... it really sounds like a bodgey connection or a poor wiring job- but it is easy to pull the gauge panel so perhaps a resolder of all the joints on its PCB would yield a result also... good luck- and let us know how you get on...