94 Disco Tach problems

[Nadir(Detroit)]

Hey everyone,
I have a 94 discovery with a tach that has a mind of its own. I know they seem to go dead when you have a bad alternator, but I recently replaced my alternator, and the problem just started. The tachometer works sometimes, but other times it starts bouncing all over the place. Could this be from a bad ground? My interior lights also seem to flicker at times, but the alternator is working properly. Any suggestions on how to fix this problem(s) would be appreciated.

Thanks!
Nadir Ali

 

[RoverChic]

If I were you I would try this first: Check your grounds. There is a ground cable
going from the top bolt of the starter, straight over to the frame.
Specifically, it is on a body mount bracket. Pull that nut and bolt, clean the
cable end and bracket where the cable end contacts it. You have to clean it
real well. So it's shiny metal...I was told to do this and it *helped* my problem some what. I had a bouncy tach too..It was not my alt/battery.
Melissa
1998 D1

 

[Nadir(Detroit)]

Thanks a lot Melissa. I checked under the hood and saw the ground wire you were talking about. 2 things, first, the wire was cut, can you tell me the stock grounding location? And 2, the wire was extremely thin, i'd say about 20 gauge, is that how the stock wire is, or could it be a cheap replacement from the previous owner. I appreciate any answers.

Thanks!
Nadir

 

[discojoe]

The small (I mean really small) wire is the tach lead. If it's broken splice it back. Also tighten the connector that pushes on the spade post on the back of the alt. This should fix the tach.

I suggest a voltmeter/compass mounted just above the t'case shift lever (spliced in to ther cigar lighter). Discos need the charging system monitored as most of us use rebuilds some of which last only for days.

Good Luck

 

[wturner]

I got a brand new alternator once and the tach was bouncing and the lights were flickering too. I had three different places test the alt. and all said it was fine. I sent it back for an exchange anyway and the next new alternator fixed the problem. You could just have a faulty new alternator that still somehow passed tests like I had.

 

[RoverChic]

Hey Nadir, I am with wturner on that one..might want to check your alt too. Should put out about 14v or mine is about 13.80v which is "normal" under load. I am considering replacing mine soon as I have a feeling it needs to be replaced. Good Luck, Melissa 1998 D1 78K miles