D1 - Tachometer Non-Functional, Jumps with Headlights

_ExpeditionMan

Well-known member
Dec 11, 2017
295
34
Texas
All,

I have an interesting question for you today. My 1996 D1 (5spd) is currently experiencing an issue where my tach does not work at all. At idle, in gear, I do not see any movement regardless. However, when I turn the light stalk to parking lights the needle jumps to just below 1000 RPM and stays there. If I turn the lights on all the way the needle jumps to ~1300 RPM and sits there. Turn them off and it returns to zero. I can cycle it at will with the light switch, but it has no relation to actual engine RPM.

I have an ultragauge hooked up to the OBD2 port and the idle signal it receives seems accurate, which suggests the issue is not with the ECU. From my research (on this forum) it appears most tachometer issues in the D1 are related to a failing alternator since that is where the signal originates from, however since the ultragauge sees a good value I doubt this.

Anyone have any ideas about what to do besides check the cables coming off the alternator?
 

robertf

Well-known member
Jan 22, 2006
4,778
354
-
ECU does not get engine speed from the alternator, only the gauge does that. Check the wires, then check alternator itself.
 

p m

Administrator
Staff member
Apr 19, 2004
15,617
837
58
La Jolla, CA
www.3rj.org
Alternator or its wiring.
Replying to myself here, with an observation.
On my 353-kmi Classic, the tachometer started flaking out, and then died altogether.
My natural reaction was to swap the alternator - which didn't fix the tach issue.
The alternator put out solid 14V at idle, and I measured ~16VAC at the terminal on the alternator that feeds the tach.
Got to it last Saturday. Confirmed wire continuity from the alternator to the instrument panel.

Fortunately, a friendly indy shop nearby was open on Sat. and had a used 95RRC instrument panel to play with.
Hooked it up - boom, everything working.
I resisted the temptation to swap the entire panel (the replacement would have almost exactly 200kmi less on the odometer), so I kept my speedometer/odometer but used the rest of the replacement unit.

I read someplace that the add-on board in the back of the instrument panel; swapping the add-on board didn't do the trick - it was the tachometer itself.
 

terryjm1

Well-known member
Jan 23, 2011
1,486
375
My tach intermittently quits working. It always works at start up but after 5 or 10 minutes it quits working for short spells. Conventional wisdom was it was a bad connection at the alternator. I disconnected and reconnected it. No improvement. So, as my alternator came with the TDI engine and obviously was very old with an unknown history, I thought maybe it was the problem. I had a new one I planned to one day swap anyway, so I did. It changed nothing. Also, my speedometer does the same intermittent failure, but not when the tachometer acts up. They never do it at the same time. I thought it was the speedo sensor until the tach started acting up. Now I wonder if the problem is connected.

I have two spare gauge clusters. I’m wondering if the problem could be in the cluster electronics. Any thoughts?

FWIW - the D1 and tachometer only have about 71,000 miles.
 

p m

Administrator
Staff member
Apr 19, 2004
15,617
837
58
La Jolla, CA
www.3rj.org
Very likely so. Unfortunately, to the day I found zero info as far as detailed schematics of Land Rover instrument cluster and add-on board. I would love to reverse-engineer at least some of that, maybe I'll find something if I look at the boards of my ex-cluster with a magnifying lens.
It is easy to interchange the gauges in these clusters - you have to
(a) get the cluster out of the binnacle (easier on the D1 than on a soft-dash Classic),
(b) pop seven spring clips holding the glass and its frame to the instruments - three on one side and four - on the other, and
(c) take out several screws holding a particular gauge to the cluster.
The gauge just falls out, and you can replace it with whatever you got from the _other_ cluster.
 
  • Like
Reactions: terryjm1

Lake_Bueller

Well-known member
Aug 11, 2004
2,105
59
56
Beloit, WI
Have you recently replaced the serp belt? Surprisingly, there is more than one way to route the belt. But it will cause funny tach & speedo errors when not routed correctly (been there, done that)
 
  • Like
Reactions: terryjm1

p m

Administrator
Staff member
Apr 19, 2004
15,617
837
58
La Jolla, CA
www.3rj.org
Have you recently replaced the serp belt? Surprisingly, there is more than one way to route the belt. But it will cause funny tach & speedo errors when not routed correctly (been there, done that)
Definitely not me. Not to say I couldn't fuck that up, just so I've done it a lot of times.
And it has to have zero bearing on the speedo readings - in a D1 it is fed from a t-case-mounted VSS.