Testing an instrument panel

[nthomas1]

Can anybody tell me if it's possible to test the instruments in a Fulvia Series 2 Coupe instrument panel when it is not installed in the car?  The rev counter in the panel that is installed in my car does not work properly.  It stutters around low revs even when the engine is clearly revved higher.  The car is now in a stripped down state so I can do no "live" fault finding at this time. 

The car came with a spare instrument panel but I do not know if its instruments work correctly.  I'm wondering if the spare panel could be tested - either by me, or by an instrument specialist.  Or maybe just the rev counter in the spare panel could be tested and, if ok, installed to replace the one currently in the car.  I've attached pictures of both panels. As always, I'd appreciate any pointers on this.

[frankxhv773t]

You don't seem to be getting any immediate response on this so I will offer my two pennyworth. The rev counter seems to be electrical rather than mechanically driven. That would mean it picks up electrical impulses from the ignition system and uses them to deflect the needle. You would need to work out if the problem is with the signal or inside the unit. Could you connect it with a long wire to the output from another Fulvia to see if the supply of the electrical impulse is the problem and whether your spare works?

[lancialulu]

I will add.... these panels can be tested by a competent electronic engineer with voltage source and a pulse generator for the tacho. Generally it will be a poor earth somewhere else so check those first (difficult on a car in restoration.

[nthomas1]

Thank you Tim and Frank for the pointers.  For a competent electronics engineer should I look for a car instrument specialist?

[frankxhv773t]

You may not find an automotive instrument specialist locally but Speedograph Richfield Ltd have had good write ups in Classic car magazines. I would be strongly tempted though to clean up all the connections and try powering the rev counter off another, running car.
 

[JohnMillham]

You may not find an automotive instrument specialist locally but Speedograph Richfield Ltd have had good write ups in Classic car magazines. I would be strongly tempted though to clean up all the connections and try powering the rev counter off another, running car.
 

If you use Speedograph Richfields, make sure they insure your items. They lost my Augusta Metron clock! Regards, John

[nthomas1]

Thank you Frank and John for the tips.

[Jaydub]

Rev counter is pulsed by the ignition coil via the green/black wire from the negative side of the coil to a red block connector( 8 terminals) behind the dash, and then to the instrument. Make sure the connectors are not corroded or loose. Check continuity and resistance with an ohmeter if you can access one, between the coil and the block connector, and block connector to the instrument. As previously suggested make sure the earth connection is good and that there is a 12 volt feed to the positive terminal on the instrument ( red wire). If they are all correct then test the instrument by making up some jumper leads, apply a 12 volt feed, an earth and pick up a pulse from the negative side of the coil on another car as previously suggested.
Failing that, I always use Speedy Cables, Swansea for instrument repairs. Tel. 01639 732300.

Good Luck.

[nthomas1]

Great - that's just the information I was looking for. Many thanks.

[stanley sweet]

Just what I need to know too. Sometimes my tacho behaves perfectly, sometimes it swings wildly around.

[Jaydub]

Just a quick addition to my previous post on rev counter testing. I said the pulse comes from the negative terminal of the coil which is true of a negative earth car but it will be the positive terminal on a positive earth car of course i.e. distributor side of coil. As I know very little about Lancias I thought I had better clarify that point as there will probably be some positive earth cars that you are testing.