Tachometer Functioning incorrectly

[Miffanwee]

Hi All,
When I first bought my Vanagon 1.9 petrol Westy my Tachometer was working intermittently, now after 2 years, it no longer works at all.

However..... When I turn the ignition on the Tacho needle rushes round all the way clockwise and STAYS at MAX (see attached photo "Ignition ON")

Ignition ON.jpg

Thus obscuring the Fuel gauge reading...annoying.

When I turn the ignition off, the needles drops back to its start position on bottom left. (see attached photo "Ignition OFF")

Ignition OFF.jpg

I have taken the Cluster off and checked all the BLUE foil for nasty tears...nothing, in fact looks in excellent condition.
I tighten the brass nuts up....no difference.

Do you think I maybe looking in the wrong place?
How about if I tried at the engine end of things????
So question.... What am I looking for at the engine connection end???

Does it feed off the coil or what?

I havent checked anything with an electrical tester, I dont know where to start with that.

Also I would like to mention that the FUEL and TEMP guage work perfectly normally.....which is nice.
Although the Digital Clock has a mind of its own!
Thanks

[Miffanwee]

Sorry for the bump, but could do with some help really.
44 views and no reply, am I breaking forum rules by asking obviously stupid questions?
I have trawled through wiki, read up on the Bentley manual, read through other people's troubles as much as I can get away with in one working day.....

I have done more under the bonnet work tonight and detached ALL the wires from the coil, individually and turned the ignition on without cranking engine, only to find that it made NO difference to the rev counter gauge, which leads me to believe that it must be the actual Tachometer.

One question I have...... The voltage regulator that is on the Blue foil network, can that effect the tachometer?

I only ask because I have a fuel gauge that is a tad inaccurate tbh, it drops like a stone when under half a tank and going up and down hills just had a mind of its own....is that natural / red herring????
I have already replaced the petrol tank sender, expecting more accuracy to no avail.

Thanks

[tonytech]

No rules broken, I think we are all as stumped as you.

I would continue looking at the instrument cluster, perhaps the earth to the counter if it has one.
or possibly the rev counter itself is U/S.
T

[Dave307]

^^^^^^^^
Think people are stumped I've asked loads of mates and no one has any idea. Sorry.
I have to say I'm surprised no one has seen it before.

[Smcknighty]

Temperature is off the scale isn't it - is that normal for you?

[Smcknighty]

Ignore that - I'm guessing that is the cold end as its the same in both photos. The voltage regulator when it doesn't work makes the temp gauge overread and also the fuel tank I think

[Miffanwee]

Aha you talking about the pictures????
Not the temp works fine, those pictures were taken with ignition key turned on, and instant picture, on a cold engine, not running.
Temp gauge works fine and when fan kicks in drops fine too. No probs there I believe

[Miffanwee]

Must admit, I looked at the regulator and doesn't look dark in places as I read it could be if burnt out.
I really am stumped

[Smcknighty]

So.. At this point if I were you I'd be reading up on how these things work and trying to create some kind of test to make sure the individual bits actually work. Are you based near anyone who has the same dash and might swap? This sounds like its either a feed problem or a problem with the unit I guess as its going straight up and staying there it 'possibly' is fooked or the feed in is giving a funny signal. Could try disabling it completely?

My gut is unless you get lucky and find someone who has had the exact same problem you are stuck..

[Miffanwee]

Yes I was thinking that.
Funny I went out to walk the dog and passed an old air cooled transporter, knocked on his door had a chat and he thinks he might have a spare cluster kicking around.
So I thought of swapping it over just to see if I get the same.
He's having a search, in the meantime I will be looking for faulty earths under the dash next.

[Miffanwee]

RATS!!!!!
Really thought I had fixed it then.....took the fuse box out and removed every earth from the 2 crowns.
Replaced 2 spade connectors as they had broken.
Put it all back, turned the key....bam! Rev counter still springs round all the way.

[Miffanwee]

Mystery connections at back of blue foil.
I am guessing that they would / should connect to a clock IF it was fitted instead of the tacho?

IMG_0281.jpg

Also these foil connectors look brand new!

IMG_0283.jpg

I can hear a little rattle inside the tacho as I move it, I think something is loose inside???
I want to take it apart but I am afraid of the blue foil getting damaged.

[Smcknighty]

I reckon wait and see what you get from that other fella. Mine was in a shocking state when I got it - I'd said probably because someone opened it up - the 30 yr old plastic seems to break pretty easily. You might find its not a problem with the cluster still?

[Miffanwee]

how did you fix yours then if it was in a shocking state?

[Smcknighty]

It's held together with:
Glue
Electricians tape
Luck

When I drive over too many bumps the temp gauge stops working until I whack the side of the dash

If its mostly not broke dont try to fix it..