'84 240 tach

I just installed a large tach (that I bought cheap on ebay) into the
cluster on my 84 245. It works, but the needle only gets up to zero when
it's actually running at about 1200-1500 rpm. Is there any calibration
available on this tach? Is it possible to pull the needle off and
replace it in a different position?

Thanks
Tom

 

Tom,

Tachs are made differently for 4, 6 and 8-cylinder cars. I suggest you
hit the mfr's website and determine whether yours is user adjustable.
Otherwise, an instrument repair shop should be able to help you.

 

I should have been more clear.

My car is a 1984 Volvo 245 non-turbo which came from the factory with
the large clock installed in the cluster instead of a tachometer. The
tach came out of a 1984 Volvo 240 turbo. Both are 4 cylinder 1984 Volvo
240's.

When the car is not running, the tach needle registers well below the
zero mark on the scale. When it's idling, the tach needle moves up to
just below the zero mark. When I rev the engine, the needle moves up
apropiately

I haven't yet checked it against my dwell/tach meter to see exactly how
much it's off, but it seems to be zeroing problem. Do you know if the
needle is splined or press-fit on it's shaft? If so, I should be able to
pull the needle off and re-install it in the zero postition with the car
not running. Perhaps when the tach was removed from it's original car,
the needle came off and was put back on in the wrong position.

I just thought someone on here might know. I don't want to pull it out
of the instrument cluster and break it trying to find out.

 

Were it *my* instrument, I would remove it from the cluster and trudge
off to an instrument shop. But that's me. Perhaps you're more
adventurous.

 

Well, since it's *my* instrument (I paid a less than 12 bucks for it)
and the nearest instrument shop is at least 110 miles away from my
humble home in southeastern Oklahoma, I think I may just make the "okie
choice" and try to fix it, or live with it. I suppose if I break the
needle off I can JB Weld a toothpick on there pointing toward the zero.
If I do that, I promise to paint the toothpick orange.

Thanks,
Tom

 

Before you do that, might I suggest you inquire of maybe IPD,
www.ipdusa.com as to what might be the issue. I would hate to see you
bugger up the instrument only to find there's a simple solution. Their
guys are pretty smart.

OTOH, ya got twelve bucks in the sucker so what the...

 

First, verify where the needle sits when the car is off. If the needle sits
on zero until the switch is turned on the problem is electrical rather than
mechanical. There are likely to be two electrical adjustments: one for zero
set and one for calibration. They are almost certainly not marked like that.
You can try adjusting either adjustment (assuming you don't see more than
two) by carefully marking or noting the exact position of the adjustment and
turning it one way and the other. If that didn't have the desired effect set
it back to the original setting and repeat with the other.

Most needles are press fit onto the shaft. I haven't seen one that was
cemented on, but some are so tight it can make you wonder. Getting it off
takes care and a bit of patience (unless you have the slick tool) with a
pair of blades on each side and even prying pressure. You can try using your
fingernails in a pinching fashion but they are usually pretty tight for
that. Putting it back on is easier - press it on gently and verify the
needle is zeroed, then push with your fingertip to seat it. Never tap on the
needle to seat it as the other end is typically in a garnet jewel that can
be broken by impact.

For smaller adjustments, look just under the face at the top of the meter
movement. The upper spring is normally fastened to a moveable plate with a
tab bent so the plate can be rotated to zero the meter. It doesn't have a
lot of range so I doubt it will fix your basic problem. Makes me wonder how
it ended up so far off, though.

Mike

 

That's the way I figured it. I just remembered that Dave Barton's
website offers those white-faced gauge dials, so I went there and found
very detailed instructions on how to get the needle off and back on. I
think I'll just pull it back out, zero the needle and see how it
compares to the dwell/tach. Since this car is NA and has 24 years and
240,000 miles on it, I doubt I'll be going anywhere near the redline
even when passing all the oilfield trucks that clog up the mountain
roads around here. But the clock was broken anyway so it was worth a shot.

Thanks (and thanks to Dave Barton)
Tom

 

Thanks, Mike. I'll pull it back out and see what I can do with it. Great
information there. Just what I was looking for.

Tom

 

@ Michael:

You seem to know a lot about these instruments: Do you (or anyone else) know
if Volvo provides a tach for a 240 with a DIESEL engine?
I have a tach in my instrument now, but it is not functional because it came
from a non-diesel car.

 

Sorry - my knowledge doesn't come from Volvo tachs as such but from being
enlisted for a while to help in an aviation instrument shop back when I was
an avionics tech.

Any diesel guys know about this?

Mike

 

This may or may not be of any help. In 1984 I outfitted a new 240D
with a full set of VDO gauges and considered adding a tach. At the
time VDO made a tach for the 240d. Whether they do now is unknown.
Consider calling VDO.

 

I just pulled the tach out and gently pulled on the needle hub. The
needle came off with hardly any effort at all. When I gently but firmly
pushed it on again (pointing at zero) it seemed to be more tightly
attached than it was initially. Seems to me that this wasn't the first
time the needle had been off, so my theory that it had come off and been
put back on in a different position may have been correct. I checked it
against the dwell/tach meter and it's reasonably in compliance up to the
3000 rpm limit on the dwell meter. Who knows how accurate the meter is.

Anyway, It's another victory for Okie Engineering. If it ain't broke,
don't fix it. If it IS broke, ya got nuthin' to lose.

Thanks to All

Tom

 

Sometimes we miss the obvious and simple solutions....congratulations!

 

All the cars that this tach will fit came with 4 cylinder engines.

There is an adjustment pot in the tach as I recall, it's possible you have a
fault though like a cracked solder joint on the circuit board, unless
someone twiddled with it these don't tend to go out of calibration.

 

Why would you take a 23 year old tach to an instrument repair shop? One
could probably buy 3 or 4 working ones for the cost of having one repaired.

 

There was one available, it may even be the same guage. Some Diesel cars
used a mechanical cable driven tach, but it was not uncommon for there to be
a magnetic pickup or similar electrical device to provide a tach signal from
the engine. Unfortunately I'm not familiar with these motors, I've only ever
seen two of them and they were both in 700 series cars, which both did have
tachometers.

 

dont know about your tacho but if its like my wifes speedo needle it came
off easy and now reads 5 klm faster than the car is actually going with no
more tickets .Some like to nudge the limit some like to shove the limit .

 

_____
Yes, a 240D tach was/is available. I installed one on a 1984 240 diesel
wagon. Its signal comes from the alternator. It is NOT the same tach
as the one for the 4 cyl petrol engine. One has to run the signal line
as part of the installation process.

 

Yes, a 240D tach was/is available. I installed one on a 1984 240 diesel

Great! Thank you for that information
I looked at my alternator and found that it is at BOSCH (don't know if you
use them in the U.S.). It has an unused output that is signed "W". Could
that be for the tach-signal maybe...?