Hello all, My 75 has the optional Volvo R-Sport instrument cluster. The tach is not accurate, it reads double the actual rpm.

I pulled the dash apart, thinking I would find an adjustable cylinder selection switch like aftermarket tachs, no such luck.

Anyone have any ideas how i can fix this?

TIA

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Bruce S. near D.C.

Thanks for all of the replies, my tach is marked 4zyl/4takt.

I guess I'll take Gambit's advise and pop it open and see what's in there.

Thanks again,
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Bruce S. near D.C.

Long ago when I had an '78 I wanted a tach. The only ones I could find were in the 260s models. None of the 240s in that era and area had a blasted tach!

So, I risked $10US and bought one of the 262 tachs. I carefully removed the case and found to my delight, a POT inside.

I hooked up my old Craftsman Penske Engine Diagnostic Tool, (you know, the one with the 1 1/2 foot dail), set it up for RPMs and on the hood and calibrated the Volvo tach to what the Penske said and viola!

Could very well be that your tach has a POT inside as well.

Gambit...

Probably right, does "6 zyl" or "6 tacht" appear on the silver case? I have a couple of spare 4 zyl tachs.

Your post made me a little curious about my 74 R-Sport cluster. I haven't yet made the dash adapter to get it in to my 81 Turbo, so I don't know if it works properly yet, but the tach has "6 Zyl./4 Takt" stamped into the case. I always assumed it was a 6 Cylinder tach, but wondered about the 4.
Am I missing something?
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1981 242GLTi (finally did that Blower Motor!) 1967.5 122S Automatic (tempermental)

No, I think I am. I guess it is only the 4 or 6 zyl. that counts, and the other thing which can translate as clock, is not related to cylinders. But I am sure yours is for a 6 cylinder.

Thanks for clearing thigs up. I had a vague hope that the 4Takt would prove to be more imprtant that it is. Guess someday I'll have to get serious about putting this in my car and find a 4Zyl/4Takt.
Thanks.
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1981 242GLTi (finally did that Blower Motor!) 1967.5 122S Automatic (tempermental)

"6 Zyl./4 Takt" = "6 cylinders/4 stroke"
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My 240 Page

IS it possible you've got a tach intended for a 164?
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Rob Bareiss, New London CT ::: '87 244DL/M47- 221K, 88 744GLE- 202K, 91 244 181K, 88 244GL 145K