PV: Rev counter for PV 544 with a B18

[Gigahertz2706]

Hey, I have tried searching the web, but I was unable to find anything definitive.
My father owns a PV 544 with a B18. He has tried to install a rev counter before, but the ones he had bought, didn't work. So I wanted to give him one as a present for his birthday.
Problem is, I couldn't through research figure out how the rev counter would connect/work. I am not extremely knowledgeable in old cars, so I figured I would try and ask here.
I would appreciate any help in what kind of aftermarket rev counter may work.

[Rustinmotion]

Originally Posted by Gigahertz2706

Hey, I have tried searching the web, but I was unable to find anything definitive.
My father owns a PV 544 with a B18. He has tried to install a rev counter before, but the ones he had bought, didn't work. So I wanted to give him one as a present for his birthday.
Problem is, I couldn't through research figure out how the rev counter would connect/work. I am not extremely knowledgeable in old cars, so I figured I would try and ask here.
I would appreciate any help in what kind of aftermarket rev counter may work.

It depends on the rev counter, most modern ones use the negative coil connection as the signal and would have 4 wires
Switched 12v
Negative earth
Signal from coil negative
One from instrument lights


I know the early Volvo ones had to be wired in series between the coil negative and distributor see photo

[142 Guy]

Rustinmotion has it pretty much summarized. The traditional Smiths tach which Volvo used right up to the end of the 140 and 1800 production (mid '70s) was a current sensing tachometer wired in series between the ignition points and the negative terminal on the coil. From my brief fling with a Smiths current sensing tach on my 142 I seem to recall that the polarity of the current sensing line is important. If your dad is trying to make a current sensing tach work, have him try switching the current sensing leads. This provides all the information you need to know about the Smith's current sensing tach.
https://www.sw-em.com/Smith's%20Tachometer.htm

If your Dad or you purchase a brand new tach you need to make sure that it is a tach meant for use with a distributor ignition system. 20 years ago that was not an issue; but, these days a lot of tachs pick up the engine RPM signal via a CAN data bus which is definitely not going to work with 99.999% of PV544s. A brand new tach meant for use with a distributor based ignition system will almost invariably be a voltage sensing tach which connects directly to the ignition points terminal (negative terminal of the coil). Smiths does make new tachometers (kind of expensive); but

https://www.merlinmotorsport.co.uk/p...saAoAwEALw_wcB

they are voltage sensing, not current sensing. Voltage sensing should work just fine and you should be able to find a nice one for $100 - $150. Go to a vendor that sells stuff for sports cars and tell them you want a tach for a four cylinder engine with conventional distributor. They should be able to fix you up just fine.

[Derek UK]

Have you got any Swedish contacts?
https://www.biltema.no/en-no/car---m...gue-2000047237
There is a wiring diagram on the documents.

[Gigahertz2706]

Originally Posted by 142 Guy

Voltage sensing should work just fine and you should be able to find a nice one for $100 - $150. Go to a vendor that sells stuff for sports cars and tell them you want a tach for a four cylinder engine with conventional distributor. They should be able to fix you up just fine.

I don't know about any store like that near here, the closest there is, is the one Derek UK referred to below. But they are not specialized nor of high quality.

Originally Posted by Derek UK

Have you got any Swedish contacts?
https://www.biltema.no/en-no/car---m...gue-2000047237
There is a wiring diagram on the documents.

He has tried this one, but apparently it did not work. With that said, I don't know what exactly he has tried or what precisely the problem with the previous rev counters were.

I have tried to search more with the new information you guys have given me, but I still have trouble finding one which definitely should work.
If I am unable to figure this out without the knowledge of what my father has done/tried, I will ask him and work with him to make this work, although I would prefer it to stay a surprise.

Thanks for the help guys, also you Rustinmotion.

[Rustinmotion]

Originally Posted by Derek UK

Have you got any Swedish contacts?
https://www.biltema.no/en-no/car---m...gue-2000047237
There is a wiring diagram on the documents.

Ah Biltima, ikea for cars, many happy memories
Orange is the supply for lights and red is for ignition

[Rustinmotion]

Originally Posted by Gigahertz2706

I don't know about any store like that near here, the closest there is, is the one Derek UK referred to below. But they are not specialized nor of high quality.


He has tried this one, but apparently it did not work. With that said, I don't know what exactly he has tried or what precisely the problem with the previous rev counters were.

I have tried to search more with the new information you guys have given me, but I still have trouble finding one which definitely should work.
If I am unable to figure this out without the knowledge of what my father has done/tried, I will ask him and work with him to make this work, although I would prefer it to stay a surprise.

Thanks for the help guys, also you Rustinmotion.

If it’s a dash top mount your looking for search eBay for “TIM Electronic Rev Counter Tachometer With Dash Mounting Pod”, I have exact same and it’s a good match for the interior

[142 Guy]

That Biltema tach should work. Because it is meant for operation with 2, 3, 4, 5,6 or 8 cylinder cars, there has to be a cylinder setting or a configuration procedure at start up in order to get the correct display. If this is a case that the tach needle is completely failing to move, then that sounds like a wiring issue and changing to a different tach is not going to fix that. Use a voltmeter to confirm that the switched +12v is actually energized and that the ground is solidly connected to the chassis.

[Gigahertz2706]

Originally Posted by 142 Guy

That Biltema tach should work.

I just asked him, and it doesn't fit. He said it's "digital"? So it seems like some aftermarket distributor, don't know what the digital part would mean though.

[Rustinmotion]

Originally Posted by Gigahertz2706

I just asked him, and it doesn't fit. He said it's "digital"? So it seems like some aftermarket distributor, don't know what the digital part would mean though.

If it has a traditional coil it should work, I’m using a 123 ignition and the tach works fine