diesel tachometer?

[PanosRs]

Hi!!! My diesel pickup have a big clock an i want to put in it a tachometer... does the instrument cluster from a petrol felicia work on a diesel?????

[RicardoM]

No. They are not interchangeable, You would have to make quite a few modifications on the PCB. The easiest and the cheapest would be to buy an instrument cluster from a scrapped Felicia 1.9D GLX.

[PanosRs]

Here in Greece the diesels are rare... only petrols in scrapyards...

[KenONeill]

Even if the PCBs were directly interchangable, a petrol tacho isn't really suitable for a diesel due to the difference in peak engine speeds.

[RicardoM]

Here in Greece the diesels are rare... only petrols in scrapyards...

Oh yeah... I remember reading somewhere there are tough regulations for Diesel cars in Greece.

 

So how skilled are you with basic electronics? In case I tell you how to adapt a petrol dash to your car.

[PanosRs]

I have a frient who can do that job...

[RicardoM]

I recommend getting an instrument cluster from a Felicia 1.3 MPI or 1.6 manufactured after 01.1998 (Felicia II with facelift) Here is what might expect if you install it directly, without any modification:

• incorrect temperature indication
• incorrect fuel quantity indication
• no warning buzzer when lights left on
• erratic tachometer indication or not working at all

The most dangerous part if the instrument cluster is connected directly is the last one because the integrated circuit (IC for short) that drives the tachometer gauge might get burned. On 1.3 and 1.6 MPI, the ECU feeds TTL impulses (5V amplitude) to input connector on PCB (pin 7, yellow/green wire, yellow connector). Diesel engines feed up to 12V amplitude impulses from the alternator (pin marked W) so without a modified voltage divider the IC might fail.

 

It is not big deal to do the modifications if you have a multimeter, a proper soldering iron and a steady hand. The PCB is one side, through hole technology, so easy to work with.

 

Even if the PCBs were directly interchangable, a petrol tacho isn't really suitable for a diesel due to the difference in peak engine speeds.

Ken is right. The tachometer dial for Diesel cars goes from 0 to 5500 rpm. On petrol cars the dial goes from 0 to 7000 rpm. In other words, on a Diesel car the tachometer needle will stay mostly in the first half of the dial on normal driving. If that is OK with you, then you can get a known good instrument cluster as mentioned at the beginning of this message. We'll continue when you have it.

 

PS

If any member of BriSkoda has a Felicia Diesel with tachometer and is willing to take a few high resolution photos of the instrument cluster's back side (the components side and the routes side of PCB) then things will be easier for our newbie.

Edited 4 November, 2015 by RicardoM

[PanosRs]

Thank you all for your time!!!!!!!

[TeflonTom]

Its possible that your alternator may not have the required w terminal to drive a tacho if your car did not have a factory fitted rev counter, in which case you would need to take the alternator apart and solder a wire on to one of the 3 stator outputs before the rectiifier bridge and run that either direct to the cluster or tap into the loom elsewhere.

[RicardoM]

@TeflonTom

Tachometer or not, the ECU needs an engine speed input signal from pin W of the alternator (see wiring). Am I wrong?

 

Also, from my knowledge, every Felicia Diesel has the tacho signal wire already fitted to instrument cluster. Am I wrong?

 

@PanosRs

Please take a clear photo of the alternator (connectors side) then attach it here.

Edited 5 November, 2015 by RicardoM

[PanosRs]

it has the W pin on altenaton.. tomorow i will post a foto...( if i can do that..!!)

[RicardoM]

So in fact there is not such thing as alternators without W terminal on any Felicia Diesel.

[Substan]

I too have a 1.9 diesel pickup and im interested in converting a 1.3 petrol tacho to use on my diesel engine, if the conversion is possible please advise and finish your forum post, many thanks for accepting me as a member

[RicardoM]

Too bad the OP didn't update the topic. The conversion is definitely possible. Not plug and play but fairly easy to adapt it with guidance from me. What year/month is the donor car?

Edited 16 June, 2016 by RicardoM

[uma1998]

I have some diesel clocks with rev counter kicking about from my last breaker

[ThomasItis]

Just read this topic. Ricardo why this can't be done with a pre-f/l instrument panel?

[RicardoM]

Thomas,

I didn't say it can't be done using a Felicia I instrument panel. I recommended using a Felicia II instrument panel only because it needs less modifications. I noticed that very few members have basic electronics skills (measuring and soldering) so I tried to make things easier.

[ThomasItis]

Thomas,

I didn't say it can't be done using a Felicia I instrument panel. I recommended using a Felicia II instrument panel only because it needs less modifications. I noticed that very few members have basic electronics skills (measuring and soldering) so I tried to make things easier.

As always you are very helpful and thank you for that. I have a pre-f/l dash from 1.3 mpi (well a couple of them    ) and I am looking to do the mod to my 1.9 D pickup not for cosmetic reasons but I am in search with using different gearboxes and tyres in order to make it a little bit ''traveler'' without messing the towing and loading abilities, so reading rpm's will make my life easier. When you have free time send me a p.m. with the procedure. 

[RicardoM]

When you have free time send me a p.m. with the procedure. 

I've always advocated for sharing knowledge with everybody in public. That is the spirit of any forum where people need a little help.

 

It is nice you have several spare dashboards. That might come in handy if some components are faulty.

 

The first step I do is I look if there is a wire connected to pin 7 of yellow connector (see photo). Most often the wire is yellow but could be also green or yellow/green. Through this wire the rpm signal gets to the dashboard.

 

 

Having identified the colour of the wire, you need to trace it back to the alternator. Diesel cars get the rpm signal from the alternator. Carburettor cars get it from the ignition coil. MPi and SPi cars get it from ECU.

 

If you traced that wire coming out of the alternator, you're good. Take out the temp gauge and fuel gauge from your original dash and install them on a MPi dash. Connect the MPi dash (all bulbs must be installed and in good order) and without putting back all the covers (see photo), switch ignition key on but don't start the engine yet. Test all alert indicators, backlight, fuel gauge.

 

If everything is ok, start the engine. There is a slight chance the tachometer works right away. If not, you will need some more work to do. For now you have enough information. Keep me updated.

 

[ThomasItis]

The first and only time I tried to install the petrol dash to my diesel the only thing that happened was that the engine rpm gauge ''jumped'' a little bit and then died. Then I realized that something went wrong.... Just put the old part back and left as it was. Next step??

 

Edit: I forgot both times I opened and changed the dash to check for cable 7, but everything else worked fine except rpms. 

Edited 24 June, 2016 by ThomasItis

[RicardoM]

OK, that is valuable information. Better late than never. Hold on for now. I will elaborate later.

[Substan]

Appreciate getting back as for donor clock im not too sure but believe its from a 1.3 petrol, i understood from your forums that a petrol version uses a 5 volt signal input so i have fitted a 5 volt thyristor in line with the yellow/green signal wire however the tachometer still fails to operate but i have noticed movement on starting, is this due to the battery voltage reduction on initial start? I have also changed over the fuel and temperature gauges as suggested and these both work correctly

[Substan]

Sorry not thyristor rather 5v zenor diode, i should never try having a conversation whilst writing

[RicardoM]

Sorry not thyristor rather 5v zenor diode, i should never try having a conversation whilst writing

True. I was writing the promised answer about diesel dash conversion when I saw your "thyristor" solution. You saved me a question about it Although you are partially on the right track with the Zener diode trying to reduce the input signal amplitude to TTL level I will explain why this doesn't work.

[RicardoM]

Sorry for the delay but I had to study the dash conversion for Diesel cars more in depth. As you know I struggle to pass accurate information on this forum. In my country it's rare to find a Felicia with diesel engine so I had to scavenge the Internet for whatever piece of information I could get my hands on. Eventually I came across a few clear enough photos of the instrument cluster's PCB from a Felicia 1.9 GLX (with tachometer). That helped me a lot.

ThomasItis
Based on your testimony (rpm gauge "jumped" a little bit and then died) we now know for sure there is a wire coming from the alternator (pin W) to the PCB of instrument cluster from factory on every Felicia diesel. We also know there is an rpm signal coming through that wire. The problem is the shape, the frequency and the amplitude don't match the spare board(s) you have.

Before going to the juicy part of the conversion, we need to understand what type of tachometer input signals (TIS) are fed to pin 7 of yellow connector of the PCB.

There are three types of TIS depending on engine type:

• On 1.3 and 1.6 injection engines the raw signal from the crankshaft sensor is cleaned, processed and formatted by the ECU as square 5V (TTL)
• On a carburettor engine the square 12V signal present on pin 1 of the ignition coil is used
• On a diesel engine a variable amplitude sinusoidal signal coming from pin W of the alternator is used.

So the target is to convert a variable amplitude sinusoidal signal to a square 5V signal to match the PCB from injection engines.

Why didn't they use the ECU of diesel engine in a similar way to injection engine?... beats me. Bottom line is on diesel cars that have a tachometer fitted from factory, an additional HCF4040B IC (integrated circuit) is used to convert the signal from sinusoidal to constant 5V square and halve its frequency.

But don't lose hope. There's good news too. The first good news is that many PCBs from 1.3 SPI or MPI cars have all the necessary copper pads and traces to add this extra IC. So no messy wires, no ugly soldering. The second good news is that the extra IC is very common, easy to find and very cheap.

Let me know if you find the solution too hard to implement or if I should go on with details.