TeamSwift

The following applies ONLY to ’98 up Metro/Swift tachs.

I found a ’98 Metro 4cyl automatic instrument cluster at the local wreckers for a good price. My buddy has wanted a factory tach for a long time for is ’98 3cyl 5 speed, so I purchased it.

I posted a request for info to recalibrate the ’98 4cyl distributorless tach so it would function on our 3cyl that uses a distributor. I found no posts that deal specifically with the later model ’98 up tachs and had no replies. The photos I found in older posts are of earlier model tach circuitboards that do not match the ’98 up boards.

Since I have a 2000 3cyl 5 speed Metro I decided to remove the tach and compare the 4cyl distributorless to the 3cyl tach with disty. What follows are the results of my investigation.

It is possible to reverse what I've done and recalibrate a 3cyl disty tach to work with a 4cyl distributorless engine by using the proper component values.

The tach boards themselves are identical, but have some different component values. All that has to be done to remove the circuitboard is to bend the four tabs holding it onto the meter movement and pull the board straight out. Four pins fit into fours sockets on the meter. I used a black ink pen to make registration marks so I wouldn’t be tempted to re-install the board backwards.



Next is a pic of the board with reference designators for the components. The chip is proprietary. The nearest chip on the market that probably functions the same as the Denso chip can be found here.
http://www.datasheetcatalog.org/datasheet2/2/04esl39ylzhhqglqedzptpxc9oky.pdf

Look at this data sheet for a similar chip to read an interesting explanation as to how Air Core Meter Movements work.
http://www.datasheetcatalog.org/datasheet/nationalsemiconductor/DS005263.PDF



I replaced the OEM resistor network R6, R7, R8 with a single resistor in series with a 10 turn pot. I used an old computer audio cable to connect the pot to the board so that it can be accessed from the front of the instrument cluster when the cluster is installed. You can easily make fine calibration adjustments to the tach using the pot. It nestles down into the recess of the cluster’s clear bezel and will be covered by the black instrument panel bezel. The pot can be tacked into place with a drop of RTV silicone if you think it’s necessary.



Following is a list of component values for both 3cyl and 4cyl versions of the ’98 up tach.

4cyl component values:

R1 = 390 ohm 1 watt (same for 3cyl)
R2 = 68K 1/4 watt
R3 = 91 ohm 1/8 watt (same for 3cyl)
R4 = 91 ohm 1/8 watt (same for 3cyl)
R5 = 24K 1/4 watt
R6 = 14K 1/8 watt
R7 = 5K precision 10 or 20 turn pot
C1 = 10uF 25v radial lead (same for 3cyl)
C2 = 10uF 25v radial lead (same for 3cyl)
C3 = .015uF 50v Mylar
C4 = 4700pf Ceramic or Mylar



3cyl component values:

R1 = 390 ohm 1 watt (same for 3cyl)
R2 = 33K 1/4 watt
R3 = 91 ohm 1/8 watt (same for 3cyl)
R4 = 91 ohm 1/8 watt (same for 3cyl)
R5 = 43K 1/4 watt
R6 = 12K 1/8 watt
R7 = 5K precision 10 or 20 turn pot

C1 = 10uF 25v radial lead (same for 3cyl)
C2 = 10uF 25v radial lead (same for 3cyl)
C3 = .022uF 50v Mylar
C4 = .047uF Ceramic
C5 = 2.2uF 50v radial lead (not installed on 4cyl)


All replacement resistors should be precision metal film, either 1% or 2% tolerance
C3 and C4 should be precision tolerance with low temperature coefficients (factory designations are ‘j’ or ‘k’)

I’ll post a pic of the schematic diagram of the circuitboard with details elsewhere in this thread. I’m afraid that the pictures are going to be too large to download quickly for some users. I can’t compress the schematic any further without making it impossible to read.

The recalibrated tach was tested and works really great. The pot allows for about +/-300 rpm adjustment. It's not overly sensitive.

Here's the schematic diagram.



Here's a link to a nice place to help you figure out resistor color codes http://samengstrom.com/nxl/3660/4_band_resistor_color_code_page.en.html

And this site will help with identifiying capacitors http://www.csgnetwork.com/capcodeinfo.html

As near as I can tell from all the cars I've had apart, and from GM's FSM schematic diagrams for '98 up cars, all of the wiring necessary to make the tach function in a non-tach car is already in place. The automatic transmission instrument cluster has the vehicle speed sensor (VSS) in the cluster so that manual transmission cars can use auto trans clusters.

Good luck. And if I've screwed something up in this post please let me know.

Beautiful, just beautiful.

_________________
'93 1.3 Swift GLX
'98 2.0 Grand Vitara

has anyone built one of these? i got of ebay a 1.o 3 cylinder 5 speed cluster with tach. i want to place tis into a 00 1.3 auto car. has this been done yet? it sounds in the post that the auto trans car has the necessary items already int he cluster. i don't see it but i may be there hiding someplace. or how much will one of you charge me if i send the circuit board to you to make the changes? thanks bob p.

00 1.3 auto
91 1.0 5sp vert
90 1.0 auto hatchback

Sorry I haven't got back to you but somehow I wasn't notified that there was a new reply on this topic.

Your cluster has to be from a '98 up car. Manual-to-auto or auto-to-manual should make no difference. Some clusters will have panel lights either installed or not installed, depending upon options such as ABS. An auto trans car won't have the upshift bulb so if your cluster is from an auto trans you'll have to score a holder and a bulb to make the upshift indicator function on a manual trans.

As I indicated in the post, the only difference that I could find - and I did my best to investigate thoroughly - is that the circuit board has different resistors and capacitors for 4cyl distributorless vs. 3cyl w/ distributor. I changed a 4cyl auto cluster to a 3cyl manual. You can take a 3cyl manual and change the components to the values that I found on the 4cyl board and they will work fine, I'm sure. The only rub is that the factory calibrates the tach on the bench. They jocky the values of the two resistors that are in parallel to do the calibration. So I suggest that these resistors be replaced by a pot in series with a resistor and that the pot be mounted as I've shown in the pic, which allows you to calibrate the tach using an OBDII scanner or other instrumentation after the cluster is installed.

Well, I thought maybe I would have someone ask me if I would do the job for them. It just doesn't seem like a good idea to try unless I have the car in front of me so I could do the whole thing at once, calibration and all.

Really, the job is simple. Anyone without the skills to de-solder the components and install the right values should be able to find a friend who can help.

The chip itself is identical. It's just a few resistors and two caps that need to be changed.

The board should be washed well with alcohol and dried with canned air after the soldering. The components can be found on Digikey's website. Radio Shack is probably not going to have the right parts. A local Fry's electronics failed to stock the values necessary. So I suggest Digikey or a local electronics supplier that has 1% or 2% metal film resistors of the right value, and mylar caps with the proper lead spacing. The caps should be mylar (polyester) and of the highest quality you can get. Cheap ones will have a loose temperature coefficient that could make the tach read different as the temperture changes. This may be a moot point for most people, but in terms of simply doing your best to make the tach work as well as the factory intended, I say try to find quality components.

Anyone who might find a different board layout from a '98 up car that's different than the one in my pics should attach a pic of it and let me know. To my knowledge there is no way that you can go wrong doing this modifcation.

Good Luck!

And have faith. It will work either way - 4cyl to 3cyl or 3cyl to 4. Or manual to auto or vice versa.

By the way, if you need Corvair parts you can PM me. I've got a buddy who's up to his ears in Corvairs - mostly later model though.

well i will have to send a photo to the site for you to see. my circuit board has a jumper wire i=on the board that is not shown in the photo you have here. the tach i have now i swapped to a guy on the Geo metro site. he has a 3 cylinder 5 speed and had this tach from a 4 cylinder. but he could not remember what year it came from or what distributor trans it had. can you tell from a picture of the component side what the board is for and if i can just make the changes you say and it should work? thanks bob p.

notice the jumper wire to the left of the chip it jumpers pin 6 and 7 . but in the instructions this jumper is not present? can someone tell me if i just remove this will it work for a 2000 1.3 auto system?

I'm certain that the board in your photo is from a '97 or earlier 3 or 4 cyl. Note the diode just below the light blue power resistor in the right top corner. The later '98 up board does not have this diode, or the jumpers you refer to.

If you search the forum you will find matching pics of your board in the posts for modifying earlier tachs. Even if you have a '98 3cyl the signal will be the same and it will work. The board in your picture will not work with a '98 up distributorless 4cyl, though.

If you want to use this tach on any 3cyl it should not be a problem. Follow the instructions in the earlier posts for calibrating it using the two parallel resistors and I will bet anything that you will be successful.

The difference in the '98 up boards were necessary for dealing with the fact that the 4cyl is distributorless, and the 3cyl still has a disty. In pre-'98 models the 4cyls had distributors and the signal from them was very similar to the 3cyl signal, except for an extra pulse.

I'm sure you'll find that your board is an early model. So follow the forum instructions for modifying an early model tach.

Get back to me if you have questions or problems.

Sorry I might have mis-read your post. It sounds like you want to use this tach on a 4cyl. If it worked on a 4cyl, no problem - as long as you don't put it onto a distributorless 4cyl. This board was intended to work WITH a distributor.

I now wish I'd taken photos of the trace-side of the board when I had it apart . . .

Or you could flip your board over and trace everything out according to the schematic diagram. If you can mount the right components on your board and have them connected according to that schematic, you could have what you need for a distributorless engine.

The diode could have been included merely for protection against reverse polarity on the power. The jumper is an unknown. We don't know if your board has the same chip as the new later model boards that I used to make this post . . .

Sorry I'm so scattered in my thinking tonight. It's been a long day.

thanks. it sounds like your saying this bd. will not work and i can't make it work correct? if this is so aside from just shooting crap at a junk yard , does anyone know where i can locate a 4 cyl. 99 and up tach that i can install in my car? i have this one i can even trade someone. thanks bp.

Sorry I was so tired when I posted last night.

What I intended you to hear was that you could trace the connections of the circuit board that you have and compare that to the schematic in my post. That would tell you if you could use it or not on your distributorless 4cyl.

When I look at the pic that you posted of your board it seems that the holes may be the same and so maybe the traces are, too.

Just take the time to trace the connections and compare to my skizmat. You might able to put the right components in and see if it would work. It seems doubtful that they would change the chip, but I guess it's possible.

But anyway, it's worth the time it would take to trace things out and compare . . . don't give up so easily.

i have checked that already and they are the same. the difference is the solid jumper from pin 6 to pin 7 and a cap is milling from the bd at c5 for the 3 cyl. plus i have the diode under the r1 if you like i can take a picture of the trace and post it here or send it to you directly. just for a test i cut the jumper at 6 % 7 terminal on the chip but no difference. thanks bp.

OK. If the board you have makes the same connections as the schematic diagram using the traces on the back of the board, just desolder the jumper, the C5 cap, and the diode. Put all of the components in that I specified for making it a 4cyl board (listed in the post).

But I'm not sure your jumper actually connects pin 6 & 7. It looks like the jumper is adjacent to pins 5 and 8, which would make more sense when you look at the schematic. Pin 6 should be connected to a ceramic cap.

If you haven't done so already, maybe you could turn the board over so you can see the traces and then draw out all of the connections that the traces make. Then compare to my schematic.

If your jumper actually connects pins 6 & 7 of the chip, you may have a different chip.

Check exactly which pins are connected to that jumper by looking at the traces.

Pin #1 on the chip is the upper left pin in your pic. They go down the left side to pin 8, and then up the right side to the upper right which is pin 16.

Let me know what you find and we can work this out. I'll keep and eye on the post.

ok here is the circuit bd for all to see what im referring to. my bd looks the same but for the diode the missing c5 and the jumper from pin 6,7 on the chip. i tested it with the jumper cut, and i have not yet reconnected it.

the chip number is d056956-0140
9533kb

the last 2 pictures are copied from above to be used for reference. if you look at the rear picture of tach bd you will see on the rh side 4th down a pin with n/c the next pin is 5 and the next is 6 this is where the jumper is located. that pin and pin 7 have the jumper connected. pin 2 is connected to the signal by a resister pin 3 has a cap on it. pin 4 n/c pin 5 has a cap and both pin 3 and 5 go to ground on one side. pin 6 has a cap a resister and that jumper. plus the resisters that go to ground. pin 7 is the other side of the jumper and an empty spot that the c5 cap for the 3cyl goes to. pin 9 goes to a resister and ground. pin 10 goes to the meter. pin 11 to the meter. pin 12 to the meter and 13 to the meter. pin 14 to a resestor. pin 15 to a cap and to pin 1 then to that big resister and that big diode. pin 16 goes to a resister and to pin 15.

that is the pin out. it looks to me the same as the print in this picture copied from above. hope this helps. if it helps i can send the board to you for more detail. i don't want to take stuff off until i have more information. the book for the 2000 shows the tach input to the tach but it fails to show any info on the tach bd. or what type if input it is but it show the pcm in a dotted box with a variable resister in it, may be a calibrating pot. but i won't mess with that until i get the tach itself to work. thanks for the help.

Your pics are way to small to show sufficient detail. Even if they were larger it would be difficult for anyone to trace your circuit. You have the board in hand. You can easily trace out the circuit and draw it on paper, pin for pin. Then compare it to the schematic in the original post.

Just cutting the jumper means nothing. Look at the value for R5 as an example. For the 3cyl it is 43K. For the 4cyl w/o disty it is almost half as much - 24K. The current for the 'signal in' flows through this resistor. This one component alone could prevent the circuit from working on a 4cyl distributorless engine - the chip would not receive a trigger signal.

The other components determine the calibration and accuracy of the tach.

Have you done what I suggested? Remove the diode, jumper, and C5 cap and install the proper component values for your 4cyl w/o distributor? The values you need are listed in red text above the schematic diagram.

Obviously the placement of the components is the same on your board and the one in my OP. Replace your components with the proper values and remove C5, the jumpers, and the diode. It's worth a try.

I'm still skeptical that the jumper connects pins 6 & 7. If it did, and you had C5 installed as well, then C5 and C2 would be paralleled which would be senseless.

I suppose I set myself up for this sort of confusion by not posting pics of both sides of the late model circuitboard. But I assumed that anyone who would make this modification would take it seriously enough to simply trace out their circuit if there was any doubt as to whether their board was '98 up or not . . .

OK. I have to apologize big time.

I'm working on a small laptop screen and did not see your text detailing the connections on your board. I am so sorry that I missed that.

Yes, your circuit matches perfectly.

Go ahead and change the component values and you are good to go. No problem.

The problem here is on my end of the discussion. I need to pay closer attention and work with a bigger screen . . .

ok thanks. i see you posted the place i can order them from. i will go there and place an order for the components listed for the 4 cyl. and install them. i will test it and post the results when i can. again thanks for the help. bob p.

And I apologize again for my lapse of attention to your post.

Good luck finding the parts, and I know that the mods will work fine for you. I've done several and they work really good with that pot in there to fine tune the calibration.

By the way, the wiring diagrams in the factory service manual typically use a symbol like a resistor to denote an assembly like a circuit board or a sensor. That doesn't mean that a resistor is present in the vehicle, just that the ECU (or PCM) 'sees' a variable resistor in place of the component or sensor that they don't show in detail.

Let me know if you need any of the circuit diagrams for the 2000 metro. I have an online (DVD) version of the manual and the electrical diagrams can be sent as gif files attached to an email. If I search the database with a VIN # I'm certain to get the exact diagram for that car. They are very clear and concise.

thanks wired. say i looked back in this topic and i didn't see the reference to the place i can get the parts i need. i do recall some mention of radio shack not being a good place to get these. the links in this topic are for information on the resistors and the caps. do you have the link for the site i can get all the components i need? thanks bob p.

If you have no local electronics supplier use http://www.digikey.com/

I have parts from a 4cyl board that just got shoved aside after I set it up for a 3cyl engine. They're in perfect condition. I use a professional desoldering tool to remove components, so they come out clean and undamaged.

If you'd like to PM me with a PO box or physical address I can mail them tomorrow (Monday 20th April).

I don't have a 14K resistor since the only mods I've done have been 4cyl-to-3cyl. But I can send a 12K and you can substitute a 10K pot. This would give you a bit more range for adjustment and probably not hurt anything else

The pots like the one in my pic of the finished installation are a standard radio shack item.

Maybe you could take a look at the resistors on your board and see if the colors look the same as the ones in my closeup pic of the unmodified 4cyl board. Note that some of the resistors are the same on both 4cyl and 3cyl boards. A quick check might be a good idea to find out if there might be other values that you'd need besides the ones I would send.

You might be able to get up and running a bit sooner with my old 4cyl parts, rather than wait on a digikey order.

well thanks. that may help and i will stop to a radio shack in my town for that pot. my address is bob palmer 1393 quarterline rd. muskegon mi. 49442 as far as i can tell the values on my bd are the same. i will replace those parts and see what happens.
bob p.

So are you saying that your board already has the same values as needed for 4cyl distributorless function? That would mean that R5 would be 24K - Red, Yellow, Orange. And C3 would say '153' with a 'j' or other letter as a suffix? And C4 would say '472' with maybe a 'k' suffix? Then R2 would be Blue, Gray, Black, Red, Red - 68K?

If your board has those values it is a 4cyl board. The only question is whether it is a distributorless 4cyl, or for use WITH a disty. R5 is going to dictate that. It allows the smaller signal of the distributorless system to trigger the chip. With a distributor the trigger signal is a higher voltage pulse and needs the higher resistance to lower the signal to the chip.

If you already have the above components on the board and it does not work, then something else is wrong, like the tach isn't getting a pulse or the meter itself is not working.

Or, we could have a different chip on the board. But I really doubt that.

Get back to me and let me know what values you've got on that board. if your pic was larger I could see the colors, but I can't. From what I can see it doesn't appear that R5 is 24K.

I'll get the parts out in an envelope to you regardless of whether you need them or not.

ok wired here is more close up pictures if they are not to big if they don't go thru i can send them directly to you. my email is [email protected] the cut connections are when i installed a pot in the circuit to test. i have not reconnect it. you can see close up the jumper wire i cut for a test also. here are some as close as i can get for you. i include a Shadow photo of the circuit traces for you to see for yourself where all the components are on this bd. thanks very much. bob p.

My input on this tacho IC is that this unit is just a frequency to voltage converter there was a formula in one of the IC specs that showed
frequency and calibration resistor values are directly related, reduce pulse input for 4x per revolution to 3 x per revolution is 1/4 to 1/3
or 25% to 33.3% increase of aprox 8%

Full scale is 8000RPM as picture showed.
At 8000RPM x 4 pulses/revolution /2 for crank to cam = 16000 pulses/Min or 266.66 pulses/second or Hz
at 8000 RPM x 3 pulses/revolution /2 for crank to cam = 12000 pulses/Min or 200 pulses /second or Hz

To calibrate for 4 cylinder car use a frequency gen at 266.66Hz at pulse input to achieve full scale 8000RPM
for 3 cylinder car use a frequency gen at 200Hz to achieve full scale 8000RPM

Those resistors can be adjusted accordingly basically increase the resistor value by 8% for 3 cylinder motor as less pulses per rev.
you should adjust for full scale defection 8000 RPM to get most accuracy.

Hope this helps you calculate the resistor value.
I would use the fixed resistors if possible as trimpots change with temp and humidity.

the problem I'm having is not calibration but the tach just is not responding at all. the tach worked in another fellas car but he had a distributor in his car, and his car was a 3 cyl. I'm trying to get this tach to work in my distributor less 4 cyl automatic car. thanks. i don't car if it is right on the money for the engine. if it is 500 rpm's off that is fine. i just need it to respond to the engine. but thanks for the input. that may help others watching this and trying to get there tach's to the exact rpm.