digging up an old thread but I thought some folks might like to know that the diode is not needed to display miles in the odometer. I didn't have access to a diode locally so I decided to try just swapping the resistor and it worked. the only issue I am having right now is the temp gauge is pegging hot but this could be unrelated to the conversion. hopefully you can see the missing diode in the second picture.

 

Just did this on my 92 jdm cluster. Moved the resistor to the right, odometer lit up in miles and converted the km’s clocked to miles. Adjusted the potentiometer with a gps app. Worked perfect

 

amazing

 

 

Hi Dale. I found your thread as I,m having some probles with my clusters… first my original speedo stop working and then a weeks later the odometer did the same , it has about a 41.478 miles but the first "4" for the "thousand" just shows the middle trace, like -4.478 Miles.
I've bought a second used one from KnightSports that a few months later that stop working also, this time just the odometer that went blank… unfortunatelly here in Portugal there are no "Wankel Culture" or shops where I can go to… I spent thousands rebuilding My FD as I bought it as a scrap and had to import most of the parts, rebuild the engine myself… for now I,m just having some few issues but the electrical ones are killing me...
Is it possible to remove the speedo needle to use the graduation speed mask to fit in a JDM cluster and them calibrate the speedo?
here in Europe we use kms instead of miles… using your explaination from kms to miles must I do it in reverse?
Thanks.
Best regards

Nuno

 

Nuno,

To answer your question, you can convert a KPH speedo to MPH and an MPH speedo to KPH by moving the resistors to the locations that Dale previously discussed. Is your FD a manual transmission? If you wish to convert an MPH speedo to a KPH speedo then you would need to move the SMD resistor from the R15 position to the R14 position.

Once that is done you could solder on a KPH speedometer face and then follow Dale's recalibration procedures. The calibration procedures are in another thread.

Additionally, you could attempt to repair both speedometer boards. There are a few threads that discuss it. I haven't seen a negative value on an odometer yet. You can read turbo blue's thread here: just got done figuring out how to fix an FD odometer and my thread here: Troubleshooting the FD Speedometer-Odometer-Tachometer Circuit Board

Post to the "Troubleshooting the FD Speedometer..." thread if you want help in diagnosing the problem with your specific boards. It sounds like the capacitors on both boards have caused some damage. The question that remains - how much damage did those capacitors cause?

As a precaution, be careful not to overheat the solder contacts of R14 through R17 with a standard soldering iron. These pads are easily damaged when using a standard soldering iron. These resistors are SMD (surface mounted devices) and require a different type of soldering iron. Will a standard soldering iron work? Yes, but the results may not look pretty. Moreover, the risk of damage to the board's pads and solder runs significantly increases with multiple heat cycles from a standard soldering iron.

Did I answer your question?

 

Gen2n3, thanks for your time... I've already replaced the electrolitic condensers but the problem remains.
I've also soldered the kph speedo into the mph circuit board with the intention to convert the mph to kph but now this speedo it's malfunctioning too, the needle raised quickly as it was badly calibrated and then stop at 190 kph and staid there. I've contacted the Circuit Board Medics and they told me that don't repair my Instruments, for being the '92 version, if it were the' 93 and ahead they would repair, but not the '92 one.
Do you know if someone has a cluster instruments in good condition for sale, although I'm a bit sceptic about buying another one and it fail as it happened with the KnightSports one?
Thanks

Nuno Gomes

 

@RX7 tuga,

Just because you replaced the capacitors does not mean the board will be fixed. It may take several repairs to get the speedo working properly.

Did you make the repairs yourself or did you have help replacing the electronic components? How much experience do you have with electronic troubleshooting? If you would like, I could offer more advice on its repair. However, you would need to remove the speedo and post photos.

If you are looking for a replacement then you could post a WTB ad in our classified section. You would be getting a used unit, unless you contact Ray Crowe, or other RX7 parts guru.

I recommend that you verify the wiring going to the instrument cluster. Do you have access to the BEM (Body electrical troubleshooting manual) and WDM (wiring diagram manual)? Refer to Diagram C-1a in the WDM to verify the wires going to and from the instrument cluster. Then once you verify the wiring in the car is good then move to the instrument cluster and speedometer board.

I provided 2 links in Post #56 as a resource for you to use. When you are ready to tackle the speedo board, then make a post in the "Troubleshooting the FD Speedo..." thread. I'll be happy to lend a hand after I can review photos of your speedo board.

Does that help?

 

For the guys asking about the different code of the chip, i made the swap and every things are working well.

I swapped the chip even if the code were different and is working well ;-)

For conversione from miles to km i just swapped the R15 (472 smd) non need to make other change with zender diode.

Again Thanks Dale for tips

 

Has anyone figured out the configuration to change the JDM 180kph scale to read the 280kph/180mph scale and keep the odometer reading in km's ? Canadian speedo's had the 280kph outer scale /180mph inner scale and odometers reading in km's. thanks

 

Should just need to turn the calibration screw to get it right, it's no different. Just adjust until it matches a GPS speed app on your phone.

Dale

 

Ok thanks...I didn't know/realize there was that much authority on that pot adjustment...that should be easier then desoldering and shifting smd resistors.cheers

 

Hello everyone. I live in Poland and here there is no one to help me in the subject of rx7. I have a counter like in the picture. According to the guide, I changed the position of r15 to r14 so that it showed me km and not miles. It works ok.


I have a question if the r16 / r17 position should also be changed so that the clock shows km/h in small numbers or will it show km/h in large numbers? From my logical thinking, I could leave the r16 / r17 position and the odometer will show in miles and I will read the small digits how many km / h. Will there be no distortions? Is it better to change the r16/r17 position and set it with GPS? This might be a stupid question but it's really bothering me.
I will add that now I have left the r16 / r17 position in the mile position. According to the GPS I have 15km/h and the odometer pointer doesn't even move. Only when I get to 20km/h the odometer pointer jumps to a small number of 20km/h quite quickly. this is annoying because it does not read lower speeds
Thank you for your help

 

This is the question I had above. By the sounds of it changing r15 to r14 gives you km's instead of miles on the ODO and changing r16/r17 changes the scale of the speedo from 180mph (280kph) to the 180kph needle scale. Can anyone else confirm that?