Ok, my speedo and tach either both work, or both don't work. I have searched and found out that the tach gets all the signals and what not from the speedo, but others have seemed to have a working tach, and not a working speedo so i am not sure what to check.

I've checked these links which are all "fixes" of some sort, but no one has really said that they both either work, and both don't.
http://www.umsl.edu/~tch9gd/Tach.pdf
https://www.rx7club.com/showthread.p...z+turbo+timerf
https://www.rx7club.com/showthread.p...hometer+solder
https://www.rx7club.com/showthread.p...highlight=tach
https://www.rx7club.com/showthread.p...peedometer+fix


When i drive my car they usually are both off, then sometimes as i'm driving they just both start working. It is never just one or the other though. Right before this started happening my odometer would start flashing too (still does this) it won't ever stay on for a long time, but it still flashes on and off every now and then.

Would it be my speed sensor, broken solder points in the tach, broken solder points in the speedo, any one have any idea at all? i recently cleaned the connections into the dash in hopes of fixing this, but it didn't do anything. The rest of the gauges work fine (oil, fuel, water temp)

Thanks,
Harrison

 

Check the plug coming from the engine wiring harness to the dash harness. It will be the first connector you run into when you trace the harness from the grommet in the firewall back to the ECU.

 

thats the white plug that branches off right before the harness gets tucked behind the metal plate correct?

 

Yes

 

This is working so far, but i've got to drive it for a few days to make sure it doesn't act up again. i'll try and update this in a bit. ( it did seem however that this connector might have been subject to some moisture, as one of the screws on the blower motor seem a bit rusty. Water could have gotten into the connector and messed with the contacts)

 

ok, not a fix, it might still have something to do with this, but it will still turn on/off by itself. Do you know what wire going into that harness is the power? i want to check it before and after the connection and maybe try a jump.

 

bump, from what i'm seeing, i'm guessing it is some kind of power issue, (being that they both shut off at the same time) I'm pretty sure my CPU#2 is kinda F*ed up because my seatbelt light stays on constantly. The wiring diagrams shows a wire from the Speedo going to CPU#2, could this possibly be the cause?

 

ok reviving this thread,

i have the same issue except when mine occasionally work they both seem to be reading low or high (usually speedo reads high tach reads low). i also have a power fc and when i set it up to display speed on the monitor setting it always says 0km/h does this sound like something to do with my speed transducer(thats what my mech called it)

Brad.

 

Brad,
have you done any work on the instrument cluster? did you remove the gauge hood for any reason? If so, check the flex print connectors - rub the contacts of the flex print with an eraser then wipe off with rubbing/isopropyl alcohol. Afterwards, bend the flex print in towards the center. This will ensure the flex print makes good contact with the hard plastic connectors that plug into the gauge cluster.

 

no i havent done any work to the cluster, i did however have it propped up and out of the way to remove some old gauges and i did have the harness out of the car during the rebuild to remove unnecessary components from it. the tach is about 3-4 hundred rpm low and i believe the speedo is a little high and sometimes these two dont work at all. but the main thing that i cant quite figure out is that the power fc reads 0 all the time. i gotta get under the car and take some pics of the plugs on the gearbox and post them up for all to see whats going on.

ps please explain what the flex print connectors are.

Brad.

 

also i have the opportunity to get a knightsports 300km/h cluster (ie complete cluster with 300k speedo fitted) for quite cheap but is there anypoint if its not going to fix anything?

 

Brad,

Flex print is a paper thin plasticized material with flat and flexiable solder runs. If you open the backside of your computer keyboard, you will see it.

Take a look at this thread to see the flex print on the gauge cluster (10th and 11th pics). It is in blue. In the 11th picture, you can see a few rectangular cutouts. That is where the connections are made.

https://www.rx7club.com/showthread.p...=gauge+cluster

Hope this explains further. Have you found the problem yet?

George

 

nah mate i havent had a chance to work on the fd i've been too busy enjoying driving it. i read on this post: https://www.rx7club.com/showpost.php...4&postcount=10 that the tach runs directly off the speedo. i've bought a new cluster (complete with 300kmh knightsports speedo) to put in and i will be checking the connectors on the gear box to see if theyre all plugged in where theyre supposed to be and i will try to check the speedo transducer to see if its faulty or whatnot. hopefully this will sort out my cluster issues

Brad.

 

have you installed the new gauge cluster? Did it fix your problems?

Adam

 

I know this is an old post but I am having the same problems... One day the Odometer quit showing mileage, the very next day the Tach and Speedo quit working simultaneously. Every once and a while they will both work. Mine is like yours either they both work or neither work. Also now have an annoying continuous buzzing sound like I am low on coolant when the gauges aren't working. The buzzing also goes away when the gauges come online.

 

Replace these http://www.soothingpain.com/diy/8.jpg 1uF 50V condensators and resolder everytihing you can. I recomend replacing all of those in the same time.

 

My tach stopped working. The circuit board attached to the speedo was the culprit, as tach signal comes from this board.

 

if anyone here replaced their old non working unit please let me know. i am looking for non working clusters. i only need the flex print on the back as i screwed mine up doing some mods to it so please let me know asap as i would like to have gauges again soon.

 

thanks to anyone in advance

 

I replaced all the capacitors and it still didn't work. Resoldered everthing on the board and now she is alive and well again... At least for now.

 

Ok bringing this back. I still can't get mine to work. Anyone, since Chad hasn't been on, know what he all connected to? I see the top wires but not sure what they are connected to. Are they both power since I see the grounded alligator clip on the bottom that I assume is to the negative. I see the green wire has one end to ground but not sure what the other end is connected to.

 

Lots of threads on different things to check. Have you read them all yet?

 

I know there are a ton of them I'm pretty sure I have read them all. Knowing my luck I probably missed the one I need. Going to try a few more things before I just pull the entire board apart and redo it all

 

I recently had just my tach stop working. I sent my cluster to Dna speedometers in Florida to get it fixed and they sent it back to me not working. I sent it back to them again and they sent me a video of the tach needle moving while wired externally. They sent the cluster back to me for a second time with a tag that says under warranty but it still does not work. I'm trying to sell my car and cannot finish it until this is done. What a pita!!!!!!! Any help would be greatly appreciated.