Hello everyone, I'm bringing my FD back from the dead after a few years of storage. Got things going in the engine bay, but on the instrument cluster the LCD display and tachometer are dead. They are backlit but no number and no needle movement. Oil pressure gauge does rise. These were fully functional when the car was last run.

I've stared at the wiring diagram for a common connection but I haven't seen one yet.

I've already unplugged and plugged in the C1-01 connectors from the back of the cluster to no effect. Looking for suggestions where to start - in the cluster itself or maybe the wiring?

One other question - it's been a long time - do I need to pull the steering wheel to get the hood / cluster out of the car?

Thanks,

David

 

Does the fuel needle move also? And coolant temp? If so i'd suspect some leaking electrical components on the board over the time it was in storage. You can remove the cluster without removing the wheel if careful. There is a person in Canada with a great reputation on fixing these now, I suspect they will chime in.

Here's a thread with the removal process: https://www.rx7club.com/3rd-generati...emoval-803933/

 

No, the fuel needle and coolant temp do not move. I have the hood out now, I did it with the wheel and A pillar gauges still in place. There's very little room but it's possible.

I'm going to check for 12v+ on the power wires now. 2D, 3E, 3F, 4E, and 4C on C1-01.

David

 

If I'm interpreting the wiring diagram correctly, it looks like various parts of the gauge cluster get powered by the 15A Meter fuse and also the 10A Room fuse. It also looks like there is just one ground wire (Pin 1E on C1-01), which gets grounded via the engine harness near the intake manifold. If your engine harness is disconnected (blue X-17 connector near the firewall / passenger footwell) that might explain the cluster not working.

 

Hi Scotty thanks for dropping in.

1E shows continuity to ground.
2D shows 12v
3E shows 4.6V
3F shows 0.7V, or 0.0V at the instrument cluster (C1-01) and also the diagnostic box (#20, Y/L)
4E shows 12v
4C shows 5v

So far I'm suspicious of 3F. I assume it should be 5v. Especially how I can only sometimes get 0.7V.

 

3F should be within 0.3 to 0.8v per the FSM, as documented by pin 2B of the ECU.

So unless there are any other wiring items that 'feed' the instrument cluster, it sounds like I'm tearing into the cluster itself.

 

Found a burst 1000uF capacitor on the speedo board. It makes sense that it would cause the others to not function since the speedo board seems to drive the other gauges. Unfortunately I don't have any of that size in my stash so it will be a few days until I can confirm the solution.

 

Very interesting. By the way, Pin 3F is the tachometer signal pulse that the instrument cluster receives from the ECU (pin 2B ). It's OK for that to be 0V with the engine off. It's actually a pulsed signal when the engine runs, but the service manual probably assumes a tech will use a multimeter to check for DC voltage and not an oscilloscope to check the actual pulse waveform.

 

Most likely it's the cluster. The electronics are really starting to hit their age limit and cluster issues are becoming more and more common.

Michael Gagne in Canada (he's very active on the FB RX-7 group) does an excellent job repairing clusters. He has a whole test rig that he can totally test and calibrate everything.

There's a huge thread going on cluster repair but IMHO in some cases it's worth sending to someone who can test and calbrate it so you know it's 100%.

Also glad to see you back around the forum!

Dale

 

Welcome back - I've learned a lot from your archived info, and I was thinking that you had some disaster that caused you to be inactive on the forum.

 

see the thread:
Troubleshooting the FD Speedometer-Odometer-Tachometer Circuit Board
which also identifies other threads on the cluster circuit board problems.

many of the electrolytic capacitors can be leaking, and that leakage not only disables the capacitor function,
but can damage other components and contacts. Old flux on the board from poor manufacturing control can also flux things up.

Several of the shops that used to replace the capacitors and clean up the boards have quit working on them.
The capacitor component replacements are available; I just had most of them on the board swapped out.
I got lucky and found a local electronics techy with all the right equipment and experience to fix mine without creating bigger problems.

( however, my tach was still working....)
Good luck.

 

Well I had an inspection appointment this past Tuesday, and replacing the C3 with another 1000uF capacitor brought it back to life enough to get through inspection. That cap was pushed out but not leaking. But the tach was erratic and last night the odometer came and went - so I'm going to pull it and send the cluster out for a full refurbishment. I have the names Michael Gagnon in Canada and Geoff Pritchett in the US.

DaveW, you've been here at least as long as I have. I've learned a lot from you also.

Dale, long story short I spent about a year fussing with my instrument cluster and intermittent engine shutting off. Got that fixed with a "good" used cluster and took it to an autocross. 3rd run, my radiator sprang a leak and I had to trailer home. There it spent 4 years on jackstands as I puttered around doing other things and wasting inordinate amounts of time trying to procure radiator brackets. Yes, laziness kills cars. I had to pull the injectors for cleaning, drain the tank, change fuel filter, new FPD, etc.

My new problem aside from the failing cluster is driveability. I've been babying it since the fuel system overhaul, just 30 miles so far. The car has a base mapped PFC and at medium throttle (0 vac, 2.5k-4.k rpm) it sometimes bucks and cuts out. God knows how many wires and sensors I went by in the process of the injector job so I'm back to checking all of that stuff. Debating whether I should install a fuel pressure gauge and/or a wideband O2 sensor as diagnostics or peace of mind.

 

I would go with a wideband before a fuel pressure sensor/gauge, if you can only get one. I'm not familiar with the process of connecting to the PowerFC, but I've seen PowerFC people talk about datalogging the wideband AFR's so it should be possible.