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I fixed those issues, the gauges all now work, things are no longer turning red hot and burning plastic, but I still seem to have another issue that I cannot figure out.
When the key is on, I am getting a constant light buzz from that buzzer that rings when you hit RPM, Low oil, or low water level. If I go to those sensors, and ground them to the chassis, the buzzer gets proper loud, which you would expect. The charge light on the center warning cluster is lit up, I found that the original alternator was bad, replaced that, and the new alternator is outputting 14 volts, so that is fixed, but the light is still lit. Unplugging the plug on the alternator makes no change, so am leaning toward something with it being bad, but not sure where it goes to to check. (see picture 1)
As per my last thread, my car did not have any ground that attached to the clutch cylinder, so am not sure if this is part of this problem. I have not been able to find any pictures of where this ground is connected to, as my clutch master has the bolts go into the cabin and the nuts are inside, so I dont see where it could even bolt to? (see picture 2)
Alternator plug Ground on clutch master? Is it that plug in the lower left? Yellow or an faded old white with blue stripe?
I would suspect that something is wrong or burned out with your center cluster, or that the 14V that you measure at the alternator is dropping considerably by the time you get to the cabin (through old and worn relays, the ignition switch, etc). An easy way to check the voltage is to measure the difference between the dot at the bottom of the cigarette lighter and the metal around the outside of the cig lighter. This should be close to the same as the battery when the car is on and running, as well as when the ignition is on but the car is off. If this is OK, then pull the cluster and check the same thing - it has unswitched and switched battery voltage fed to it, and sometimes if there's enough of a difference between them (such as due to a large V drop across the ignition switch or main relay, etc), this can cause some strange issues like the buzzer slightly going off, charging light or other lights staying on, etc.
Adding grounds between the engine block (where the battery main ground goes to) and the body (especially at locations where the wiring harnesses already ground, such as under the coils near the brake MC, at the firewall etc) can only help, so I'd suggest adding those regardless.
I do have another dash cluster coming in sometime this week, will test it with that. Was going to use it to replaces the burned gauge faces, but will see if it is still doing the buzzing too
the capacitor thing is on the clutch slave, not the master. or it can be near the slave. also make sure that the wire to it is ok, and not touching the engine/trans
When I pull the oil level sensor and ground it, the buzzer gets noticeably louder
When I pull the radiator water level sensor and ground it, nothing happens
When I hit redline, where the buzzer would normally go off, it stops.
I have a feeling the issue is with the water level sensor wire. I have to pull the dashboard again anyway to do some stuff with the HVAC fan, so looks like I will be rerunning that wire, as I think it is acting like a floating ground or something and shorting somewhere when you get to redline
I do not have a capaciter on the Clutch slave, but there is a wire grounded to the transmission bellhousing behind and more toward the passeneger side, am not sure if that is the same thing just moved, or a different wire. I cannot find anything else that would terminate in that area.
I have taken the dash cluster apart again, and gone over the circuit board with a Dremel w/ brass wire brush, just cleaning any residue from the solder joints to make sure that nothing is shorting.
I also realized that I have an aluminum radiator, so I grounded it to the chassis so the water level sensor can send its signal.
Result: Buzzer is still weakly buzzing. New behavior is that when I unplug the water level sensor, about 10 second later the buzzing gets louder, when I plug it back in, it goes quieter. If I unplug the water level sensor, jam a wire into its plug, let it get louder, and then ground that to chassis, it goes quieter. Remove the wire, and 10 second later it gets louder again. This change in volume was not happening before when I unplugged the water level sensor. The sensor is brand new. Maybe the grounding of the radiator to the chassis did this? it was isolated with all the rubber before, but the old radiator was also a lot of plastic. is it maybe that I need to isolate the radiator more?
A reminder that when I grounded out the oil level sensor wire to the chassis, it does the same thing, except no 10 second delay
The brown /w blue wire that goes into the dash cluster, which haynes manual says is the water level sensor, if I unplug it, there is no change to the buzzer volume. In fact the entire black plug being removed has no effect, am currently in the process to narrow down what on the white plug is sending enough power to weakly make the buzzer go off.
If anyone has any ideas, please let me know other things to try
As far as I can tell, there is nothing wrong between the water level sensor and the oil level sensor.
Given that the weak buzzing sound turns off when you get to redline, instead of getting loud as expected, is making me think that something is wrong with the tach itself, and it thinks that I am already as a redline condition and why it is weekly buzzing until I hit redline and then it turns off because grounded?.
Does anyone happen to have pictures of one taken apart that is known good, so I can compare to what I have?
So what I think I had happen. I had two RX7s, and one was a parts car that was broken with most engine stuff, but the interior was good. I had two clusters and when I first started fixing up this car earlier this year, I had taken them apart and took the best parts out of each. I think when I started to put everything together, I just filled every hole with a screw. What I found is there is a screw hole with the marking O-R near it that when I was unscrewing each one-by-one, it stopped the buzzing, and all the gauges continued to work. In this picture it is the screw in the upper left that is unscrewed a bit, so it does not make contact with the circuit board.
The water level and oil level are still functional as well. I will need to test later if the RPM buzzer is still working, but the two important ones are working, so not super worried about the RPM one.
Can anyone else confirm on a series 4, if this screw is present on theirs or if it is purposely omitted?
This thread doesn't apply to any issues I'm currently experiencing, but I just wanted to commend you on your full walkthrough and posting of the solution. I'm sure many will appreciate your efforts. Thanks for the quality post and follow-up.
One final update. That O/R screw does seem to be the one connected to the tach buzzer.
I dont know what is causing mine to lightly buzz all the time, and then shut off when you hit redline, but mine is now silent, so if anything, this is the part to remove if you dont want it buzzing with shifts.
there might be some other grounding issue with my tach itself.
My water level and oil level sensors still operate as expected.
