3rd gen coolant temp gauge inop
 

Everything else seems to be working on the panel, except the odometer died several months back.

Any prime culprits or hints on checking the temp gauge wiring?

93 stock

The easiest thing to start with is looking at the single wire temp sensor under the oil pressure sender. That's the one for that sends signal to the cluster.

Take a look at the Body Electrical troubleshooting guide, pg C1-16 to test the water temp gauge in the instrument cluster.

While the instrument cluster is out of the car, take a look at your speedometer board for your dead odometer.

See these two links to help with the blank odometer:
https://www.rx7club.com/3rd-generati...ometer-599220/
https://www.rx7club.com/3rd-generati...nents-1112010/

Cheers,
George

I guess it's good to fix something that's broke, but when it's working, it's does not accurately record temperatures. If it was me, I'd install an aftermarket temp gauge and not worry about fixing it.

Rousu,

Double check your 93 Body Electrical Manual for any revisions. According to my revised manual there are some test procedures that cover "Coolant Level warning light does not go out when engine is started". This may apply to your situation although your gauge is dead. It is on Pg C2-22 in my 94 Body Electrical Manual Revision.

Cheers,
George

Control Unit
 

Tracing the electrical system led the mechanic to a probable culprit: The "control unit"

The part in the car is a Naldec item that is labeled Control Unit N3Z1 18 701

Local Mazda parts says that is not in their catalogue and does not list it as anything that was put in the car by Mazda.


(If relevant, the car is automatic transmission) [ I know, but that is what it is. My previous FD3 was manual.]

The closest that Mazda had was a Mitsubishi part with the number N3A1 18 701 (note the A instead of the Z)

So:
1. anybody know if they have interchangable functions, other than their mounting bracket?
2. anybody know of a source of the Naldec N3Z1 18 701 ? parts dealer or salvage
3. Any better ideas?

thanks

TomU --- I would have to verify in more detail, but with two early recalls and a redesign on the coolant system and fans, due to over heating and resultant gas leaks and engine fires, I would be a bit leery and want to make sure the ignition-off cool-down cycle was functional. It seems that hi-temp shutdown temps were deteriorating the fuel lines. Though I could try the hammer fix...

I have no idea what this Naldec item is. What control unit are you referring to? I don't think it would be CPU#2 (located by the fuse box). Where is it on your schematic?

The engine temp gauge is separate from the fan control system. My rec is to wire an aftermarket gauge. They are a lot more accurate than the factory gauge. You can "linearize" the factory gauge, but that's too much effort IMO.

If the factory temp gauge is completely off-line then the low-level alarm would probably be too. That might be worth saving.

Temp gauge linearization
 

I did the linearization back in 2005 or so. Except for the PITA of pulling the cluster, it was reasonably simple.