So, after I got my RX-7 back on the road, I traced a couple of problems down to what could be a bad CPU. I didn't have warning beeps (headlights on, key in ignition, etc), the theft security light wouldn't blink, and I had a turn signal that would hyper blink even with both bulbs working. I took a chance on a cheap used CPU and swapped them out. My warning beeps immediately came back, but my turn signal still hyper blinked. I considered the problem mostly solved as maybe I would need to trace down other potential issues for the hyper blinking turn signal.

The car hasn't been driven at all since then, but the key has been flipped to ON a few times for various reasons. I replaced my turn signal housing as I noticed the ground wire looked to only be attached to the base by a strand or two. That didn't fix the hyper blink either. But then, I noticed my warning beeps that had come back with the CPU swap have disappeared again.

Any ideas on if something in my car could be quickly killing the CPU? Or is this just a bad coincidence of another one going out on me? Most of the wiring into the CPU is switches so the CPU knows when to beep. The FSM is pretty thin on CPU diagnosis, the pages dedicated to it are where it's located and what connector controls what. The section for the theft deterrent unit deals with testing switches and if it doesn't operate properly to replace the unit. I know I'm going to have to do some wiring checks, but I'm curious if anyone else has experienced anything like this.

 

Not sure what would kill it immediately, but electrolytic capacitors that have leaked might be causing your problems as described. I have an old CPU in my S5 that currently doesn't support any of the warning buzzers. I've rebuilt another CPU that had several leaked capacitors but am hesitant to install it due to the return of those annoying warning buzzers.

 

The timing of it is what baffles me. We are talking a time frame of two weeks. Beeps back, beeps gone. And as annoying as they can be, I find them somewhat endearing.

Maybe I'll start by pulling the old one apart.

 

I replaced the capacitors in mine a couple years ago because I lost a lot of functionality. Its a pretty easy board to work on. You might also check some of the other components in the cpu if you see some hot spots. These capacitors are well past life expectancy, no matter which one you get. Some just hang on longer than others. I replaced the capacitors in my cpu and bypassed the rotten parts of the circuit board. That made me go and replace all the rest of the capacitors around the car as preventative maintenance. I'd recommend going through as many as you can.

 

By any chance did you replace any of the turn signal bulbs with LED replacement bulbs? That in itself would cause the hyper-blinking behavior, even with a perfectly good CPU. If you did swap out to LED bulbs, there's a pretty simple mod you can make to the CPU that involves removing one of its resistors that eliminates the hyper-blink issue with LEDs.

 

i had a vert with bad turn signals and it, surprise, was bad solder joints on the flasher board, easy fix

 

No, they are regular Sylvania bulbs. They are long life, which I have heard may cause issues. I could try to find non-LL bulbs.

All of these thoughts make me think it's just bad CPU luck. I'm going to open up the original one and see what I have. My soldering skills aren't the best, but myself and a friend did manage to replace a couple capacitors on a home theater receiver once. I guess this will be similar.

 

Well, one advantage of working from home is doing RX-7 diagnosis during a morning break. Here's pictures of the flasher module board and the main board (illumination timers, warning chimes, etc.). There definitely looks to be some suspect areas on the main board. These are from the CPU that hasn't worked since the car has been running. The CPU that momentarily worked is still in the car.

 

The e-cap that you show, right next to R40, is the one that leaked on my board too. I replaced all the e-caps on my board.

 

Yeah looks like that board needs new capacitors and some cleaning.

I didn't see anything immediately wrong with my flasher module board until a close inspection. I appear to be missing two resistors, R3 and R14. Here's a picture available on many websites of a new flasher module (this one from Mazdatrix's website):

 

The missing resistors is probably nothing to worry about. It's not uncommon for OEM electronics suppliers to build a circuit board for multiple end user applications (i.e., some that don't use the missing parts), or for in-production revisions taking place that sometimes delete components that were in earlier production pieces without revising the circuit board itself. So you may end up seeing some vacant spots on a circuit board that were marked for a component. After giving up on trying to fix my CPU and buying a new one from Mazda via Ray Crowe, When comparing my new & old CPU, I noticed that the circuit boards and components on them had some visual differences - but the new one is still form/fit/function equivalent to the old one.

 

When you replace the rotten capacitor and clean up that area of the board, it would be worth going ahead and replacing the corroded resistors, and voltage regulator if you can. The resistor next to my bad capacitor just crumbled into dust. Also check that the traces are still good. You may have to add some bypass wires to get around if one of the traces got eaten.

 

​​​​​​​Hmmm, interesting. I guess it stood out to me since those are the only two spots missing components and they are visible in a picture of a "new" product. The only other places missing something is a spot on the other board, but is pointed out as being reserved for FC66 (convertibles).

 

I just looked up your thread on an S5 CPU fix. I think I have enough to fix this thing now as long as my soldering skills are up to par!

 

>> You wrote: "...I appear to be missing two resistors, R3 and R14."

Yeah, I want also reiterate that not all boards are the same. Apparently, there have been some circuit modifications (i.e., improvements) over the various generations of circuit board development.

 

I have an update. I replaced every capacitor on the CPU board and two resistors that were taken out by leaking electrolytic fluid. I also replaced the flasher module board with a brand new Mazda part so as to start from what should be a known working part there. I also used JB Weld to fix the broken plastic tab that hangs on the chassis stud.











Plugged everything back in and...


However, right turn signal still does this:


So, still something happening there that maybe (?) isn't CPU/Flasher Module related at this point.

 

I tested a couple other things that the CPU is responsible for. Moral of the story - replace your CPU capacitors!





I put in that door handle keyhole light in hopes I would one day get it to work. That day is now.

 

Regarding the right turn signal, maybe a bulb is burnt out since that can cause the symptom that you're showing.

 

I've walked around the vehicle and verified both are working. I'm going to check grounds, especially at the rear. I've had lots of issues back there and corroded terminals was one reason some brake lights didn't work. I thought I had sorted all that, but I feel like I've been over almost anything else that could cause that.

 

Good deal bud!

 

Your thread from a couple of years ago was a major help, so thanks!

 

neat! its on the list to do mine.

i was going to say though that my washing machine only works when the control board is physically hot, i think i have a bad trace somewhere...