Rotarypower27511

94 red touring
Problem: seat belt warning light blinks and never goes off
Buzzer stops once seat belt is buckled as expected

Hey guys, my car was sitting for many many months, when my g37 was recently slammed by a deer , I had to rely on the RX7 as my daily driver. Well the seat belt light would never go off, it was blinking during the 40 minute drive to work and back the entire time. Really annoying. After reading the electrical manual I concluded it was CPU#2. I pulled it out of the car and disassembled the circuit board from the plastic box. This is an easy job. Anyway using a good magnifying glass, I was able to isolate the problem. There were two electrolytic capacitors that were bad. One capacitors lead was completely burned in half, the other looked like it was blowing out the bottom. I believe they were labelled C2 and C5. One capacitor was 100 uF at 16v, the other was 0.47 uF at 50v. I was able to get a replacement cap for the 100uF at Radioshack. However, they didn't have the 0.47uF cap, so I had to be creative there. Since this needed to be fixed the same day so I could drive to work, I went on a cap hunt in my attic. I pulled out my old Pentium 90 computer disassembled it looking for a replacement cap. After searching every single circuit board, no luck. Then I went to the old stereo system we had from the early 90's that stopped working. It was loaded with all sorts of goodies, including 100's of caps. Sure enough I was able to find the right one. I desoldered it from the stereo and used it to replace the failed cap on CPU #2. Boxed up the circuit board, placed it back into the RX7 and viola, all is working as it should now.

This past week, my airbag light has been coming on, every time it's a different code. I'm pretty sure I probably have a similar issue with the airbag diagnostic module. I'll let you guys know how that investigation turns out. I'm seeing a lot of issues on these forums with electrical component failures. I think everyone needs to go out and invest in some good soldering tools and electrical repair tools, as this may only be the tip of the iceberg!

jkstill

iTrader: (11)

Re the seat belt light: If you are trying to maintain all the systems as part of a completely working stock vehicle, nice work.

If you just wanted to make the seat belt light stop blinking, all that is necessary is to unplug a single wire under the seat.

Rotarypower27511

Needless to say, my goal is not to mask problems like this. This is actually an easy fix. Why not fix it rather than mask it?. The effort to jury rig the light is about the same to implement a proper repair. Also, I'm an engineer. It's my nature to try to do things right.

NVMYRX-7

iTrader: (24)

Amen, I am yet to understand why people rig stuff instead of fixing it correctly. Where were you two weeks ago when I needed one?

Another thing that I have noticed is that the majority of CPU #2 issues are with 94's.

Andrew

iTrader: (1)

You can get new caps from digikey.com for pennies. That's where I got the ones I needed to fix my odometer. I think the ones in the airbag module are really big ones. I'm pretty sure there's a writeup on the forum somewhere.

Rotarypower27511

Yes, I've used Digikey before. And you are right there is a thread about replacing the caps in the airbag module. I will be referring to that post. Just got the diagnostic module out of the car. What a pain in the @$$. Unbelievable! There are three screws which secure it into the driver footwell. The top screw is pretty much inaccessible. Took me over an hour trying to figure out how to unscrew that bastard. I had to stop after I got the module out so I could drink some brew and relax to watch the Superbowl. I'll look at the circuit board tomorrow.

jkstill

iTrader: (11)

Did I not say in my post that you may or may not be trying to keep everything original and in good working order? Not everyone cares about that.

For instance, a number of FD's are race only. Mine is, and I really don't care if the CPU that controls the seat belt light is working properly or not. Since there are no stock belts in my car, it really doesn't matter.

Rotarypower27511

Jk....yes I understand your point.

4800

Mine is on its way out and it's a 94. Think I'll try to fix mine with some old stereo stuff too. Thanks for the PM.

RaceDriver7

iTrader: (9)

I figured I'd contribute to this existing thread instead of starting a new one.

Here are some photos of the fix for illustrative purposes. I ended up replacing all of the caps on the boards, since I couldn't really tell which one was bad (and they were probably all going to go bad eventually).

A good place to buy replacement caps is Digikey.com.

Here's the location of the module, in the driver's side foot well (has FD01 printed on it):



Module removed:



After you take it apart, you will find two circuit boards inside, a larger one and a smaller one.

Bigger board:



It looks like there are 6 electrolytic capacitors on the bigger board. They are those larger cylindrical components with the shiny aluminum cap on top. These types of capacitors tend to go bad over time. There are also some ceramic capacitors, but you shouldn't have to worry about replacing those.

And three electrolytic caps on the smaller board:



I think it's a good idea to replace all of the caps on both boards, so you don't have to go through this again. All electrolytic caps go bad eventually.

Also, it's generally not a good idea to use old capacitors from electronics. A new capacitor will last longer. As I mentioned, Digikey.com is a great place to order caps. You can order caps with exactly the same ratings (or better) and they are dirt cheap. If you can't find the exact same cap, you can go up in voltage, as long as it's higher than the original. If you still can't find an appropriate cap, you can go up in Farad rating by about 10% without any issues.

You'll need a soldering iron, desoldering braid, and rosin core solder. Buy this stuff at radioshack or online. You need a soldering iron made for electronics, with a fine tip, not the kind you see at automotive parts stores.

Removing the old caps is tricky. You have to heat up the leads with the soldering iron and use the desoldering braid to absorb the old solder, until you can remove the cap. Once that's done, soldering the new cap in there is easy.

Here's a pic mid-process, with the old cap on the left and new cap on the right:



Hope that helps!

CryptoPatriot

I had this problem and at first checked my board and only had one visibly leaking capacitor. So I replaced it and it didnt fix it. But I am glad I stuck to this because then I replaced them all and BAM! All is well. Thanks for the great tips!

mecman

iTrader: (11)

Nice post! Do you have a list of the capacitor sizes needed by chance?

Let me know how the airbag diagnostic module fix progresses? When I switched out my OEM steering wheel for a Mazda Nardi wheel my air bag light is now continually blinking with the code that the connection at the steering wheel is bad but I see no problems. I have even switched back to the original steering wheel air bag and I continue to get this same code.