I am having a few problems that lead me to believe I need to resolder the CPU. I tried searching for a "how to" but to no avail.

List of problems -

-Warning lights come on randomly when ignition is on.
-Alarm doesn't work at all.
-Power mirror switch doesn't work (might be unrelated, mirrors have been tinkered with as far as I can tell.)
-Horn relay clicks, but no horn (again, could be unrelated, but the horn worked fine before I put my new engine in)
-Clock doesn't work at all
-When my lights (headlights or parking lights) are on, and I hit the turn signal, my "signals" in the cluster alternate between left and right, and the tach needle goes up and down. This is a problem with the cluster for sure, because my old one worked fine in this regard.


Like I said, I've heard of re-soldering the warning light board, CPU, and cluster, but I have yet to find a how-to. These problems seem like they correspond to what I have read is caused by cold solder joints.

Thanks in advance.

 

The clock has nothing to do with the CPU. You will have to take the idiot cluster out and resolder it.

I'm not 100% sure if all the other problems are CPU related. As for resoldering the CPU, the hardest part for me was getting the case off so that I could get to the circuit board. When I took mine apart, I first checked the connections with an ohm meter. I immediately noticed that one of the resistors was black and sure enough, there was infinite resistance across it. There was what seemed to be dirt on the PCB around the resistor, so I cleaned that off as well. I replaced the capacitor that is right next to it.

For the actual soldering part, it isn't too hard. Aaron Cake has a pretty good write up on how to solder on his site. Make sure that you lay down new solder instead of just heating up the old solder. This will probably save you time from having to re-do everything in the future.

If all else fails, Mazdatrix has CPU boards for sale on their site.

 

Best advice I can give you to keep things simple is remove and resolder the joints where the plug pins go, and go from there. If that doesn't cure the problem, you'll have to become more advanced (see post above). To know what the CPU controls, see Body Electrical Chapter in the FSM, the link is in my sig. The alarm is in a separate control box near the glove box underneath. Remember that your alarm may be screwing up because of simpler things, like switches in the door locks or door frame, hood, or hatch. Back to CPU - it controls horn, hazard, warning chimes (not lights) for lights on, ignition on and doors open and turn signal - I may have missed one. In my case, resoldering the warning light cluster plug pins (the large solder joints) cured a crazy clock and odd warning light problems. As far as your cluster, I'd put the old one back if it's an option or you'll have to tear into the new one. Tell us more about why you changed the cluster...I have a feeling you changed to a turbo one and didn't re-pin (the connections are different).

 

http://www.johnr.com/rx7faq/faq3.html

 

^^^^^^^^^excellent link!!!