"warmed" up solder points, still no horn
 

ok so i my horn doesn't work so i looked around and all i found was to re-solder the solder points on the cpu. well i did that, and my horn still doesn't work. i hear the relay clicking under the dash when i hit the button, but the horn wont go off, what now?

try checking the plug contacts for the actual horn. the horn is underneath the front relays and stuff in front of the radiator, etc. if the relay is clicking the i'd assume the CPU is doing its job because the horn has a relay and its after the CPU if i'm not mistaken.

try checking the horn for continuity/ground, then check the horn itself, also just because the relay clicks does not mean that its still good (common misconception) this means that it is getting signal from your horn button, it could still have burned the internal relay contacts therefore allowing no juice to flow. get a cheap multimeter if you don't have one already and actually troubleshoot the relay, the horn, and its ground.

if the relay clicks (please make sure its the right one clicking) than the switch itself is OK,
next check to see if the relay is getting through put power there should be 12 volts at 2 points (on the relay) when you hit the horn button, and only one when you release the button

2 points are
main power in (through put power)
ground signal from horn button
power going out to horn

when you release the horn button there should only be one that would be the main power into the relay (through put power)

if you have no main power, then you have a bad connection/fuse somewhere
if it clicks than your signal from horn button is OK
lastly if you have no power comeing out of the relay and the other two are good, then the relays internal points themselves are burned over, and it needs to be replaced also if it doesn't click and it is getting a good ground signal from the horn button then you need to replace the fuse.

if all of the above is good, then you need to check the horn itself, check for a good ground set multimeter for continuity and check ground, surface rust can stop you from getting a good ground, also check all of your connectors between the horn and the relay for corrosion.

this is a general overview that coverw 99% of the cars on the road. having never had a problem with the horns on any of the mazda's I have owned i would assume that it is the same style but feel free to correct me.

also I sincerely doubt that the horn signal travels through your computer ;)

page 286 in the Haynes Mazda RX-7 86-91 Manual

You can trace where the current for the horn goes with that wiring diagram...and you will see that it DOES go through the CPU. I think I posted in your last thread about this problem and when I had the problem...all I did was resolder the CPU and I think removed and cleaned the steering wheel contacts and everything worked fine again.

Good luck.

**EDIT** There is also a 20A fuse that is needed for the horn to work..so make sure that all your fuses are good.

Just re-heating a solder joint is just about as useless as blowing on it with your mouth.

To re-solder you must first remove the old solder (preferablly with a solder sucker), then flow new solder in.

Chances are if you are hearing the relay click, you didn't get the output wire to the horn re-soldered. This is the Green/red wire coming off the large plug on the CPU. An easy test is:

Does the green/red get 12 volts on it when you press the horn button or ground the Green/Orange in the large plug in the CPU???

If no, Bad CPU, Bad Fuse.

If it does (but the horn does not honk), then you have a Bad or disconnected Horn.

BTW, if you press the horn button and do not see ground on the green/orange wire in the large plug of the CPU, then you have a bad button or steering wheel connection.

if the relay clicks, try jiggling the wires that plug into the CPU, it worked for me!

That would be we said to resolder the solder points in the CPU.

this is gonna sound like a really retarded question, but where is the CPU located... is it what is right next to the dead petal? also is the CPU equivalent to ECU? will the car start with out it? i need to get a bood for this car.

ecu's on the driver's side. Pull back the carpet, remove the metal shield, and it's right there.

But the when people are talking about the CPU its the same as the ECU?

No!

Pull the plug off the CPU. Jumper 12 to the green/red wire. The horn should sound off. IF it does not, it's not the CPU but the wiring b/t the CPU and the horns.

If the horn sounded off, then put the plug back on. Run a ground to the backside of the green/orange wire. The horn should sound off. If it did not, then there is a CPU problem. If the horn DID sound off, then the problem lies b/t the green/orange wire and the horn button.