i have an 87 t-II, and i cant get the horn to work, i have gotten a new "cpu"(the black box that controls the blinkers, brake lights, and some other small things. For some reason there is power going into the cpu, but no power coming back out of it going to the steering wheel. somtimes there is power but it is very inconsistant. Should i have power coming back out?, or could it be a problem involving the theft control(which i am not sure if is still hooked up)? is there a way to repair the cpu? is this a common problem? because both my cpu and the other one i got both seem to have the same problem. Any help on this would me much apreciated. i need my horn to work to get the car inspected, and i want to drive it REALLY REALLY BADDDDDDD. Thanks.

 

bad CPU based on your description as long as you are testing with a digital multi meter.

I have rebuilt CPUs for that car. It uses the FB05 CPU. See my website below for details.

You can also try rebuilding it yourself. You would want to remove all the solder from the joints where the plugs plug into the circuit boards, and then flow new solder in. I would also recommend replacing the relays.

 

I had that same problem a few years back my horns just quit working one day.

just to check since it is fairly easy fix

I had blown the diod you could see that it had blackened, so if you just look over the couple by the horn relay to see if that is the problem. Also they acted up on me a bit after that all I did was hit the contacts on the relay with like 220 sand paper haven’t had a problem since, you could see them arcing a bit before I did that.

don't know if that helped, but good luck

 

The steering wheel horn buttons put a ground on the relay inside the CPU.

Backprobe the Green/Orange wire with a wire that is grounded and the horn will/should work.

If it works the problem lies in the steering wheel horn button assy.

If the horn does not work, pull the plug off the CPU. Jumper a wire b/t the Green/Red and Green/White. The horn should work because it's bypassing the CPU relay.

Horn still not work? Make sure there is batt voltage on the GW wire. Got batt power? Make sure the horns have the plugs on them. Still no horn? Ohm out the GREEN/RED wire from one end to the other end. Wire good? Give up and buy a air horn with a bulb to press.

 

I was going to mention the horn button, since i discovered that the left button on the wheel works just fine while the right one does nothing. As long as it works, i'm not going to tear into it unless i have excess time to kill.

 

Thank you, i didnt realize it had to be an fb05, i got an fb01 and it didnt work. so i will try to locate another fb05. any model years that you know definetly use an fb05? so i know what to look for at junk yards.

 

I got another fb05 from a junkyard and it worked. thank you. , now i just need to fix the 3800 rpm bogging problem.........ugh.....

 

BTW, the FB01 will work for replacing a FB05, you just won't have the door or ignition key lights working.

That's the only real difference... they use the same plugs, same body, just the FB01 does not have the timing circuit for the key lights that the FB05 does.

 

oh, alright, that is good to know incase i ever have to buy another. and if i need electronics like that for my car, i will definetly be going to your website, thanks.

 

i thought i blew my CPU..turned out to be the horn wasnt grounded well enough...
duhhhh

 

good info.

 

would this be related to other elec probs too? my break lights dont work, at all, and my right blinker doesnt work, AND my brights get stuck on..