electrical possible cpu?
 

I have an 86 TII and my horn doesn't work. I tested the horns and they work. All wires to and from horn and horn switch are fine. The cpu is getting power could the horn relay be screwed? I have an S5 GXL as a parts car right now could i use the cpu out of that? I've run out of ideas any insight would be appriciated.

the horn circuit on the S4 and S5 are different as far as CPUs, and you could not interchange the two.

are you getting 12 volts out on the horn wire (green/red at CPU's large middle plug) when honking???

The 87 Turbo uses a FB05 CPU which I do have rebuilt ones instock on my webstore if infact your's is bad

Go to the CPU. Find the GREEN/ORANGE wire on the plug.

Get a piece of wire and bare both ends. Stick one end in the back of the GREEN/ORANGE wire while the other end is touching a known ground. The horn should blow proving the CPU part of the circuit is ok.

If it blows, then you need to find out why horn switch is not putting a ground on the GREEN/ORANGE wire.

This is done with everything connected up. The CPU plug is on the CPU.

The GREEN/ORANGE wire is the second wire from the end of the connector. Series four cars.

The horn also won't work unless the STOP fuse is good. It's a 20a fuse inside the car. It feeds the GREEN/WHITE wire on the CPU'S plug. Are your stop lights working? Fuse good then.

nope not on that wire i get no resistance between that wire on the cpu end and the horn plugs and no voltage gets to the horns.

awsome i'll try that in the morning.

If you pull the CPU's plug off, and jumper a wire b/t the Green/White and the Green/Red wires on the plug, then the horn should honk. If it does not honk, and the plugs are on the horns, then either the STOP fuse is kaput or there is a open in the Green/Red wire from the CPU to the horn plugs. Series four CPU.

Green/Red is on the end of the plug. The Green/White is the third from the end. Top row.

well that settles it. i get voltage when i jumper green/red and green/white. When i ground the green/orange i get nothing. i guess i stop by the local auto recyclers tomorrow. I can use the cpu out of any S4 right? GX, GXL and such.

No, you want a FB05 CPU.

It is only found on 86-88 Turbos, GXL, and some verts (the ones with leather seats).

OR send your to ICEMARK and let him resolder the connector/CPU.

I, a long time ago, had a non-working horn. Jumpering 12 v to the horns from the plug made the horn honk. I was getting a ground on the GO wire when I pressed the horn switch. I was getting 12v on the GW wire. So I took the CPU out of the car and did some reflowing of the solder joints, I THINK at the connector area of the CPU where the electrical plug attaches. It's been a while. /