Hi I have a 98 sw2 and I replaced the horn with a 2 wire unit and a relay.
It worked fine for a year and now the horn no longer works.
I verified the following:
1)Horn operates by itself
2)Horn Fuse is good
3) relay not checked because there is no 12V low to operate it
4)At the horn wiring harness,
a) 12VDC is OK
b) ground is OK
c) 12V low current BAD - it reads about 10 mv when the horn is pressed. Also there is no current. The resistance is always near open.
5) alarm system will flash the interior light but not beep the horn.


Is there a fuse for the security system that may be killing the 12V low current? Could a bad horn switch also prevent the security system from activating the horn?
Im stuck, any help would be fantastic!
Ken

 

Are you no longer using the original relay and circuit?

 

Hmmmm -- Interesting thread .....

 

Yes I installed a 2 wire horn and a relay. Everything worked fine for months. Now the horn wont work from the steering column or when the alarm is activated. It seems like the horn switch wire is not providing enough current to activate the relay.

 

The original horn circuit routes power to the horn via a relay. The +12 volts for the horn supplies both control circuit voltage and horn voltage. You mention that you replaced the OEM horn with a two wire unit and a relay. Did you bypass the OEM relay and rewire the circuit, or did you simply use the output of the OEM relay to control/drive the new horn?

 

I have to work from memory. The horn and it's relay are gone.
They have been replaced with a horn and relay. The wiring harness supplied power and ground to the relay contacts and the center connector (from the horn switch) went to the relay's coil.

I am thinking about breaking down and spending a bunch of cash on a 3 wire horn but the 2 wire setup was working fine. Im worried that a new horn wont fix things because the center lead on the harness does not seem to be doing much anymore. As I recall it delivered a low current and 12V when the horn was pressed. Not it barely shows current or voltage.

 

OK - I know you say the horn fuse is good, but check it with your ohmmeter. It's a 10A fuse located on the Underhood Junction Block (UHJB) and is connected to the "always hot" +12v source. From there, it goes directly to the horn relay (both control and power contacts). The other side of the relay control wiring goes to the horn ring, which supplies a ground when pressed, thereby completing the circuit and activating the relay. *NOTE* -- This is how the OEM circuit works.

I fail to understand why you are not picking up the +12v control voltage for your after-market relay, since on the original circuit, it was the same wire as the horn power. You say horn power is there, but horn control voltage is not ... therefore (1) wiring error, (2) open control voltage line, (3) bad horn switch (no ground when pressed)

 

Ok you work from memory ...... we have no idea what you've done leaving us with no memory of it.

 

Thanks for all the responses. My last reply may have been dropped.

Just to clear things up, I have disconnected the horn/relay that I added and I am troubleshooting the horn harness. If I can get the switch signal back then I will break down and buy an OEM horn

The 10a fuse has continuity.

The horn switch may be bad. The horn/relay combination I added did not have a diode across the relay coil. This may have killed the horn switch?

1) The only thing is, if the switch is bad, wouldn't the alarm system still beep the horn?

2) If the switch is good, is there another fuse somewhere that may be blown? (I just need to pass inspection for now)
Thanks

 

Do you have a power doorlock system? Check the BODY fuse, and the CHIME fuse (both 10A) located on the Instrument Panel Junction Block (IPJB) inside the car. Also, the remote keyless entry (RKE) may be bad