[goaterguy]

This morning I tried driving the Volt and after 3 mph the horns stars honking dependant on the speed, the faster I went, the quicker the horn bursts until about 15 mph where it just becomes a solid honk.

You can imagine how much my neighbors love me now...

I removed the horn fuses and the relay, tested the car, battery only, with ICE running etc. No issues nor codes.

Found that the horn relay is a hella solid state relay, also found this:

While testing the relay I noted that there were 10.96 volts running though 85 without grounding 86 (open), is that normal?

If I ground 86, I get the normal 12 volts.

Can anyone confirm this before I spend $40 on a relay?

Hoping the relay is bad and any ghost signal is triggering it.

Funny I ordered a VCX Nano a few days ago, looks like the car found out and is saying "challenge accepted!"

 

[Manitoba Keith]

I would suggest that you remove the relay, attach voltmeter to 85 (Gnd) and 86 +ve. While driving, have a helper watch the meter and see if you get pulses as you hit 3 MPH and then a solid +12 volts when you reach the solid honk speed. If you do, I would think it might be further back in the control circuit. Could even be a vibration induced horn button press - But I doubt it.
Edit: Obviously the socket not the relay

 

[goaterguy]

That's a good test, I will perform it and report back.

 

[goaterguy]

Sent an email to Hella.NZ with my relay testing results and to my surprise, they responded saying that the relay may be faulty. Still need to get in the back while my wife drives the car to confirm the connector is acting properly.

Can anyone test their horn relay to confirm results? It's in the driver's side compartment in the trunk, no need to remove anything else.

 

[somms]

Sent an email to Hella.NZ with my relay testing results and to my surprise, they responded saying that the relay may be faulty. Still need to get in the back while my wife drives the car to confirm the connector is acting properly.

If your pedestrian alert, triple-honk vehicle left on reminder, charging confirmation, ect. noises on your Gen1 still function normally, this would indicate the solid-state relay is operating correctly and I would be inclined to guess your BCM is somehow incorrectly translating the vehicle speed changing to increasing modulation of the momentary ground signal leaving the BCM and activating the pair of horn(s) thru the relay.

If the other horn alert(s) are working fine you may be looking at replacing and/or reprogramming your BCM...

 

[goaterguy]

Yes, but the horn was making a slight sound when unlocking the car which is not normal. I just want to rule out the relay as the problem. If the relay is still sending 11v out when open (and this is confirmed abnormal for this relay), it could still be the problem.

 

[somms]

You could try to isolate pin#4 by taping this pin off on the relay with electrical tape and then reinsert it back into the circuit, this would eliminate the relay as being the cause if all possible horn noises should then cease completely...

If this is the case and taping off pin#4 eliminates the horn noises, you would then have to troubleshoot why the momentary ground signal which energize the relay are getting to pin#4...

 

[goaterguy]

Just to close this one out, ordered a new relay for about $33 on Amazon, received it this afternoon and installed it during lunch.

Problem solved. First out of pocket repair in 4.5 years. Luckily I was able do diagnose the issue, I think that would've added a few hundreds to the cost if I had gone to the dealer.