1971 Ghia Horn Diagnosis

[sped372]

Latest work order calls for diagnosing a wonky horn on the Ghia. Was operable until a couple days ago.

Symptom: It doesn't blow when you press the horn ring. When you let up on the horn ring you get a brief, quiet "ngh" out of the horn for a split second.

I ran out of light last night but here's the clues thus far. I'll add more as I get into it further.

1. The Ghia actually has two horns, wrapped by a rubber boot thing, under the spare tire in the trunk. There's a relay in the trunk that appears to send power to the horn-pair when it's low-current loop is energized by the horn ring at the steering wheel.

2. Connections look crusty. I recently replaced the hood seal but I imagine a damp environment in the trunk led to corroded terminals.

3. VM between low current (+) side of relay and chassis reads 12v when the horn ring is pressed.

4. VM between (+) side of horn-pair and chassis reads 8v when horn ring is pressed.

5. Resistance is ~150 ohms between relay ground terminal and chassis.

Sounds like a bad ground to me. Shouldn't resistance be basically nil between any ground point and metal on the car? Or, could the innards of the relay be corroded leading to more resistance?

Next step will be cleaning all of the terminals and retesting everything. I'll update the post as things progress.

[dtrumbo]

Remember that the horn button is providing the completion of the circuit (ground) for the relay. Theoretically, there should be infinite resistance between the switched-ground terminal (85) of the relay and the chassis when the horn button is untouched. Pushing the horn button should complete that ground connection, energize your relay and horn-blowing merriment should ensue. There is also an inline spade connection between terminal 85 of the relay and the horn button that might need to be looked at.

All of that said, if you're getting 8v to the horns when the button is pushed, I would think the relay is working. The low voltage could be caused by corroded terminals on the relay or the horns. Another possibility is one of the horns is shorted drawing down otherwise 12 volts to 8. You can unplug the horns one at a time and see what changes.

Do you have access to this?

http://www.thesamba.com/vw/archives/inf ... 71ghia.jpg

[sped372]

corroded terminals on the relay

Just based on visuals I'm thinking this is the culprit. I picked up some dielectric grease today at lunch and shall endeavor to release the electrons.

[sped372]

Thar she blows. A bit of sandpaper and rejuvenated crimp connections yield two functional horns. Tief and Hoch both tootle merrily now.

[Amskeptic]

Tief and Hoch both tootle merrily now.

"Tootle merrily"? How is that?
My factory spiffy BobD horn honks like a goose with a head cold.
I lean on the horn button in an echo chamber parking garage, and pedestrians barely break stride with puzzled looks,
"What was that sound?"
"I think it was a goose."
"Didn't they already migrate?"
"I dunno, maybe it was a duck."

[sped372]

You really have to hear the two-pitch Ghia horn to appreciate it. I'll agree that the Bus and Bug horns are somewhat less-than-commanding (I love the sound, though) - the two-note effect is pretty cool, though.

"Merrily" was intended to describe the vigor with which the horns perform their duties, not necessarily the conveyed emotion of the noise. Prior horn-ring-pushing actions would result in the horns grudgingly emitting a labored, sickly tone whereas now they jump right to attention.