Electrical help with air horn compressor
Electrical help with air horn compressor
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Discussion

eunosrd

Original Poster:

5 posts

93 months

Sunday 24th December 2017
quotequote all
Hi,
bought a set of Dixie horns for my car last year, they run pretty slow so I bought a DC boost converter (to up the voltage onto the compressor) which I thought would speed it up.
Wired it all up, tested the booster across the battery and set it to 16v to see how that went, but when I attach the live out from the booster to the compressor, I only got 8-9v fluctuating. No matter how I adjust the boost converter all I can get is 8-9v when it's connected?
Any ideas?
Cheers

LordLoveLength

2,188 posts

147 months

Sunday 24th December 2017
quotequote all
eunosrd said:
Hi,
bought a set of Dixie horns for my car last year, they run pretty slow so I bought a DC boost converter (to up the voltage onto the compressor) which I thought would speed it up.
Wired it all up, tested the booster across the battery and set it to 16v to see how that went, but when I attach the live out from the booster to the compressor, I only got 8-9v fluctuating. No matter how I adjust the boost converter all I can get is 8-9v when it's connected?
Any ideas?
Cheers
They take quite a bit of current to run - what current is your boost converter able to supply?
I’d suggest it isn’t up to the job.
The horn compressor is designed to run from 12v - if it is running slowly then is it getting the full 12v when wired directly? If your supply cables are too thin it won’t get the full supply.

Also those things need oil in the compressor- has it got any?

eunosrd

Original Poster:

5 posts

93 months

Sunday 24th December 2017
quotequote all

Thanks for the reply!
That's the booster. It says 6A but I'm not sure what the compressor draws.
I've got it on the original horn live, however haven't tried it directly across the battery.
It does have oil in it as well

LordLoveLength

2,188 posts

147 months

Sunday 24th December 2017
quotequote all
It will take a bit more than 6A I’d have thought 10 - 20A or so.
Connect it without the converter and measure the voltage at the terminals when it’s running.
You may need a relay feed from the battery.

bearman68

4,886 posts

149 months

Sunday 24th December 2017
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Horn fuses are usually 25a. Would have thought air horns would need more again.

paintman

7,822 posts

207 months

Sunday 24th December 2017
quotequote all
I'm presuming you've established that they work normally when connected directly to a battery & the unit itself isn't faulty.

Remove connector from +ve terminal of the compressor (assuming you're negative earth) & try a heavy gauge wire or jump lead direct from battery +ve to the compressor +ve terminal. This obviously bypasses the vehicle wiring & horn push.
If it now works normally the vehicle wiring is the problem. May well be too thin & needs uprating - preferably through a relay and an appropriate fuse as suggested so it has full battery voltage.
If it doesn't then try the lead from the compressor -ve to battery -ve to ensure the issue isn't a bad earth.

Did the instructions that came with the horns give any details or recommended wire gauge?

Problem with a thin wire is it can't carry sufficient power.
As an example my RRC fuel pump (12v) stopped working. According to the multimeter there was 12v present throughout the system. Wiring the pump's live & earth via its connector directly to a spare battery made the pump run normally showing no fault with the pump.
After a bit of headscratching I used a headlight bulb with one side connected to earth & a wire to a pin on the other. The bulb provides a load.
Using the pin to test various points on the wiring lit the bulb until I checked the connector on the end of the loom.
Bulb didn't light even though m/meter said battery voltage was present.
Turned out the very end of the loom wire had corroded & only a couple of strands of wire remained.

Whilst you're only using them for short periods if the wire is too thin for the current it will get very hot very quickly - think of thin jump leads - & you risk fire or the melting of the insulator possibly causing a short.


Edited by paintman on Sunday 24th December 14:29

eunosrd

Original Poster:

5 posts

93 months

Sunday 24th December 2017
quotequote all
Thanks for the replies!
I'm using heavy gauge wire (as it was all I had in the garage)
I'll try the compressor straight across the battery and see what voltage I get at the compressor then and if it runs at the correct speed.
It was only supplied with a basic wiring diagram which I've pretty much followed (I don't have it any more)
As I remember I did put a bigger fuse in as the original one blew
if it still runs slowly across the battery, what else could I do to speed it up?
Thanks a lot

TooMany2cvs

29,008 posts

143 months

Sunday 24th December 2017
quotequote all
eunosrd said:
As I remember I did put a bigger fuse in as the original one blew
Eeek!

I was going to say "I'm surprised the fuse hasn't blown..." - fuses are sized to blow before the wiring melts, y'know.

Use the original wire (with the RIGHT size fuse!) to trigger a relay.
Dead easy. You just need to run a (FUSED!) wire from the battery.

(Except, obv, you don't need make a switch, and you're not switching lights - you just connect your current horn wire to 85)
<EDIT: Yes, you WILL need a new switch - I was forgetting it was a dixie horn set. Instant MOT fail.>

eunosrd said:
if it still runs slowly across the battery, what else could I do to speed it up?
Look at it very carefully to see if it says "24v" on it. Then bin it and buy one that's not buggered.

Edited by TooMany2cvs on Sunday 24th December 16:52

227bhp

10,203 posts

145 months

Sunday 24th December 2017
quotequote all
OP on his way to work yesterday:



Am I alone in wanting to know what a Dixie horn sounds like at half pace? biggrin

eunosrd

Original Poster:

5 posts

93 months

Sunday 24th December 2017
quotequote all
On my Mk2 Renault Clio leaving work, it sounds fantastic wink

eunosrd

Original Poster:

5 posts

93 months

Sunday 24th December 2017
quotequote all
TooMany2cvs said:
Look at it very carefully to see if it says "24v" on it. Then bin it and buy one that's not buggered.

Edited by TooMany2cvs on Sunday 24th December 16:52
It's a 12V compressor, I'm guessing it runs slow because it was a cheap-ish horn set, just thought I could speed it up

paintman

7,822 posts

207 months

Sunday 24th December 2017
quotequote all
it runs slow because there's a problem with the power delivery.