Horns

prlee · Postby **prlee** » 25 Mar 2011 20:48

Simple question really. I have bought some new horns and wonder if I need to uprate the wiring. They need an 10Amp fuse. The car is a 1981 DHC.

Pete
81 Red DHC
79 Blue Spitfire

Beans · Postby **Beans** » 26 Mar 2011 01:00

Did you look at the sticker on the fuse box lid [:p]

<center>

1980 TR7 DHC (my first car, now restored and back on the road)
1981 TR7 FHC Sprint (better known as 't Kreng)
[url="http://www.tr7beans.blogspot.com/"]My Weblog[/url]</center>

prlee · Postby **prlee** » 27 Mar 2011 18:55

Hi Beans,

Have looked today (car is not at home). The fuse rating is 35amps according to the handbook but this supplies the relay.

I have a feeling that the wiring will support the horns, they are not air horns which I think need a higher rating.

Pete
81 Red DHC
79 Blue Spitfire

john 215 · Postby **john 215** » 27 Mar 2011 19:12

Hi,

35 amps will power air horns so normal horns should be fine. Any doubt pull the fuse and place a amp meter in its place, activate the horn and measure the draw.

Dont forget IF you need to uprate the fuse the wiring poss need up grading too, if you dont want the smoke to leak out !!!

Cheers John

LIVE LIFE A QUARTER OF A MILE AT A TIME!
1979 3.5 FHC(STATUS PENDING!!)

1982 2.0 DHC NOW A 4.6,ON THE ROAD NOW KICKING AR5E !!!!

Gubi · Postby **Gubi** » 27 Mar 2011 19:22

Here's the table I use as a rule-of-thumb guideline. Note that this is American Wire Gauge: I'm still not sure if these British cars use Whitworth furlong-pennyweights per fortnight or somesuch for wire diameter.

http://www.powerstream.com/Wire_Size.htm

10A isn't very much, especially considering the intermittent nature of horn usage. It looks like even 18 AWG (0.0403" or 1mm) wire would be sufficient.

-----
Tom
'79 TR7
'87 Alfa 75
'91 Alfa Spider

prlee · Postby **prlee** » 28 Mar 2011 18:04

Thanks all, my main concern was that I don't know what the wire rating is for the horns, the 35amp fuse supplies other things as well on other circuits.

Pete
81 Red DHC
79 Blue Spitfire

mb4tim · Postby **mb4tim** » 28 Mar 2011 19:04

I added air horns with three trumpets. I used the original horn wiring to trip a localized relay to a fused circuit I ran just for the horn motor. I was just too weak sounding from the original wiring. It sounds much quickly and stronger with the heavy wiring.

-Tim
http://www.morSpeedPerformance.com

Beans · Postby **Beans** » 28 Mar 2011 20:24

If they are "normal" electric horns you can plug them into the wiring without any problem.

I fitted these after market (and very loud [}:)]) horns to my DHC, plugged them in using the original wiring ...

1980 TR7 DHC (my first car, now restored and back on the road)
1981 TR7 FHC Sprint (better known as 't Kreng)
[url="http://www.tr7beans.blogspot.com/"]My Weblog[/url]</center>

prlee · Postby **prlee** » 29 Mar 2011 19:26

Thanks Beans, I will have a closer look at the wires but sounds like the wiring should be ok - I have a fire extinguisher handy any way [:)]

Pete
81 Red DHC
79 Blue Spitfire

Beans · Postby **Beans** » 30 Mar 2011 17:38

I wrote in my earlier post that I plugged it into the original wiring.
That's not completely true, I fitted extra earth wires which connect directly to the earth points behind the head lamps ...

Horns are normaly mounted "directly" to the body/earth, but I like to be on the safe side with wiring.

<center>

1980 TR7 DHC (my first car, now restored and back on the road)
1981 TR7 FHC Sprint (better known as 't Kreng)
[url="http://www.tr7beans.blogspot.com/"]My Weblog[/url]</center>

saabfast · Postby **saabfast** » 30 Mar 2011 19:38

My car only had one horn fitted when I got it, and that was pretty feeble. I bought a pair of cheap high/low horns (like these http://cgi.ebay.co.uk/12-VOLT-DUAL-TONE ... 19c447f9bc) and fitted them to the existing connectors, they even fitted the existing mount IIRC. They work well with no load problems and are pretty loud.

Alan
Saab 9000 Stg 1
Saab 9000 2.3 FPT Auto
'81 TR7 DHC

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