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Air Horn faults.

Posted: Sat Sep 12, 2020 20:02
by MetBlue
It's nearly MOT time so a few points to rectify.
Had reason to use the horn recently and although something happened, a horn it certainly wasn't. Checked today and the noise you hear is just the compressor running. Removed N/S headlamp and pipes are sound and fitted, but then the two pipes disappear into the nose cone.
A few questions :
Can the compressor motor run, but not generate any pressure.?
Is it possible to access the trumpets without a full removal of the bumper, radiator or the cowling?
As I write this I'm thinking I can remove a pipe and blow down it to see if I get any noise.
I did temporarily lash in the Fiams from my Elite which work. Not exactly loud, but it should tick the Mot box if worst comes to the worst.

Any suggestions appreciated.
Tony

Re: Air Horn faults.

Posted: Mon Sep 14, 2020 17:19
by tonypoll
Can you see the complete length of the air tubes? It's quite common for these to crack, and hence no air gets through. I had this on my Excel a few years ago, and replacing the plastic tubes is a pain!

Re: Air Horn faults.

Posted: Mon Sep 14, 2020 18:51
by MetBlue
I can only see the first 6" or so of 2 pipe. After that they just disappear into the nose cone never to be seen again.

When you did yours, what was involved?

Re: Air Horn faults.

Posted: Mon Sep 14, 2020 20:03
by Lotus-e-Clan
If you take off the lower radiator cowl the horns are very easily accessible.

On my 89SE at least, there are six fixings for the lower rad cowl. Two lower radiator 10 mm AF nut fixings, two self tappers into the body close by the said rad fixings, and two into the front spoiler somewhere near the Fog lamps.

The spoiler fixings (self tappers and clips near Fog lamps) were a PITA to remove and replace so, once I removed these, I replaced them with RIVNUT fixings and stainless allen screws because I often remove the lower rad cowl for most jobs toward the front of the engine.

Lack of of noise is not necessarily due to split tubes - give the horns a good INTERNAL spray with WD40 whilst operating the button (friend required) - it does wonders for the restoration of a proper HONK ..even if the original sound is still a bit like a Noddy Car honk.

As well asthe application of WD40 down the trumpets - also tap the horns with something hard- basically they seize-up due to their location within the rad 'venturi' - lots of moist air enters that front grill and gets into the horns... :)

Re: Air Horn faults.

Posted: Tue Sep 15, 2020 16:19
by Zag
I've had this previously, it was simply insufficient pressure to sound the horns. Sorted by copious amounts of gt85 into the compressor and run it for a bit with pipes removed.

Re: Air Horn faults.

Posted: Tue Sep 15, 2020 19:11
by CHRISYD
I was going to say all that too!!!!

Re: Air Horn faults.

Posted: Tue Sep 15, 2020 21:18
by Pete Boole
Is GT85 the same as WD40? That's what I squirted into mine! Worked a treat.

Pete

Re: Air Horn faults.

Posted: Tue Sep 15, 2020 21:32
by MetBlue
Thanks guys.
I have a plan now. Will remove air pump and separately blow air into the trumpets. Should be able to see what flow the pump delivers and ply it with some Lubricant.
Visiting Lotusbit's on Thursday as I need a couple of rear seat belt plates. If the pump is shot, might be a good opportunity.

If all else fails, I'll use the M8 bolt holding the air pump to mount the Fiamms for the Mot.

I need to know more about the spoiled fixing and the radiator cowl. It needs to come off for some paint attention so I can see the rivets being replaced with M5 screws.

Tony

Re: Air Horn faults.

Posted: Fri Sep 18, 2020 20:43
by MetBlue
Problem solved. Turns out Noddies horn is a lot happier being blown than sucked 📯📯..... Careful guys.... The moderator will want a word.
Don't know if it was the wiring polarity that was wrong or the pipes on wrong, but once connected correctly it honks like a good un.

Used my 240 V air compressor to work out which pipe the trumpet is connected to. My that was loud 🎺. I wonder if I could rig a 100 p.s.i. air tank in and just open a solenoid valve when I need the hooter. 🤔. That would certainly draw attention.

Tony

Re: Air Horn faults.

Posted: Sat Sep 19, 2020 21:35
by Pete Boole
Careful Tony - you might run out of things to fix and have to return to the Elite!! :lol:

Pete