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Horn Relay - Triumph Vitesse Mk2


Paul H
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Hi , adding relays to my Triumph Vitesse Mk2 , so far no issues with Dip & Main Beam , even got all four lights working on dipped - For MOT purposes I have an inline fuse which will isolate the inner lights on dipped if fuse is removed.

Struggling with the horn relay - Being very new to electrics I followed the same principle as the headlights ie 

1. Added additional fused 12 volt direct feed from new fuse box to Pin 30 on the relay.
2. Added earth wire to Pin 85 on the relay
3. Found the existing Purple wire from the Fuse Box , cut the wire and routed in through Pin 86 and out through Pin 87 on the relay 

This horn worked fine until I realised the relay was Hot all the time - not overhot but 20c . Im assuming the relay is hot because there are 2 direct live feeds so the relay is open & working 24/7 and consuming amps.

I searched tinternet and found this wiring diagram for an MGB 1977. The MGB layout would suit my wiring layout but being very new to electrics could anybody just check the diagram and give an opinion whether i should follow it as it looks unconventional to a newbie 

Thanks in advance

Paul 

horn-diagram.jpg.630e13882dfc37fe0cc41dcbde2fbcc4.jpg

 

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And this for comparison.

This example is very clear, not sure your wiring set-up is correct but have not studied it in-depth at the moment.

Does this assist ?????????

Regards.

Richard.

HORN RELAY - 2.jpg

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Hello Paul.

The 2x diagrams are different in respect of how the horn button plays its part.

1st diagram show the horn button to earth, so yes 85 and 30 should be joined.

2nd diagram shows the horn button acting as a circuit "completer" between 86 & 85.

It depends which way you wish to wire the relay.

Personally I like diagram 2 as it is simple and obvious, whereas diagram 1 relies on the horn earthing / grounding and 85 & 30 being joined.

Does that help ??

Regards.

Richard.

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15 minutes ago, classiclife said:

Hello Paul.

The 2x diagrams are different in respect of how the horn button plays its part.

1st diagram show the horn button to earth, so yes 85 and 30 should be joined.

2nd diagram shows the horn button acting as a circuit "completer" between 86 & 85.

It depends which way you wish to wire the relay.

Personally I like diagram 2 as it is simple and obvious, whereas diagram 1 relies on the horn earthing / grounding and 85 & 30 being joined.

Does that help ??

Regards.

Richard.

Thanks Richard. 1st diagram suits my wiring layout and I can understand the diagram !!!

Ill have a trial run tomorrow 

Paul 

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Paul, there is nothing electrically wrong with the diagram in your first post - a lot of moderns use the -ve (Earth) line to switch. 

I prefer the wiring arrangement of Richards second diagram - this one:

5a9d847b9535e_HORNRELAY-2.jpg.288a767a9d

Though it could do with a fuse between the battery and terminal 30 on the relay.

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Mark - fully agree about the fuse, hopefully it was an oversight by the artist !!

Paul - if you are installing an electric fan, the attached pdf is my own wiring diagram which I have used on all my classics past & present. If you want the fan to continue running after switching the engine off you will need to route 86 to a permanent live source.

Regards.

Richard.

Electric Fan Conversion Diagram.pdf

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22 minutes ago, Anglefire said:

Paul, there is nothing electrically wrong with the diagram in your first post - a lot of moderns use the -ve (Earth) line to switch. 

I prefer the wiring arrangement of Richards second diagram - this one:

5a9d847b9535e_HORNRELAY-2.jpg.288a767a9d

Though it could do with a fuse between the battery and terminal 30 on the relay.

The bit I couldn’t get my head around with diagram 2 was the physical wiring of the horn push as it’s earth grounded 

Paul

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One really minor criticism Richard is that the ignition live is shown with an earth symbol - I would also put all the switches  the live circuit (so from the live - either switched via the ignition or direct from the battery (And fused to suit!) with the thermal and manual switch in parallel then to the relay. But I also accept that as drawn may well be easier to wire as its only one wire from the relay and to each device and then to earth.

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41 minutes ago, Anglefire said:

One really minor criticism Richard is that the ignition live is shown with an earth symbol

Thanks Mark, never took that on board before - but yes I see what you mean.

Regards.

Richard.

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The first and second diagrams appear to work fine.  I didn't quite follow the 3rd as it is unclear to me how the horn button is wired, and I didn't spot the rogue earth symbol:

14 hours ago, classiclife said:

One really minor criticism Richard is that the ignition live is shown with an earth symbol

Personally, I would opt for the second diagram.  In the first diagram there is a permanent-live to the horns (as is the factory set up) and it is the earth that is switched.

The second diagram, in which the positive is switched, seems better.  In this arrangement, the horns will have a permanent earth, which can be achieved locally.  Less wiring, and slightly safer in the event of wires chafing (although I appreciate it's fused).

Let us know what you do....

Tom

 

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I have chosen Richard's first wiring horn wiring diagram as this layout is the closest to my existing wiring loom - In my naivety I hadnt realised  the versatility of  relays - The weak link in this diagram is the earthing which is now eliminated as hard wired an earth to an earthing point close to the dynamo ( soon to be alternator ). When all the wiring is completed ie Spots, 5 relays , horns , 42 amp cable for the alternator to battery , earthing cable I will be using loom tape to tidy things up . 

horn-diagram1.jpg.43056b2d24d2704a15c4a59d0f9c2369.jpg

Just tested the Horns and they work just fine and for anybody looking to do the same for a Vitesse MK2 the following will assist

I located all the 5 relays adjacent to the dynamo and the relays are secured to the side valence (low beam, high beam, horns, spots , heater blower ( replacing existing blower with a fan from a Nissan Micra) - I chose to use relay carriers as these look better and tidier wiring and swapping out relays is a lot easier .
The Horn Switch Wire is Purple & Black - There are 2 to choose from , Choose either expose loom & cut either wire & extend if necessary to Pin 86 
The other end of the cut Purple Black wire is not required so can be taped up 
Find the loom exit point for the 2 Purple and Blacks ( near to nearside headlamp ) cut and seal as not required as I decided to use new wire for the horns ( Most of the wiring at the front bonnet area was pretty rough so changed where necessary though still kept bullets though these were all renewed 
I added new 17amp Purple thin cable from Pin 87 on the relay to the nearside horn and then across to the offside horn 
I added 17amp thin Black cable to the second connection on the offside horn , linked to nearside horn , then onto earthing point close to dynamo 
Lastly locate the  Purple wire in the exposed wiring loom ( where the 2 purple black wires are ) cut the purple wire and connect / extend to Pin 30 
The other cut section of the purple wire is not needed so can be taped up 
The Purple wire exits the loom near the nearside lamp , cut and tape up 
Add linking wire from Pin 30 to Pin 85

Hope this helps - Thanks for all input - very much appreciated 

Paul 

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Excellent news Paul, very well done and thanks for sharing the fitting sequence.

I note you mentioned 42amp alternator cable - you may want to consider 70amp as it will handle fully, with spare capacity, whatever your intended alternator output is going to be (perhaps 18ACR ??) and will of course give you extra capacity in case you increase the output of your alternator in the future. 

Personally I think 42amp cable is a bit close to the cloth.

I look forward to hearing your additional electrical updates.

Regards.

Richard.

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Hi Richard re Alternator purchased a Stealth Dynomator   rated at 45 amps which has same profile as Lucas C40L so can use same brackets, fan belt  etc . The logic of 42 amp cable was this is in addition to existing dynamo cable which is 25 to 30 amps - Is my logic of adding the 2 cable amps capacities together correct ? so close to 70 amps  

Thanks again for your assistance 

Paul 

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Sorry Paul, I'm probably having a dull moment here.

Are you running 2x cables from the Stealth unit to the battery / solenoid ??

Regards.

Richard.

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1 hour ago, classiclife said:

Sorry Paul, I'm probably having a dull moment here.

Are you running 2x cables from the Stealth unit to the battery / solenoid ??

Regards.

Richard.

Hi Richard - yes im planning to run an additional 42 amp cable from the Stealth unit direct to the + Battery 

Paul 

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1 minute ago, classiclife said:

Okay Paul and I presume that the other cable is running from the Stealth to the solenoid ??

Regards.

Richard.

Hi Richard , yes the existing dynamo cable is transferred direct to the stealth 

Paul 

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Just been looking at their wiring diagrams.

So the RB340 is now fully redundant ??

If that is the case, why not run a single 70amp wire from the Stealth to the battery or solenoid ??

Regards.

Richard.

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If you replace the cable, I would go for welding wire - because its nice and flexible and is robust.

Something like this https://www.ebay.co.uk/i/371232433191?chn=ps&adgroupid=54682298551&rlsatarget=pla-466931245167&abcId=1133906&adtype=pla&merchantid=114936511&poi=&googleloc=1006524&device=c&campaignid=1058607774&crdt=0 would be my choice (They do red too) - though I can't vouch for the quality - its the first one that came up!

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Paul.

If you do decide to go the 70amp route, personally I would and have done so, you need Thinwall which provides flexibility and of course saves weight.

I use this company (ALM-ES) all the time for my electrical requirements and quality + price is spot on. What ever colour wire code you need they have it and in all the various cross-section ranges.

Although you have done your other cable, I would suggest you have a look at this cable which is the one I have used, just a suggestion:

https://www.ebay.co.uk/itm/10mm-sq-Automotive-Marine-Battery-Cable-70Amp-All-Lengths-Black-Red/221419178181?hash=item338d9c88c5:m:mSMhZNJFWE1HrKigriH1tOQ

Regards.

Richard.

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