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Has anyone had experience of Red Rotor Arms?
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theopenroad



Joined: 06 Dec 2007
Posts: 17
Location: Warwick

PostPosted: Sun Mar 14, 2010 4:14 pm    Post subject: Has anyone had experience of Red Rotor Arms? Reply with quote

I run a fleet of 9 classic cars which I hire out, so statistically each year my cars do the equivalent of nine years motoring.

Therefore I see a fair number of problems that may not occur to the average classic owner on a regular basis.

Over the past few years I have had a few breakdowns due to rotor arms failing. I now keep spare rotor arms in all the cars.

This is no great problem if you own and drive the car yourself, but is very inconvenient to customers. I don't expect (or want) them to tinker around under the bonnet. All the cars have RAC support so the RAC can come out and fix the problem, but this may still inconvenience the customer for 1 to 2 hours.

I have bought rotor arms from the main suppliers like Moss and Halfords and still occasionally have problems. I doubt I will ever reach the position where rotor arms never fail but I am keen to find some better ones.

Does anyone have experience of using the 'Red Rotor Arms' from the Distributor Doctor? Are these any better than the normal ones? Has anyone used these for either any length of time, or for high mileages?

Or does anyone know of any other suppliers of 'better quality' rotor arms?

I have a mix of Austin Healey, MG, Jaguar and Triumph cars for hire so need rotor arms to fit the normal 4 and 6 cylinder distributors.

Thanks
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peter scott



Joined: 18 Dec 2007
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Location: Edinburgh

PostPosted: Sun Mar 14, 2010 5:07 pm    Post subject: Reply with quote

Hi Tony,

See http://www.oldclassiccar.co.uk/forum/phpbb/phpBB2/viewtopic.php?t=8225

Peter
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theopenroad



Joined: 06 Dec 2007
Posts: 17
Location: Warwick

PostPosted: Sun Mar 14, 2010 5:20 pm    Post subject: Red Rotor Arms Reply with quote

I had spotted that thread, so thanks for being on the ball, Peter.

I would still be interested to hear of anyone else's experiences with 'Red Rotor Arms'. Particularly long term use or high mileage users.

Reliability is key to me providing a high level of customer service in my classic car hire business and while the cost of these items isn't high I would like to hear from customers that they do the job.
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Phil - Nottingham



Joined: 01 Jan 2008
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PostPosted: Mon Mar 15, 2010 12:13 am    Post subject: Reply with quote

I have just bought 3!
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ukdave2002



Joined: 23 Nov 2007
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Location: South Cheshire

PostPosted: Mon Mar 15, 2010 9:07 am    Post subject: Reply with quote

Not had any expirience of the "red" arms but have had 2 black ones (from Halfords unsure of make) fail with exactly the same symptoms;

Car will start from cold fine , then after about 10 miles looses power to the point where it can not be driven (feels like fuel starvation) if you stop the engine it won't start untill its cooled down. I thought it was fuel vapourisation at first, but no was a rotor arm fault.

I don't know if you have an engine scope? if you do its easy to detect failure way before it becomes a problem.

Dave
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theopenroad



Joined: 06 Dec 2007
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Location: Warwick

PostPosted: Mon Mar 15, 2010 9:50 am    Post subject: Red Rotor Arms Reply with quote

I don't have an engine scope but I have a basic spark plug tester which clips one the spark plug and glows orange if there is a spark.

So it is an easy enough problem diagnose.
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Roger-hatchy



Joined: 07 Dec 2007
Posts: 2135
Location: Tiptree, Essex

PostPosted: Mon Mar 15, 2010 10:46 am    Post subject: Reply with quote

Just as a matter of interest
Does anyone know when these rogue caps started to come on the market.

In the early 70's my DLM, (E93a engine), had the same problems, well the same symptoms in traffic.
On the open road while on the move no problem.
In traffic for any length of time and it would do the same, cut out till cool again.

As with most I always assumed a fuel problem.

Roger
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therobbiesmith



Joined: 18 Oct 2009
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PostPosted: Fri May 28, 2010 6:42 pm    Post subject: Red Rotor Arms Reply with quote

Sorry to be so late adding a comment.

My 1965 Mk1 MGB used to fail in traffic on hot days, like others I attributed this to fuel vapourisation until I read Peter Scott's information on red rotors and bought one from Distributor Doctor (For less than £7). I've been stuck in traffic several times and recently in hot weather without the slightest problem since fitting one.

I hope this belated contribution helps.
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Nic Jarman



Joined: 05 Oct 2008
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PostPosted: Fri May 28, 2010 11:03 pm    Post subject: Reply with quote

The rotor arm in my Midget is blue, I use it just about everyday and have had no problems. Good luck.
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therobbiesmith



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PostPosted: Sat May 29, 2010 11:00 am    Post subject: Red rotor arms Reply with quote

Lucky you, I've never heard of a blue one but the problem is apparently caused by the carbon content of modern black plastics exacerbated by poor manufacture of the rotor arm. The red one is a much tighter fit, has a much larger contact area and lacks the brass stud on top. All of which makes it much more effective.
If yours is blue, it obviously lacks the carbon which causes much of the problem, making modern black rotors poor insulators.
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theopenroad



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PostPosted: Sat May 29, 2010 12:29 pm    Post subject: Red rotor arms Reply with quote

Thanks for the update. I hadn't realised it was the carbon content in the plastic that was part of the cause. I just thought it was bad plastic which developed hairline cracks, making it easy for the spark to find a route to earth.

Tony
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therobbiesmith



Joined: 18 Oct 2009
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PostPosted: Sat May 29, 2010 4:45 pm    Post subject: Red rotor arms Reply with quote

If you look at Peter Scott's contributions he explains the whole thing much better than I can. The carbon content makes the plastic conductable and causes the charge to escape down the main shaft of the distributor to earth in the block. The brass stud/rivet on the top of the arm adds to this problem too, but read Peter on the subject.
I am now concerned as Andy Melville at Motorline in Fyrle is fitting an electronic distributor and coil to the B next week and I'm not sure how good the rotor arm will be in that combination - we shall see. . . . .
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Nic Jarman



Joined: 05 Oct 2008
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Location: Stoke by Clare, Suffolk

PostPosted: Sun May 30, 2010 9:57 pm    Post subject: Reply with quote

I had a little play with the Midget engine so I thought I would post this photo

It clearly shows the brass contact in the rotor arm has NO stud/rivet holding it on but it is moulded into the arm, this gives good insulation. If the material that the arm is made of is the problem then one would expect it to fail imediately. I cleaned the inside of my dizzy not too long ago and yet there is some crud back in it already. I still think that the stud/rivet may well be the problem as there is no insulator between it ( electricly hot ) and earth ( 0v ) where as my rotor has a big lump of plastic between them. A small amount of contamination would allow the stud/rivet to track to earth. The old black rotors did not seem to be a problem but then they did not have stud/rivets in them.
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therobbiesmith



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PostPosted: Sun May 30, 2010 10:45 pm    Post subject: Reply with quote

And here's my own comparison of red and black.
http://i910.photobucket.com/albums/ac303/therobbiesmith/Red%20Rotor%20Arm/001.jpg
The difference is clear, add that rivet/stud to the conductive high carbon plastic and it's a wonder the black ones work at all.
Bring back Bakerlite!
Or stick to any colour but black.
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Jim.Walker



Joined: 27 Dec 2008
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PostPosted: Tue Jun 01, 2010 4:16 pm    Post subject: Reply with quote

No one seems to have mentioned the time honoured way of checking the rotor arm, which is worth knowing if only to stop motorists chasing suspected red herrings.

Disconnect the HT coil lead from the distributor and remove the distributor cap. Make sure the points are closed, hold the lead end just clear of the rotor arm blade and flick the points. If you get a spark between the lead and the rotor arm it is a "dud". If you get a "bite" off the coil lead don't blame me because you have proved that is too!
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