Indicator 'Flasher Can' erratic operation

[enigmas]

Ok I need to talk to the electrical gurus who frequent this board.

The flasher can on my nominally original MK3 P5 Coupe started playing up. Eventually it stopped working completely. I purchased a replacement unit and fitted it. (The unit was positioned inside the RH instrument pod below the dash. (It has been in this position since I acquired the car 18 or so years ago.)

When I fitted the new unit and tested it, it operated at an excessively fast speed. This was a fully electronic unit (integrated circuits). All earths and power feeds are clean.
I then substituted another older unit which I acquired from a wrecked vehicle. This has small coils inside and is mechanical/electrical. When I connected it, it worked but also 'flashed' too fast. Internally on this unit there is a small spring which I tweaked (less tension) and the unit operated close to the desired 'flash' rate.

The 'original' flasher can that I removed (in car for last 18 plus years) was a
Bosch P123 Electronic Flasher
12 volts, Max 30A, Up to 14 lamps.
The Terminals are marked: P, X, L

The fully electronic unit (modern) is a
Tridon EP35/FET13
Heavy duty 12 volt.
The Terminals are marked: 49+, 31-, 49A

The Problem:
When I switch on the headlights or a power feed (heater fan) the unit flashes at a faster rate.

(Is there any relationship between the flashing speed of the unit and the 10 volt dash instrument regulator?)

Suggestions welcome guys. ~ Vince

[Warwick]

Vince, it's a long time since I've had one of these apart, but here goes.

The old style electro-mechanical flasher relies on the heating and cooling of a length of resistance wire that is held taught by a spring. When you operate the indicator switch, current passes through the wire and it heats up and expands; growing in length and moving a contact. The heating (lengthening) and cooling (shortening) of the wire controls the opening and closing of the contacts and the contacts determine the heating and cooling of the wire.

The load placed on the circuit also affects the current passing through the wire and so determines the rate of heating and cooling. This is why adding a 3rd bulb to the circuit by connecting up a trailer causes the flash rate to slow. Conversely, removing a bulb from the circuit (having a blown globe) causes the remaining bulb to flash faster.

All this is fairly crude and the variations in battery voltage that occur in a car cause no noticeable change to the flash rate.

Then we have the electronic flasher which is simply a solid state timer device designed to open and close an internal relay at a fixed rate regardless of what load is connected to it. I don't know for certain, but I would expect these to have built-in voltage regulation so that they were unaffected by voltage fluctuation caused by various other loads and the charging system.

So in answer to your question; what you describe doesn't make sense.
I would expect an electronic unit's rate to be unaffected by the supply voltage(within the normal range) and unaffected by the load.
I would expect an old-fashioned electro-mechanical unit to be unaffected by the supply voltage but affected by the load. If this type flashes faster and is not faulty or damaged, it would have to be caused by a lower load - a blown globe.

I can't see how other parts of the electrical system (headlights, heater fan) can have any effect unless ...

Coincidently there is another fault in the system clouding the symptoms.

Or, a fault has occurred with the flasher can that is causing the symptoms - although the odds of all being faulty seems to rule this out.

Or the dear old P5 doesn't use a typical electro-mechanical unit and it IS sensitive to the supply voltage - and so is your electronic unit.

Or, it's Lucas.

[enigmas]

I'm not sure I learned anything from that Warwick apart from my P5 having entered the 'Twilght Zone' of Lucas electrics.

Yes, it doesn't make sense but P5 reality can be stranger than fiction

I'll recheck all connections again this weekend.

[dorsetflyer]

Vince, have you connected up like for like, normally the symptons you give are for a blown bulb or something similar, including a duff earth somewhere.
The call-out of the tags you quote are:-
P = W/Lamp
X = Supply
L = Indicator Switch.

49 = Supply
31 = Earth
49a = Indicator Switch.

If you look at these you will see that you have no connection to the warning lamp. (could that be the answer ?)

[enigmas]

John you could be right there. Another 'flasher can' I have is marked P, L, B.
I imagine that the B is Battery/Supply (+).

I have from your explanation transposed 31 for P (W/Lamp). Since both units have 3 terminals each, I assumed that they had the same function but were just given 'new' designations. I'll check it out this weekend. The 'old can' mustn't have fed an earth to the circuit.

The indicator lights on the dash do flash but they both appear to flash together on a left or right turn and have to the best my knowledge, always worked like this since I've owned the vehicle.

When I checked the manual, the 'flasher can' is positioned behind the dash panel at the top on a Mk 3. I believe mine may have been moved to its present location within the gauge pod?

[dorsetflyer]

Vince, you are right about 'B' being the supply, it's the same as 'X'.
However I don't recommend transposing 'P' with '31' as 31 is an earth lead.
I would suspect that your 'earth' contact would be in the can itself where there are only two tags on the unit. Originally they were fitted in a spring clip attached to a bracket at the top of the dashboard behind the binnacle. Easy to get out not quite so easy to re-fit.
Looking at the Wiring diagram the supply is also tied in with the 'voltage regulator' so any wrong connection can destroy it. So check that your fuel gauge is working OK.
On my 3.5 saloon I had problems getting the right unit and I found the one I fitted worked with the best flashing sequence when both warning lights lit up no matter which way the indicator was positioned.
Over the the length of time this 'forum' has been running and on the previous one, flashing indicators were a regular feature with all sorts of problems coming up, although it should by rights be simpler on the 3 litre as there is not repeaters (x4) to add into the mix.

[Phil Nottingham]

3 Litre and V8 indicator wiring is standard and if its not working then either the flasher unit or more likely its wiring is at fault. Corrosion of erathing points and lamp bodies is the most common but the numerous bullet connectors get full of dirt/rust and now even the actual cabling will be past on a 3 Litre and many early V8's.

Systematic checking of all circuits is only way to resolve this - mechanical units of both types are redaily available and modern electronics will fit with wiring mods (Use SEARCH)

Its also a good opportunity to fit a hazard switch and flasher unit

PS meant also to add that the "metal" lamp bodies both front a rear lamps provide the earth return to the bulb and then also by a separate wire in addition to the screws fixing to the (rusty) metal wings. This metal ceases to be conductive as it ages and can look Ok. The rear lamps being low wattage will work OK but brake and flasher will be too much. Putting on brakes and indicators at the same time often leads to more than one other lamp flashing (this fault is common on many newer cars too). dead givaway of bad earthing/corrosion. often it will just not work A Dremel may be used to clean out the inside of the bulb holder if not one too far - protect with Vaseline. In the long term new units will be needed beware s/h though

Depending on the flasher type the bulbs will either flash too quickly (old 3 pin) ot too slowly not all (2 pin) Electronics can do any combibation or no effect other than the warning light (if correctly fitted)

[enigmas]

Continuing on with my indicator/flasher can saga. I did a bit of research and have adapted the wiring circuit for my coupe. Interestingly my old and apparently failed can now works on the test circuit, so I'll be scrutinising the original wiring? and wiring up the alternative circuit to work with current technology flasher units.



WIRING KEY

GW Green/White

LGN Light Green/Brown

LGP Light Green/ Purple

GR Green/Red

FLASHER CAN TERMINAL DESIGNATIONS
(Old & Current. For Negative Earth cars)

P or 31 to: W/Lamp (Also an Earth (-) )

X or 49+ or B to: Power (+)

L or 49a to: Indicator Switch


NOTE:
Early style ‘metal cans earth through their case, so were mounted to the frame.
Current plastic cans require a separate earth or negative feed.
This may account for some of the indicator problems and erratic operation experienced by these cars (for years), as changing from a metal to a plastic body canister (at some point in the car’s history) and not providing an alternate earth feed would cause weird electrical paths.

[Phil Nottingham]

the 2 terminal mechanical flasher cans do not require an earth - these were fitteed to later P5b's.
the warning lights with these are just in parralel to the side indicator that is on and and earthed direct.

This is the best way to go as these these are cheap and easy to get and very relaible. The redundant P warning light lead is earthed and the dash warning lights swapped left to right and vv.

Vehicle Wiring Products do all types anyway.

All this has been covered before too!

The drawings are helpful though

[enigmas]

Phil I tried to find 'indicator/flasher can' info using search on this board but found little of relevance. Can you provide a link to this info. Thanks ~ Vince

[Phil Nottingham]

roverp5.proboards31.com/index.cgi?action=display&board=Rover33&thread=2345&page=1

did you set days search to 2000 and number of posts 100?

Try also warning light,

[enigmas]

Thanks Phil.

[enigmas]

Final Note:
I spent most of today (Sunday) removing the dash panel and cleaning all the connections to the dash switches. Quite a few had an oxide coating (green)? After I'd finished I noticed a substantial improvement in the operation of the switches especially the wiper switch which was seemingly developing a delay (bad connection causing resistance). It's probably been close to 10 years or more since I removed the dash ...so I really can't complain.

As an aside all my head light switches run through fused relays so they don't have to deal with the heavy current draw caused by the quartz halogen headlights fitted to my car.

Indicator Circuit:
I ended using the circuit with the supplementary earth as this worked very well and all I needed to do was to add one wire to ground. This provides a very clean and direct earth path and has solved my indicator problems.

[Phil Nottingham]

Its surprising how much corrosion can form on switch contacts, bullets and Lucars. I have long converted to relays for the main headlamp switch fater having lost all lights in the middle of the night in the N Wales hills travelling back from Ireland once. The switch overheated - as many P5 owners raely travel at night they never realise that the terminals corrode and cause high resitance which overheats the switch when the lights are used . It only needs it to happen once and the switch is ruined as may the cables to it specially if they are the later PVC. Past overheating is usually obvious from the metled Lucar insulation covers

[Warwick]

Phil, don't forget those immortal words of Joseph Lucas ... "A gentleman does not motor about after dark."

[enigmas]

Right on Phil. Once you start upgrading the headlights to modern lighting standards the switch is unable to deal with the current passing through it and usually ends up cooked. Adding relays to carry the heavy current makes all the difference and preserves the switches. The driving lights on my car (actually aircraft landing lights) also operate through relays.

(* I have no idea why Rover didn't/wouldn't include a 'direct' earth feed into the indicator circuit?)

[Deleted]

I always thought that quotation was from Rolls Royce salesmen when they used aceytelene lamps as an optional extra and the only electrics was a magneto for the spark.
In the US, Lucas is often referred to as the Prince of Darkness.

[enigmas]

Also in Australia.