Calling auto electricians

[KARL]

Although I have a basic understanding of circuitry, the following baffles me. The indicators and hazard lights are served by a single relay/flasher and there is a single flashing light on the dashboard for hazard lights and another/separate single light for the indicators. When the hazard lights are used everything functions normally but on the other hand in indicator mode (either/both sides) the lights flash too rapidly. On hazard lights the flashing rhythm is entirely normal so long as any two bulbs are in (front, rear, side to side – any two).

For indicator lights only: When the bulbs are taken out on one side the flasher clicks faster than normal when that side is selected (but with still more or less acceptable rapidity) and the dash light flashes in time with it (but of course no other light). Switching to the side with the bulbs in it produces flashes that are far too rapid (even faster than the no-bulb side) and the dash indicator does not come on at all. It does not matter which side this test is carried out on (absolutely identical result left or right) so, although I don't understand it, I assume the anomaly regarding the dash light is normal. If three bulbs are in then either/both indicator sides simply flash too rapidly although the one with both bulbs in goes faster than the other (same rhythm as before) and the dash indicator flashes for either/both sides.

In all cases bulb brightness appears to me to be good and normal. What is going on ? I would like to solve this myself with the right help rather than hand the vehicle over to a workshop for what must fundamentally be something requiring a minimum of effort (just the right knowledge). The vehicle is a Mark 1 Transit camper in otherwise very good condition. Any help, including a suggested forum for asking the question, would be most welcome.

[chas2008]

would of thought this would have been easy to sort out, cant get much more basic than a MK1 transit,no ECUs etc to worry about, many electrical problems on older vehicles usually end up with an earthing issue somewhere. Has it a towbar fitted ? towbar sockets can be a notorious area of electrical lighting problems, again especially on older vehicles..

[KARL]

Aha, never thought of that - yes, there is a towbar, must look into that. Many thanks, please watch this space in case I end up with a subsidiary/further question.

[chas2008]

the terminals get really rusty & cruddy on the tow bar socket as they are really susceptible to damp and the elements

[KARL]

Hold on - there is a towbar but no electrical connection/socket - back to the drawing board. Any suggestions ?

[chas2008]

corrosion on the terminals on the main fuse box ??

[KARL]

Thanks, the lights themselves are astonishingly clean and good looking - almost like brand new, yet I have gone over everything there as well as on the flasher. Must check the fuse box part although the way things work properly with two bulbs on hazard lights suggests it has nothing to do with the fuses (if it did then things would not work in any fashion, no ?).

[Hymie]

I’m not giving you the answer to your problem – but an explanation of how a basic indicator/flasher works – the rest you can deduce for your self.

The current to the indicator bulbs are fed via a bi-metalic strip, such that the normal current level results in the bi-metalic strip heating up. This causes the bi-metalic to bend (due to the different thermal expansion of the two metals used in the strip). The bending on the bi-metalic strip is so arranged to break the circuit to the indicator bulbs. With no current now flowing, the bi-metalic strip cools down and returns to its normal position, making contact and completing the circuit again. The whole process is then repeated again and again, resulting in the on/off sequence of the indicators.

This very simple arrangement has the advantage that should one of the bulbs in the indicator circuit blow, the circuit would draw ½ the normal current, causing the bi-metalic strip to only just break the circuit (due to the thermal mass of the strip), then having not heated so much, cool down quicker and re-make the circuit. When this happens, the flashers operate at approximately twice the normal rate (indicating that a bulb has blown) or possibly due to a poor earth in the system – resulting in a lower current draw.

[AlBags]

You sure you don't have a 6volt bulb in anywhere?

Also check earths between bulb holders and body.

[KARL]

Thanks for all answers - the problem turned out to be in the indicator switch (poor contact). I discovered this by trying all possible bulb combinations left, right, front, rear, both diagonals. It made no difference which bulbs were out/in so long as there were two in the circuit then the flasher behaved in hazard mode. When I went to indicator then there was a problem. Conclusion: the only new element is the indicator switch and very short wiring at it. Cleaned contacts on both sides, voila, problem solved.