Electronic Flasher Unit

[Mike Collins]

I'll have a look tomorrow for the part number of the flasher relay.

 

Bill,

 

The part you have linked to, 90 494 187, is a wiper delay relay, according to Vauxhall parts list.

 

The flasher relays should be 92 854 85 or 91 482 92

 

If you find a 90 506 697 it's used with extra lamps on a trailer.

 

That delay relay could be useful, one day I plan to try to fit one I have to mine.

 

I don't know if there's much similarity between a TR indicator switch and the Spitfire arrangement but years ago we had continuous ticking from the indicator relay. It turned out to be metallic particles in the switch itself. I think they came from the horn slipring.

 

Mike.

[badshead]

Thanks Mike - will help with my search.

[badshead]

I think I know why the electronic unit ticks.

 

Electromechanical flashers don't do anything until the column switch is closed in either direction when it will then pass current through the bulbs. If the electronic unit is connected in place of the standard flasher it has to permanently operate, because it doesn't rely on the current through the lamps for its operation, but you only see the flashing when the column switch is closed. However, if this flasher has a relay in it, the relay will be continually making and breaking the connection so it makes a clicking noise all the time. The only way to prevent the electronic units ticking is to buy one that does not use relays.

 

Tony

I've been thinking about this... the electronic unit is permanently live so, as you say, it's effectively 'relaying' constantly, but will send current to the lamps when the indicator switch is closed. The only solution therefore must be to use the switch to energise the unit as well as close the circuit to one set of lights.

 

Another thought.... as the electronic unit uses an earth connection, if I simply joined the earth terminal the load side, operating the indicator switch would provide a route to earth and prevent the relay from operating at other times (or would something go up in smoke)?

[tthomson]

Tony

I've been thinking about this... the electronic unit is permanently live so, as you say, it's effectively 'relaying' constantly, but will send current to the lamps when the indicator switch is closed. The only solution therefore must be to use the switch to energise the unit as well as close the circuit to one set of lights.

 

Another thought.... as the electronic unit uses an earth connection, if I simply joined the earth terminal the load side, operating the indicator switch would provide a route to earth and prevent the relay from operating at other times (or would something go up in smoke)?

 

Hi Bill,

 

Sorry, I had to go out last night.

 

Your thinking is absolutely correct for electromechanical devices, but totally wrong for electronic devices.

 

With electromechanical devices, what you connect where is often unimportant and generally the unit will survive. Electronic devices do not work in the same way. The earth wire is only passing a small amount of current so if you put the bulbs in the earth circuit, they will not light up, but the unit will carry on ticking when you connect the lights, because the lights will offer a very low resistance path to ground so will be invisible to the unit.

 

To get rid of the ticking you would need the indicator switch to provide the power to the flasher, but then you would need a flasher for each side . It starts to get complicated. I'll give it some thought and get back to you

 

Tony

[badshead]

It starts to get complicated. I'll give it some thought and get back to you

 

Tony

Yes I agree, just bugs me that it works perfectly OK in my Stag (and other TR6s apparently), but not my TR6. I'm going to replicate the indicator circuit on the bench with the electronic unit to see what happens.

[TonyMerrygold]

Fascinating topic. I don't have this problem on either my TR4A or TR6 but I do on my E-Type.

 

The electro-mechanical flasher was replaced with an electronic one and when the engine runs it ticks as described.

 

If the ignition is turned on but not running it doesn't tick. It ticks in synch with the fuel pump so is obviously picking some sort of signal up from the pump, presumably via the earth connection.

 

When I get a chance I'll disconnect the earth on the flasher as described and see if it has any effect.

 

If not then I am keen to replace the flasher unit with one that doesn't do this.

[badshead]

Tony

 

I've never completely solved this, but cleaning the contacts on the indicator switch did make a big improvement. I still experience occasional clicking from the flasher unit when the indicators are not activated, but only when the car has not been used for a while and even then only in the first few minutes after starting - weird!

[tthomson]

Tony

 

I've never completely solved this, but cleaning the contacts on the indicator switch did make a big improvement. I still experience occasional clicking from the flasher unit when the indicators are not activated, but only when the car has not been used for a while and even then only in the first few minutes after starting - weird!

 

 

 

Hi Bill,

 

Electromechanical flashers work with high current draw. When an electronic one is designed the designers will anticipate that the indicator switch is designed for a heavy current flow so the replacement flasher is designed to replicate a smaller but still significant current flow. The thinking is that the indicator switch uses the high current to limit corrosion of the contacts by "burning off" any ****, so a replacement one should continue to do this. By cleaning the contacts, you have removed any resistance from built up **** and this may have made a significant difference. The start up ticking may be due to the electronics coming up to normal operational temperature. Difficult to know without being there, but it might explain why the stag works without ticking!

 

Whatever your doing if it gives you the desired result then it seems like it is the right thing to do.

 

TT

[tthomson]

Fascinating topic. I don't have this problem on either my TR4A or TR6 but I do on my E-Type.

 

The electro-mechanical flasher was replaced with an electronic one and when the engine runs it ticks as described.

 

If the ignition is turned on but not running it doesn't tick. It ticks in synch with the fuel pump so is obviously picking some sort of signal up from the pump, presumably via the earth connection.

 

When I get a chance I'll disconnect the earth on the flasher as described and see if it has any effect.

 

If not then I am keen to replace the flasher unit with one that doesn't do this.

 

 

 

Hi Tony,

 

I would be surprised if the flasher unit is synched with any other component; probably has a very similar flash rate as the fuel pump by coincidence, but you never know. Sometimes I am flabbergasted by the ingenuity of electrical systems.

 

I have mixed feelings about using electronic flashers (even though I have designed the one I am using). If you are using incandescent bulbs, then electromechanical ones offer some advantages. If a bulb is dead, the flasher runs fast. If you are looking to replace the incandescent bulbs with LEDs then the current flow will be too small for the flasher and it will either not flash at all, or it will run fast. Similarly if you mix and match LED and incandescent. In these situations, the electronic ones which do not rely on current flow will work better, but as you have discovered some tick. This is because to have a load independent flash rate, the electronics use a timer chip and relays. These run all the time and what you can hear is the relay clicking on and off. Some relays are quieter than others so some units won't appear to tick.

 

Some really clever electronic flashers are able to sense the attached load and will also not tick, but they expect the current to be typical of incandescent bulbs.

 

To have full electronic flashing without ticking, the circuit needs a serious change and this requires modifications to the loom. (This is the approach I have taken in my car).

 

TT