Wonky Flashers

[JeffR]

For some time now I've had a problem with the speed of the flashers on my 4 when the engine is idling (like at a junction). They very quickly become very slow or stop altogether. When the engine revs increase the flash returns to a normal rate.

In an attempt to address this I've just retrofitted my flasher system to LEDs using an electronic flasher unit, all purchased from Classic Car Lighting and as used on my TR3 which work fine.

I now have a similar problem with the newly installed LEDS on my 4 as I've described above for the normal bulbs. Very slow and dim flashes at idle speed which revert to normal as soon as the engine revs pick up.

I've checked the voltage across the car battery at rest when not under load or charge. It is 12.7v. Voltage between the live pole (-ve) and earth on the car body is also 12.7v suggesting no earthing issues.

With the ignition on and flashers turned on while the the engine is off the voltage between the live pole and earth is 12.3v - giving a slow and dim flash. The emergency warning lights do not fire at all until the engine is on and charging - which is clearly an issue!

With the engine started the flashers suddenly become come much brighter and alive - this happens as soon as the red ignition warning light goes off and the revs increase - which is at about 1,000rpm. A factor which may be relevant is that after installing a new (repro) dynamo a few years ago the red ignition warning light stays on longer until the revs are higher than with my original Lucas dynamo.

I've experienced a similar problem using a brand new battery. Initially the flashers flash at a normal speed but then after some mileage the same slow flashing problem occurs using the new battery? This leads me to suspect the dynamo may not be charging at the correct voltage - albeit the battery is fully charged and starts the engine fine.

Any thoughts or solutions to this problem are appreciated.

JeffR

[stuart]

Definitely sounds like it could be dynamo, have you checked its output by checking with a bridge wire across the two terminals. Short bit of wire with the strands exposed in the middle and measure with a meter at the exposed centre with one probe and earth the other probe to the casing with it just ticking over and then see what happens a you bring the revs up.

Stuart.

Edited April 4 by stuart

[RobH]

It sounds as though you do have a connection problem somewhere Jeff . 

Using a meter without any load on the system can give a false reading because the meter draws next to no current. That means a poor connection will not 'drop' any voltage and the meter reading looks good.  If you want to do a meaningful reading , turn the sidelights on so that some current is being drawn.  Your second test was  more meaningful, the 12.3V reading is the true one and the voltage is probably being lost in a bad connection somewhere. 

Also be aware that meters can lie.  Can you try another to confirm your readings? 

A fully charged battery should read about  12.7 - 12.8V so that is OK for the battery itself off-load which suggests the dynamo is charging it OK.

The oddity is that you say starting is no problem as that suggests the connections are good. Where was this 'live pole' - do you mean the battery terminal ?  

I would start by thoroughly cleaning the battery clamp connections and the connections at the other ends too - to the body and the solenoid. Make sure there is bright metal-to-metal contact on all of them. 

 

 

Edited April 4 by RobH

[Lebro]

What flasher unit are you using ?

Bob

[JeffR]

Thank you all for your replies. A few things to follow up on there - I'll report back.

Bob, the flasher unit is the Classic Car Lighting positive earth electronic pot shaped one with the wire coming out of the centre - albeit I have the same results using my original steam powered flasher unit using original bulbs.

I don't think it is the battery as a brand new battery - whilst working OK re: the flasher when first fitted soon settles down to the same old problem after its been on the car and driven for a day or two - suggesting it is the charging circuit. I'll also take the advice given about cleaning the connections to the battery and do both ends of the lead.

Cheers,

JEFFR

Edited April 4 by JeffR
clarity

[Lebro]

Ok, sounds good, unless it has become faulty. Can you measure the volts between earth, & the "X" terminal on the flasher unit with ignition on, engine not running. That may give you a clue.

Bob

[RobH]

31 minutes ago, JeffR said:

soon settles down to the same old problem after its been on the car and driven for a day or two - suggesting it is the charging circuit.

If the battery wasn't getting charged properly, the off-load voltage on it would be low and you would have difficulty starting the car. 

Battery voltage is directly related to the state of charge through cell chemistry, so unless your meter is telling porkies, 12.7V should mean it is fully charged. 

You said this problem happened with both the original and replacement flasher units so that should eliminate those, though of course, not the connections and earths to the lamp units. 

Edited April 4 by RobH

[Lebro]

You have earthed the flying lead from the flasher unit haven't you ?

Bob

[JeffR]

Bob, yes, the flying lead is earthed. This lazy flashing also ocurred using the original flasher and normal bulbs

One other consideration is that the replacement dynamo I fitted was brand new from one of the usuals. I had requested a positive earth unit but after fitting it and starting the car, I noticed it was tagged negative earth. I had noticed on first starting the car that the ignition warning light stayed on for a few seconds longer than normal before it extinguished . As the dynamo was by then showing a health charge on the ammeter I assumed that the dynamo had self polarized? Could that be part of the problem. Is it worth re polarizing it using the usual method?

JEFFR

[RobH]

No - re-polarising won't change anything if it's already working and ';producing a healthy charge'.  

This fault doesn't sound to be anything to do with the dynamo if it is charging OK.  When the ignition light is on, the cut-out contact in the regulator is open and the dynamo output isn't connected. That is to prevent the battery driving it like a motor when the dynamo output is too low.  

Your problem seems to be that the battery alone cannot drive the flashers - which it should be capable of doing quite easily.  If the battery really does have full charge, the only thing causing this must be a bad connection.

[Lebro]

At risk of repeating myself !!

Can you measure the volts between earth, & the "X" terminal on the flasher unit with ignition on, engine not running. That may give you a clue.

if you a good 12V (or very close) at "X" (while trying to indicate one way or the other) that eliminates any bad connection up to that point. after that it is the run from "L" on the flasher unit to the indicator switch. beyond that there are two separate circuits - left & right. they won't both be faulty.

Bob

Edited April 4 by Lebro

[JeffR]

Hello All,

To update you on the tests I've done so far;

Dynamo output (as suggested by Stuart). Connecting a wire between the D and F terminals on the dynamo and running the car at 1,000 rpm gives a reading of 14.5 - 15v.

Measuring the voltage across the battery terminals when the engine is running produces a reading of 13.25 - 13.5v.

Next step is to check the voltage from the X terminal on the flasher unit.

I'll also try reinstalling the new battery to see if it makes any difference.

Thank you all for your assistance so far.

JEFFR

[JeffR]

Hello All,

To update you on the tests I've done so far;

Dynamo output (as suggested by Stuart). Connecting a wire between the D and F terminals on the dynamo and running the car at 1,000 rpm gives a reading of 14.5 - 15v.

Measuring the voltage across the battery terminals when the engine is running produces a reading of 13.25 - 13.5v.

Next step is to check the voltage from the X terminal on the flasher unit.

I'll also try reinstalling the new battery to see if it makes any difference.

Thank you all for your assistance so far.

JEFFR

[JeffR]

Voltage on the X 8v. Problem solved - dirty fuse contacts!

Thanks all for your assistance.

JEFFR