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MG MGB Technical - Slow turn signals

My turn signals sometimes run very slow between flashes. Particularly the left side. I have done some work on the electrical system by adding a third brake lite over the liscense plate and I have connected daytime running headlites to go on when the key is on. I have put in a separate switch so I can use it when I want. When used the signals run slowly or bearly run at all. This occurres at idle (800RPM) only. In normal driving they work OK. I thought alternators output was not effected by engine speed. Am I wrong? If I do not use the daytime running lites the signals do run better. I like the safty they provide! Thanks Bob
Bob Ekstrand

I may be corrected on this, but I know on may car that when the turn signals flashed slow it was due to a lack of and/or bad grounds. After I cleaned and added some additional grounds my signals work great now.

Robert
Robert Browning

The flasher unit works by heating up a strip of aluminium which operates a bi-metalic spring contact. The heating effect is of course related to the current being passed. This is affected by; total bulb wattage; available current (battery condition and generator output); circuit resistence (poor contacts and earths); the quality of the flasher unit (very variable!!). Therefore check the wattage of the bulbs (21Watt), clean or replace all the spade and bullet connectors and put good earths to each light unit.
AL
Allan Reeling

Replace the flasher unit with a 3 pin electronic unit available from any accessory shop. make sure you buy one with pins numbered '49', '49A' & '31'.

Connect the live from the indicator switch (light green with brown trace) to '49A', connect the live to indicators (plain green wire) to '49' and run a separate earth lead from a suitable point (I used the wiper motor mounting) to '31'. By bending the original bracket slightly you'll be able to fix the new unit to the same point under the dash.

The original thermal units are very sensitive to voltage variations, modern electronic units will regularly even if the voltage is a little low.
Mike

Mike,

On my 77 US spec roadster, the flashers flash normally AFTER they start. But, they take 1 or 2 seconds to start flashing after I hit the signal lever.

Is your suggestion good for my car and problem also?

Thanks,
Charley
C R Huff

I had this exact problem .....primarily on the left side...... and just managed to fix it last week on my 73B roadster.

Over 6 months of driving I checked grounds, replaced wires, hazard switch and turn signal flasher plus did a great deal of testing including pulling the front bulb housing with no cure.

The problem turned out to be the bulb in the front left. I should have gone around and replaced all 4 bulbs as the first test. Since all of them lit up properly though who would have thought????

Finally last weekend I switched the front and rear bulbs left to right. The problem switched sides with the bulbs. The front left bulb (double element) seemed to be fine but there must have been some sort of bad internal connection or high internal resistance because as soon as I put in a new bulb the signal lights finally worked correctly again. A week later and I still can't believe how great they are working again.

BH
BH Davis

check the output at the battery, it sounds like low altenator output, let us know. RIC
RIC LLOYD

Bob - Check the voltage at the battery while the engine is idling and again when it is reved up far enough that the turn signals are operating at the speed that they should. I think that you will find that the alternator is dropping very low at 800 rpm. If so, you might want to take it into a good auto electric shop (not one of the big box auto parts stores with a alternator checker on the back counter) and have it checked. the alternator may be marginal or it may be as simple of just needing a smaller pulley on it. Cheers - Dave
David DuBois

It's worth searching around for any press connectors that have been put into the wireing for towing.
As a last resort you can replace the rear bulb with a combined stop tail lamp bulb, and solder across the bulb terminal.
c cummins

Good grounds did the trick for me...
Pete

This thread was discussed between 18/06/2009 and 19/06/2009

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