MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - electrical guru help needed

Good morning Gent's

I am a bit confused here. Lets me explain , a total resto was undertaken. Incl new wiring etc. All grounds are perfect. All light's work as it should .
EXCEPT the right direction lamps. Checked the wiring diagram over and over with my glasses on . No faults to be found . Have changed the flasher twice to no reveal. Changed the relay box also to no reveal.

Noticed when I switched the direction light switch to the left the dash indicator lamp came on as it should . When turned to the right nothing . I fumbled a bit with indicator bulb and bingo the right indicator lights came on also the dash indicator works.

What I don't understand now is the following is there some kind of return via the dash indicator bulb ???.

Car is negative ground and checks were performed with a batt -charger set at 6 volts 3 amp.

Your guy's wisdom here is much appreciated,

Gerard

Gerard Hengeveld

Gerard, first thing is - Our cars are 12 volt systems, not 6 volts.
There are some bulb sockets in which the bulb can be plugged in in either of two orientations. You may have one of these in your right lamp housing. These sockets use bulbs where the two small metal pins on the side of the bulb are not staggered. Check the bulb in your right lamp housing. If you can do it, pull the bulb out, rotate it 180° and reinstall it. See if that changes things. Bud
Bud Krueger

Bud I have done that also ( turning / orientation bulbs in the housing ) . Sorry for the typo: 6 versus 12 volts . I started the wiring test with 6 volts and later switched to 12 volts no change .

Gerard
Gerard Hengeveld

Good morning Gerard,

I will take a shot at this problem. First, the old bimetallic flasher is a rather crude device. It depends on sufficient current flow to heat a bimetallic strip that due to the bimetal difference in expansion bends when heated and interrupts the circuit and in turn current flow. The strip cools and the strip returns to do it all over again. Accordingly to the wiring diagram in the WSM the relay coils if the turn signal relay are attached to the flasher. also of course are the filaments of the front and rear lamps and the dash indicator. When the resistance of these devices are connected in parallel the resistance decreases and the current through the flasher increases. the more current the faster the blink rate.
Since to relay coils are always in use they should always represent the same resistance as viewed from the flasher. If one side works and the other fails to blink there is probably a high resistance that is limiting the current that heats that bimetallic strip. Since you have all new grounds in good condition I would look at lamp sockets for a poor connection on the bad side.; Possibly also the dash indicator. If all look new and clean and mechanically sound go back and check those grounds (earths). Remember the whole signal system is crude by electronic standards. It will work with a wide variety minor faults but also fail for what seems insignificant reasons.

Regards,

Jim Haskins
J. M. Haskins

Dear Friend thanks for the comments and they are perfectly clear.But what I don't understand in the system is : If you take the dash indicator bulb out the left side ( turn signals ) work flawlessly and the right side don't. Now by putting the the bulb back in again both sides work perfect .

Further info : I switched the relay boxes from a overhauled one to one from from Moss no change in behaviour as discribed earlier. I feel like a dumbo.

All grounds and sockets are good .

Gerard
Gerard Hengeveld

Gerard.

Check and see if the light bulbs are the same wattage. That can happen if you have different bulbs from side to side.It will help if you open and clean all plug-in terminals using di-electric grease to seall them from moisture.I use a 22 cal cleaning brush.
Sandy
Hudson Fl
ss sanders

Gerard,
I had the same problem on the turn single switch I had the hot wire on one of the turn single posts. Switched it around and all worked fine.

Hope this helps,
Ed B.
E.P.B. Brennan

I think you may have a poor ground on the right side indicator so it is feeding to ground thru the left bulb in the circuit. This increases the resistance to 3 times that of one bulb, therefore less current and no flash if left bulb is out
Don Harmer

Problem FOUND !!!!!!!!!!!!!

Starting this morning early ( rare for me )at 0500 hrs . And went over everything again.
At the last I decided to check the dash lamp holder fitting . Took it out and started to measure resistance ...DUHHHH A minimal short was concluded in a brand new one ????? . Replaced it with another new one I had laying around and ....... Problem solved . It seems the culprit had a short in the resistance wire .

Thanks for all who helped me thinking,

Gerard
Gerard Hengeveld

This thread was discussed between 16/02/2014 and 17/02/2014

MG TD TF 1500 index

This thread is from the archives. Join this live forum now