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MGA Troubleshooting the turn interuptor circuit.. MGA

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ronzet

ronzet

Jedi Knight
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Good day all you fellow fanatic LBC nuts.. /bcforum/images/%%GRAEMLIN_URL%%/smile.gif

I finally got <u>most</u> of my electrical rebuild finished on my frame off '57 A. I have a Moss harness that is of very good quality, by the way.

This is a quick sitrep.

The iginition circuit, as far as I have installed it, appears to work with the prime indicator being the fuel pump coming on when the ignition is turned on as well as the instrument lights coming on. The healdlights, dash, and brake light all work.

The parking and tail lights do not. There are three components, or combination thereof, in the circuit that could be the culprit, The flasher unit, the flasher relay, and the turn signal switch. The flasher unit (the firewall mounted cylindical unit) is new so is less than suspect. The flasher relay and turn signal switch are originals.

Rather than spending the $300+ to buy both the flasher relay and turn signal switch, I am seeking a bit of advice.

Sooo, the query.

Can anyone suggest a troubleshooting technique that will help me determine which part, if any, is at fault, if there is a tiny little wire somewhere in the bundle that I have forgotten to connect, or ????

Any advice appreciated... I am all ears.. /bcforum/images/%%GRAEMLIN_URL%%/rolleyes.gif
 
Ron - What about the brake lights, do they work? Both the parking lights and tail/brake light bulbs should be dual filiment units. The low wattage filiment of each bulb serves as parking and tail light, while the high wattage filiment doing the job of turn signal and brake light. If you have no parking/light light AND no brake or turn signal light, I would start looking for a ground issue at both ends of the car first. The only part of the turn signal circuit that will affect things is the relay and it only powers the high power filiment of the parking light and the brake/turn light at the rear. I am sending you a wirng diagram for a late TD with the turn signal circuit high lighted. The circuit in your MGA should be exactly the same.
Cheers,
 
David,

Thanks for your suggestions and the diagram.

The brake light DO work... I have paid particular attention to the grounding of all of the circuit, breaking my trusty old multimeter out to check for continuity front and back.

I guess the real delimma is in the fact that I do not have a schematic of the inside of the 'black boxes' and can therefore not ascertain the actual workings. I was going to bypass the turn switch but not sure if the circuit is open (ground) or closed (hot) as it feeds the relay unit...This is a particular problem as I try to troublehoot the Relay box as it feeds the lighting circuit.

As we speak I have thought that I should check the license plate circuit to see it it is hot. I do not have it connected up to a light yet and it is probably a second test point in addition to the brake lights....

I am begining to think that there is a fault in the relay unit...either internally or in a power feed. I have double and triple checked the wiring and it appears to be correct.
 
Kimberly,

Yes the 'black boxes' are clearly numbered and wired correctly per the color coded wiring diagram. /bcforum/images/%%GRAEMLIN_URL%%/grin.gif

I am using the term 'black box' to indicate that I do not know what is actually going on inside.

In other words, I can surmize the function of each pin based upon the 'from where and to what' wire that is going into or out of the box, You know, this wire feeds the relay coil, this one is a closed/open relay point, etc...I would just feel better with an internal schematic... /bcforum/images/%%GRAEMLIN_URL%%/smile.gif

Perhaps I am just being anal about it... /bcforum/images/%%GRAEMLIN_URL%%/wink.gif

/bcforum/images/%%GRAEMLIN_URL%%/cheers.gif
 
Good news...

I found a schematic diagram for the flasher unit in an old MGA shop manual.... will advise my progress,,

Thanks for the input and suggestions... /bcforum/images/%%GRAEMLIN_URL%%/thumbsup.gif
 
IMO, NO amount of checking/DoubleChecking continuity & grounds is anywhere near anal where Lucas electrics is concerned, Ron!!! LONG external leads and a VOM are prerequisite for the task, and ONE wire at a time, isolated from any control gizmos if you've got "issues". You're on it proper. Keep up the good work! /bcforum/images/%%GRAEMLIN_URL%%/wink.gif
 
Oh 'Great Pumpkin'... /bcforum/images/%%GRAEMLIN_URL%%/bow.gif

Thank you for these words of encouragement for a lowly Jedi Warrior from so sagely a guru.... /bcforum/images/%%GRAEMLIN_URL%%/smile.gif

Sending this to you, in secret on pain of death, from the realm of Lucas, Prince of Darkness... /bcforum/images/%%GRAEMLIN_URL%%/wink.gif

I will continue this quest, tho others may fail, we will prevail....or die trying /bcforum/images/%%GRAEMLIN_URL%%/yesnod.gif
 
Re: Troubleshooting the turn interuptor circuit..

Bit heavy on both flattery and... err... peggin' th' (analog) BS meter, Ron. /bcforum/images/%%GRAEMLIN_URL%%/smirk.gif

Just don't let th' smoke outta that new harness! /bcforum/images/%%GRAEMLIN_URL%%/devilgrin.gif
 
Re: Troubleshooting the turn interuptor circuit..

/bcforum/images/%%GRAEMLIN_URL%%/lol.gif

When in doubt.. tongue in cheek whenever you can... /bcforum/images/%%GRAEMLIN_URL%%/thumbsup.gif
 
Re: Troubleshooting the turn interuptor circuit..

DrEntropy, One question... where in the world is Elsinore <u>DK</u>????
 
Re: Troubleshooting the turn interuptor circuit..

PM in your frame.
 
Re: Troubleshooting the turn interuptor circuit..

DrEntropy,

If we are talking about Denmark... I love that country... been there. Many years ago... Stayed in the Admiral Hotel on the waterfront... I should be so lucky... and, if so, you are up far too late into the wee hours... /bcforum/images/%%GRAEMLIN_URL%%/rolleyes.gif

If not... there are many places that are PM to me... /bcforum/images/%%GRAEMLIN_URL%%/smile.gif
 
Re: Troubleshooting the turn interuptor circuit..

Ummm... I'm a humble photojournalist by trade, nature and training. Had to wrench on my own cars from 1969 in order to own and drive 'em. It's a long, sad tale not worth th' tellin' as to how I wound up using the hard-won knowledge from those times to these to put beans onna board. Now it's I.T. contract for small businesses wot can't afford 'in-house'.

...as I said: long, sad tale. /bcforum/images/%%GRAEMLIN_URL%%/devilgrin.gif /bcforum/images/%%GRAEMLIN_URL%%/jester.gif
 
Re: Troubleshooting the turn interuptor circuit..

should I break out the fiddle to help the tale go by more smoothly? /bcforum/images/%%GRAEMLIN_URL%%/jester.gif
 
Re: Troubleshooting the turn interuptor circuit..

Ron - Did I send you the wiring diagram last night? I can't remember that far back, but I don't think that I did. If I did, the wiring diagram has a drawing of the relay on it and you can use that to check the relay in your car. I would start by removing the cover, turning on the ignition, then working the turn signal switch in each direction while watching the relay to see if it moves. If it doesn't move, check that you are getting voltage to the terminal for the coil. If the voltage is to the coil, check that the relay is grounded properly. The two relay coils are grounded through the coil. If the relay is moving when power is applied, try cleaning the contacts and check with your trusty meter to see that they are making contact. If the relay is bad, let me know, I can make you a replacement for a heck of a lot less than the one from Moss or V/B cost.
 
Re: Troubleshooting the turn interuptor circuit..

DrEntropy,

'Tis a sad tale to be true... /bcforum/images/%%GRAEMLIN_URL%%/smirk.gif

You said IT??? as in Information Technology??? If so, visit this site https://www.as400search.com . It will 'splain everything... One of the company owners goes by the alias 'ronzet' in some circles.
 
Re: Troubleshooting the turn interuptor circuit..

David,

I never received the wiring diagram. If you could be so kind.... /bcforum/images/%%GRAEMLIN_URL%%/thankyousign.gif
 
Re: Troubleshooting the turn interuptor circuit..

Gentlemen,

I just found a website that is an unbeleivable source of everything you ever wanted to know about the MGA... circuit diagrams, wiring harness routing, oil systems, engine rebuilding, bodywork, ad infinitum.

It is:

https://mgaguru.com/mgtech/index.htm

check it out... /bcforum/images/%%GRAEMLIN_URL%%/thumbsup.gif
 
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