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MG MGB GT V8 Factory Originals Technical - WIRING HELP!??
I have been out in the garage buttoning up wiring on the V8 and running into problems. I paid close attention to the distributor/coil wiring, but failed to scrutinize the Starter wiring.
I have the heavy Batt cable hooked up fine, but I now have 3 sets of brown wires with eye terminals one them and one or two of them put a drain on the battery (like full 12V!) The other cable goes up to the Alt as verified by checking continuity. Where do the other ones go? I am at a loss and to not wish to melt the wiring harness down..
|The three browns go to the same stud on the solenoid as the main cable from the battery, however you must find out where the drain(s) are coming from first. Connect each brown in turn to the battery via a test-lamp. |
If the test-lamp glows brightly you have a major drain and should not connect that wire direct to the battery until you have found where it is coming from and removed it or you could cook the wiring.
If the test-lamp only glows dimly you are unlikely to cause problems by connecting that wire direct to the battery, but still need to find out where the drain is coming from.
If the alt is showing the drain it has one or more diodes failed short-circuit, but make sure you have the battery connected the right way round first.
Obviously make sure everything on the car is switched off or disabled first including courtesy and boot/trunk lights.
|Well, glad to see my memory was intact. |
I thought they all went to the same post on the starter. I added a bit to my website outlining the problem I am having along with a wiring diagram of the Unilite Distrib. It is on my website at: http://www.embreyfamily.com/mgb/TechRoom/MYMGB302Conversion/Jan2002.htm
So one of the browns is Alt, I know that one is not connected and is protected from shorting (and thus it is not drawing current) but where do the other 2 lines go to? Let me know so I can try and trace the short.. I put a volt meter on the 2 browns and they draw full 12V, so something is drawing on them good.
More info. At this point none of the wires for the Coil, Alt, Distrib are connected to anything, That is one reason I was hooking wiring back up, my New Unilite distrib does not use the same wiring format as the old MG distrib set-up, so I am a bit lost as to how to hook it all up.
If anyone can review my outline on the website and get back to me either here or via email I would greatly appreciate it!
|Well after much cross checking, continuity and voltage testing I have all 3 of those wires hooked up to the starter and the battery connect as well. I "THINK" the 6V draw I am seeing could be from my radio which is a modern unit with memory etc, and probably the stock clock also..|
Once all was connected I checked all the lights, the wipers, hazards and all worked. I turned the ignition on and was greated by the pleasing sound of the starter relay clicking into readyness. Then rechecked all lights etc, radio turned on. Moment of truth I tripped the starter AND SHE WORKED! I am still a bit confised as I have the Wht/LtGrn wire just hanging, the wiring diagram shows this going to the distrib/coil, what should I do?
|OK, I now have the Alt connected up. The wires I have left are as follows (wire color from stock loom)|
Wht/Blk - shows Constant ground
Wht/Red (noted as white+ballast from dissasambly) - Ignition activated ground
White - Ignition active pos (+)
Wht/Grn - Ignition activated pos (+)
I called Mallory tech support and they said all Mallory Unilites wire up the same, but I am now seing 2 different wirings in regards to the ballast, one has theCoil and Distrib after the ballast, the other has only the coil after the ballast. Any ideas? I am thinking of hooking up all after the ballast and seeing what happens, figuring better to have the ballast resistance than not, worst case it does not work and I switch it out..?
|All is solved!|
I was able to test, connect, test, connect and test some more until it worked. Here is how the Unilite connected to my system.
This follows the Basic Unilite connecing diagram on my website and stock MGB wiring colors.
car wire -> connects to -> then pass to
Wht/Grn -> Ballast -> Coil(+)
Coil(-) -> Distributor Grn
White -> Distributor Red(+)
Wht/Red -> Distributor Brn (GRND)
I chose to use the Wht/Red as my ground rather than the Wht/Blk. Thwe Wht/Blk is constant ground, while the Wht/Red is ignition swith activated ground. My reasoning is that it add a failsafe to turning the ignition off should the (+) side get frozen or stuck on.
|If by '12v draw' and '6v draw' you mean that is voltage displayed when a voltmeter is connected inplace of the battery ground strap then 6v is a microscopic current e.g. the normal leakage current for alternator diodes and possibly for radio memory too. 12v could be anything from a few milliamps to a full short, the test-lamp will indicate which.|
|Paul, Thanks for the response, it is all sorted out now. I have a modern radio with memory and it is the main draw. It sat overnight hooked up and the battery still had juice to turn thr car over, which is good considerig the battery has sat for a year now without being charged..|
This thread was discussed between 26/01/2002 and 27/01/2002
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