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MG MGB Technical - Electrical Questions

1968 MGB:

I need your help in sorting out 2 electrical issues on my recently acquired MGB.

1) The PO has removed the control box from the engine bay and left the 4 wires disconnected. An alternator has replaced the original generator that probably came with the car. It is Lucas A1611 #23716-586. My research tells me that some alternators have a built-in voltage regulator and others a remote one that replaces the control box. Question: Is it o.k. to assume that I have the built-in voltage regulator and there is no need to reconnect the previous wires to an addtional control box?

2) I have the original electric type oil pressure gauge and pressure switch. The gauge behaves inconsistently. I have read the archives on how to do some testing. Question: My pressure switch has two terminals. A white/black (or brown)wire is connected to one terminal. Should there be another connection to the 2nd terminal? The only two dangling wires in the vicinity are a black one connected to a capacitor-shaped device mounted nearby and another white/black (or brown) wire that is not connected.

Thanks for your help in sorting this out for me.

Eddie
Eddie Haynes

Eddie,

As you have an electrical oil pressure sending unit on your car and probably, as it is commonly referred, a padded pillow dash, you never had a generator on your car. Your car always had an alternator but in 1968, when MG started using alternators, they regulator was remotely located on the inner right fender near the fuse box. Also, I am pretty sure that the regulator used with the generator cars had more than 4 wires going to them and the wires were all separate. The 4 wires going to the remote regulator for the alternator were, at one time, part of a single plug that kept them together.

I do not recognize the part number that you identified for the alternator that is on your car but I think it is pretty safe to say that some one has made some modification to the wire harness to by-pass the remote regulator and use the regulator internal to the current alternator. I suspect you would be having other battery problems if it were not connected properly.

As for your oil pressure switch, although there are two terminals on the switch, only one wire connects to the switch. The wire can be connected to either terminal as they are both electrically the same. I believe the white with black wire that you speak of should go to the switch on your brake block that is in the same vacinity of your fuse box and original regulator for your original alternator. I would like to suggest or for you to think about changing the oil pressure switch and gauge, as you become more comfortable and work on your car. The pre 1968 cars all had mechanical oil pressure gauges. The MGB went back to a mechanical oil pressure gauge around 1970. The gauge is the exact same shape as the one that you have in the middle of your dash, between the tach and speedo, and is much more reliable set up. If you can locate a car for parts, you can obtain all of the pieces that you need quite easily. However, I would NOT recommend that you put the hard line behind the dash as it would require you removing the dash. You can obtain an oil line kit from almost any auto parts store that would screw directly onto the fitting on the side of your engine and run it right into the back of your mechanical gauge.

HTH

Fred
Fred Wright

Eddie

You can also print out a colour wire diagram for your car from this site.
http://www.advanceautowire.com/mgb.pdf

Kent
DK McNeill

Fred,
Thank you so much for the detailed information. You have answered my questions with great satisfaction. I will plan to convert to the mechanical gauge as suggested. Also, thanks for the link to the wiring diagram, Kent.

Eddie
Eddie Haynes

Follow-up question: Can someone tell me where to find the voltage stabilizer (1968 MGB)that a number of gauges feed off; and is it easily accessible? I would like to check this out; the part seems to be reasonably priced if needing replacement.

Thanks,

Eddie
Eddie Haynes

You should find it behind the tach and speedo, mounted on the firewall under the dash. RAY
rjm RAY

Thanks, Ray. I'll be looking for it there.

Eddie
Eddie Haynes

This thread was discussed on 05/06/2010

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