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1980 MGB electrical problems

Last post 07-21-2008, 5:49 PM by Kimberly. 1 replies.
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  •  07-20-2008, 8:26 PM 15316

    1980 MGB electrical problems

    I have a 1980 mgb. Over 10 years I have had very few electrical problems. We live in an area where there are mice and they have caused problems with our other vehicles. I just started it up for the first time this season. Yes, go ahead and laugh. But it started right up. Then I noticed that the odometer, fuel guage, heater fan, turn signals, wipers and radiator cooling fans were all not operating. I ran a wire from the battery to the heater fan and the cooling fans and of course they were working fine. The 4 main fuses plus the 2 in individual fuse holders are all intact.

    I only partially understand how everything is connected. I am not sure which of these items are fused or how they powered. Are they powered from a terminal on the solenoid so they can receive power from the battery or alternator? If yes could there be a problem with the solenoid? Are they all powered through the ignition switch? I tried jumping across the terminals of the switch but that didn't seem to help.

    Also, when I ran power to either of the terminals of the radiator coolant thermostat, both the cooling fans and the wipers came on at the same time. And when I ran power to either terminal on the small 1" x 2" black plastic device with a wire connected on each side below the 4 fuse holder, the wipers also came on.

    I thought there mgiht be a problem with the wires to the wipers but at first glance did not see anything. I am thinking about disconnecting the wires to the wipers to see if that makes a difference. I am also thinking of running a wire to the cooling fans with a switch in-line and just driving it.

    I could definitely use some insight and assistance.

    Regards smiling smiley
  •  07-21-2008, 5:49 PM 15329 in reply to 15316

    Re: 1980 MGB electrical problems

    Wiring diagrams are available at http://www.advanceautowire.com  click on stock schematics.

    A common point of failure is the ignition relay.  They are available at most autoparts stores for less than five dollars.  Just ask for a generic four pin Bosch style relay.  Connect the black wire to terminal to pin 85, white wire to pin 86, white/brown wire to pin 87, and the brown wire to terminal 30.