Mk1 mystery wires

Discussion in 'Mk1' started by Jamie Rossiter, Jul 22, 2020.

  1. Jamie Rossiter

    Jamie Rossiter Paid Member Paid Member

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    I recently got my 1983 mk1 gti (DX) back on the road. After a month of just enjoying driving her again I thought i should tackle the long list of electrical issues. These are:

    - Oil warning light constantly flashing.
    - Oil warning buzzer Goes off randomly. When first back on the road this was constantly chirping away, but now it’s off more then on.
    - Wipers slow ( this may be mechanical)
    - Heater fan blower doesn’t work on speeds 1 & 2 and blows the fuse on 3.
    - No mpg reading on mfa.
    - Wipers work with ignition off

    I appreciate that many of these issues have already been discussed in detail within other threads, but what I cannot work out are these loose connections in the engine bay. The first is a two pin connector with a blue/red wire and an earth. This comes out of the bulkhead and although I’ve not had a chance to trace it back, I assume it comes from the fuse box. I cannot see where is should plug into. Any ideas?

    The second is a single brown and white wire which has a ring terminal crimp on it (defo not standard). This is part of a loom which comes out of the bulkhead behind the dash. I’ve checked continuity and is an earth connection, but I cannot see what it should connect to. Any ideas?

    FC917C76-07A2-4DE3-ADAB-934359D408FA.jpeg DC4ED17D-264E-4C60-90B1-825CE794B7EA.jpeg
     
  2. 2swe Forum Member

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    the first connector with blue-red and earth wires, is for coolant level sensor. if you bridge the terminals, engine temp gauge should go full hot with warning light on.
     
  3. rubjonny

    rubjonny Administrator Staff Member Admin

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    2nd the picture is too small to see clearly, but if its brown it'll be an earth for something 9 times out of 10. I see the 3 pin plug which joins the engine loom side to gearbox side for the MFA gear and vacuum switches, might be for those?

    1. or oil warning check the switch wires and switches themselves. on the side of the head you should have a blue or brown 0.25 or 0.3bar switch with a yellow wire. this triggers the light with ignition on and while idling if pressure is low, if you disconnect the wire this warning is disabled and if you earth it the light should stick on. then on oil filter housing you should have 2 white sensors, the small one is for MFA oil temp and has a green/black wire. the larger one is the 1.8 bar oil switch and should have a blue/black wire, if you disconnect it the light+buzzer should come on over 1.8k rpm, if you earth it the oil light+buzzer should never come on when revved up.

    2. strip and clean up wiper spindles to start with, but might be wiper motor. if so, mk2, mk3 and early mk4 golf motors fit, you'll need the 5 pin plug to match to splice to your wiring for the mk4 golf the early one has a white 5 pin plug with only 4 wires, you need to add the 5th wire. late only has black 4 pin plug and is no good to you.

    3. take grille off blower motor and try jumping the motor direct with 12v from battery. if it doesn't move give it a wiggle back and forth see if it starts to free up, then try again. once spinning spray grease at it roughly where the bearings are till it spins up to full speed, or remove the motor entirely and clean up on the bench. if the motor wont work no matter what replace it. if motor works perfectly when jumped and still wont when plugged in check blower switch and wiring, also look at the resistor.

    4. check vacuum pipe from inlet to clocks, make sure the distance and average speed settings work. if its the big mpg needle you're talking about this comes back to the gearbox and vacuum switches I mentioned earlier, the vacuum switch should trigger the upshift light and the gearbox switch should earth when in 5th to trigger the needle

    5. check if the blower motor (when fixed) also work ignition off, also heated rear screen. if they do, you have a short to x-relay circuit somewhere
     
  4. Jamie Rossiter

    Jamie Rossiter Paid Member Paid Member

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    Thanks 2swe, this makes sense as the header tank doesn’t have the sensor fitted.

    Thanks for the info Rubjonny. Apologies for the poor quality pic, it was clearer on the phone. The brown and white wire isn’t connected to the 3 pin plug, but perhaps should be. I need to take the instrument cluster out anyway, so will trace it back.
     
  5. rubjonny

    rubjonny Administrator Staff Member Admin

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    ah sorry brown/white will be the earth for the MFA clocks so put a ring on it and attach to head :)
     
  6. Jamie Rossiter

    Jamie Rossiter Paid Member Paid Member

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    Thanks rubjonny :thumbup:
     

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