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Old Jul 23rd, 2018, 16:23   #8
Ron Kwas
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Graham;

Your symptoms are consistent with a Voltage Stabilizer fault...to locate VStab, have a look at back of Tach or Speedo with a good light...sorry, they hid it pretty well, so some contortions are required...factory typically fastened them as a secondary use for the instrument securing hardware (giving continuous conductive path down to Dashboard metal)...but there might have been variations from the factory or mechanics which came along later...so remember: The Wiring Diagram Color Code is your friend...use wiring colors to verify you have indeed located the VS!...[White-GreeN looks to be input and BLue output for ES]
Be also aware, the Mount (M) hardware also acted as a chassis connection (important to the correct elec function of the VS!) so first thing when you locate it is to loosen, then resnug the securing nut to assure a good chassis connection (poor connection at VS mounting tab and any associated mechanical/electrical conductive path to Dashboard metal will cause malfunction including intermittency, although the "Chassis Tab" (C) of the VS itself simply wraps around the board edge and is held in-place by crimped over VS housing (see VS construction details below):

Source: https://www.sw-em.com/voltage_stabilizer.htm
...this connection itself is susceptible after such a long time, to corrosion...)...to check function of VS, locate and connect a temporary test wire to the output of VS (best place is at one of the other instruments), and monitor voltage...VS output should be consistent with that shown in link (thanks also for reference, C1800!).

Let us know what you find!

Good Hunting!

Arcturus; Fuel Gauge with apparent Parkinsons (beyond that of simply following the bouncing float) on a model without a VS is another subject and you should probably open a separate thread. See also: https://www.sw-em.com/Fuel%20Gauge%20Notes.htm

Last edited by Ron Kwas; Jul 23rd, 2018 at 18:18.
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