Erratic readings on ammeter: Bad shunt?

[gash]

I am getting very erratic ammeter fluctuations on my JPI EDM-930 in the Saratoga. Amps are rapidly changing between 20 and over 70 amps (no change in actual electrical load...it's just an erratic indication). Any ideas what could cause this? Today I checked the connections at the battery terminals and both sides of the ammeter shunt. Everything is tight. Could it be a bad shunt? Do shunts wear out or fail?

By the way, another bad thing happens on the EDM-930 when the amps fluctuate wildly. The EGT and CHT indications fail one-by-one from left to right. If the amp reading settles down, then the EGT and CHT indications slowly come back to normal. Annoying.

 

[TEG916]

 

[gash]

 

[TEG916]

 

[N4655R]

 

[Ray93J]

 

[Tweety]

 

[Lantraxco]

 

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[kgreen]