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Discussion Starter · #1 · (Edited)
Hi all , our 70 SG nova has a older autometer monster tach w shift lite & recall & it was working ok till around time few days ago we installed a new AGM battery that’s about 850 CA. Autometer tach went to about 3500 from being 1500 and Once trans brake button was released it went quickly over 10 grand n pegged . Shift light acted off too due to false reading . My question is could low voltage make the tach read off like I described? Thx in advance!
Motor vehicle Gauge Speedometer Measuring instrument Font
 

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Discussion Starter · #3 ·
What RPM is the tach at with power off? Does it re-zero itself when you turn power on, before starting engine?
It zeros out with ignition killed & I just got back from putting my Mac timing light on it & it’s weird …. When idling at 1700 tach reads just under 3000 & when revved up to 3000 on timing light the tach reads 2260 so it may need sent in for a redo or upgrade , I’m thinking of trying a new non memory recall my son has for another project to see , all grounds are excellent & coil connection , it works just erratically, I also had a new 1000 CA lead acid battery for trailer winch few days old I put in & same scenario .
 

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Discussion Starter · #7 ·
Well figured out tach issue , it was the cylinder setting , had to press recall button & throw power on at same time & tach pulses between 2000-4000 & let go at 4000 = problem solved . Nice to have that fixed , moral of story , don’t push buttons till you know how they work , thanks all 🙏 & Happy Birthday America 🇺🇸 ❤
 
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