I've had this tac for 9 years. The sequence was always been turn key a quick beep, 4 lights come on and go off in sequence. start engine, 4 lights come on and go off sequenc. late last year that second started sequence became intermittent and somtimes did'nt appear all day. Just had a new 177107 installed, the new tac also sometimes misses the second (started) sequence. I was told by the installer (to his knowledge) that the tac is only supposed to display the pre start display, But as stated the new tac sometimes shows the started sequence. Can anyone establish how the light sequences are designed to function? Or is there a potential that it is not the tac but an engine sensor? Thanks all.
In most cases the 4-light self-test sequence only happens once when the key is turned to ON. If the voltage in the system while cranking falls below about 9-1/2 volts, the gauge reboots and the sequence starts again.
Often weak or too small capactity cranking batteries, faulty cables, or loose wiring connections are the cause of the lowered voltage. There should not be any wing nuts on the batteries, hex nuts and lockwashers only. Be sure the batteries pass a load test for a minimum of 800CCA for best results in all weather.
A tech can perform a voltage drop test in the starter circuit and the B+ circuit to pinpoint a source of resistance.