Intermittent electrical issue

[W4RLR]

The battery idiot light will briefly flash, and the Scangauge will show a voltage between 11.6 and 12.2 at startup, then voltage shows 13.1 to 13.9 once the engine warms up. While at normal operating temperature, the light will again briefly flash for less than a second. Found a bad battery and replaced it, both alternator and remaining battery tested good.

Anyone else have a similar problem or advice on what to look for?

Thanks!

 

[BIG JOE]

Yer call Rich, but you Should replace the remaining old "Good" battery.. or yul soon have more 12v power issues. Preferably with the same brand, type, group and if possible.. a Twin in age (Build Date) to the New battery.

You should be seeing 14.?, a short time after a cold start. The 13.? could indicate that the remaining old "Good" battery could be pulling the new replacement battery down to a combined amp load the alternator can't handle ?

Jus' my .03

Joe

 

[W4RLR]

Thanks Joe. I get my batteries from O'Reilly as they sell the Motorcraft OE batteries. The battery I just replaced was warrantied so it cost me nothing. I will double check the other "good" battery, it's less than a year old.

Found an unnecessary electrical load today, the electric vacuum pump was running constantly as the connection between the pump and the vacuum tank was broken. Replaced the vacuum line and now the A/C and ESOF work again. The pump would come on at start and never shut off.

Will see if things improve now that the vac pump isn't running all the time.