Ive been having a battery drain prob ever since installing autometer tach, boost and oil pressure guage, could the memory for the tach be draining my battery, It's a autogage by autometer with shift light. The car sits for a week or two at a time, if driven regularly there is no problem..
If the tach is properly installed, it gets power from a switched source like the ignition coil + terminal.
Typically it is something draining the battery. Small things like glove box or courtesy lights are often the culprits. If you have an aftermarket stereo or alarm system, it is also suspect.
The ideal method is to disconnect the positive terminal, and connect a Digital Multimeter (DVM) between the positive terminal on the battery and the positive cable. Set the DVM on a low current scale of 2-5 amps if it doesn't auto range. Watch the current draw, and then start pulling out fuses. When you see a sudden drop in the current, that circuit is the likely culprit. Note that the computer, radio & clock will draw less than 1/10 amp to keep the settings alive.
I'd add that if this just started with the tach install and the tach has a battery feed for the memory, do JR's test but disco' the tach's battery feed first and see if that's the big draw.
If not, mow down all other circuits. Otherwise it's just too coincidental (I've learned that when something gets hosed after an install, I go back over my very last work to see what I screwed up. ).
thanks, my question is this, on the tach should the needle go to the shift light setting when the car is shut off?? When the battery is charged and I shut off the car , the needle goes to 5700rpm, but then the battery goes dead the needle goes down below 0 rpm. Maybe the wire for the tach is wired into a 12v constant instead of a 12v switched source.
If the tach needle isnt supposed to be at the shift RPM with the ignition off I'll just simply need to rewire it to a switched source
I have an air core AM tach and with the key off, it rests at zero, though I think they say that air core gauges dont always do so.
If there is only one power wire (not an accessory and a memory wire), I'd definately do as JR outlined and you mentioned, and wire it so it's only accessory hot.
Looks like the tach was the culprit, got it over to a switched source and all is well, no more frowns when I turn the key, thanks jrichker for the info