Voltage and Oil Pressure Drop

[mrswivlepants]

Need some help fellas
Car runs decent but after about 15 minutes of driving the battery light comes on. When I stop at a light the battery voltage drops really low along with the oil pressure. Sometimes one will drop and the other won't but it typically happens at the same time. The idle doesn't drop really much at all when this stuff happens. I replaced the alternator about four months ago. This started happening around then so I yanked the alternator and got it tested and it checked out. The battery is charging so I don't think it's a failing alternator. Here's the tricky part, perhaps stupid on my part...I'm running a 500W amp off of the stock setup. This could obviously be the problem, but I didn't notice any of these symptoms when I first put the amp in. Problems only appeared several months later.

 

[88-GT]

Im thinking the voltage drops are messing with sending units. Go spend the 10 dollars and get a mechanical oil pressure guage, not really something you wanna guess about.

 

[jerryD]

hook up a meter and see what the voltage is at idle and at around 1500 RPM. i think that if you see anything at less the like 13.5, you are not charging the batt.

 

[mrswivlepants]

The voltage is good at idle when I first start the car. Assuming it drops below 13.5 after I run it and get the regular symptoms, what next?

 

[HISSIN50]

have you disconnected the power to the amp to see how it does (to rule out the amp and associated wiring)?

i did not see the year - it would matter for gauges, as early aero foxes had an IVR.

also, do you have an upgraded alternator? if so, did you upgrade the motor ground? if not, as 88-GT was getting at, you could have ground deprivation issues.

good luck.