Tom M'Guinn

As reported the other day, I realized my a/f ratio changes with electrical load. I had a few minutes to check voltages this morning and found the following:

On battery terminals, at idle: 13.8 volts +/-
Power to ARC2 & MAF, at idle: 13.3 volts +/-
Power to ARC2 & MAF with heater fan on, at idle: 12.9 volts +/-
Engine off: 0 ohms between ARC2/MAF ground and neg battery terminal
Engine off: 1 ohm between engine and neg battery terminal

Where are my volts going?

Other data: with the positive probe on the + battery terminal, and the negative probe on the cam tower, I actually get slightly more power than when both probes are on the battery terminals (about 13.9 compared to 13.8) -- is the alternator power having a hard time getting back to the battery?

Edit: For those with bad grounds, were you able to see resistance in the form of ohms between the battery and engine? Any tips for testing the positive side of the harness?

badass951

Well just looking at that data right there your only current problem seems to be the neg battery terminal to engine ground. 1 ohm is definitely too high, it should be very close to 0 ohms. With the engine on, static voltage should be much closer to 14.4 volts and above. I think you definitely have a ground issue. Cleaning the grounds and retightening can usually do the trick. However, you could do a voltage drop test from one side of the ground to the other, as opposed to the resistance test you did. The voltage drop here should be as close to 0 as possible. I think you have found your problem already, so just work on cleaning that area up.

With the heater fan on you are only losing .4 volts, and parasitic draw typically allows for .3 volts of draw, so you are fine there.

Tom M'Guinn

1 ohm is too much resistance from battery to engine, really? Sometimes I get an ohm or two just touching the probes leads to each other... I will check for voltage drop to the engine, good idea.