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Pre-start electrical issue
I hate to be that guy whose first post is "my truck won't start", but here goes. Sorry if this is long-winded. Truck is a late 99 F250.
Sunday morning I go out to start the truck, and when I turn the key (havent't turn the engine over yet) I get this loud clicking sound that seems to be coming from under the dash. Wait-to-start light comes on like normal, but fuel and voltage gauges don't do anything. Tach reads about 700 momentarily (still haven't turned over engine) before settling back down. I decide NOT to try and turn the engine over. Take out the key and try again - same thing. Try a third time and the clicking doesn't happen, but the wipers start up (they are not turned on).
I test the battery voltage and it's right around 12, which is a little low so I tested for current drain. With everything off, I get around 240 milliamps. This seemed pretty high, so I disconnected the batteries since I wasn't going to do anything with it until Monday.
Monday I check all the fuses and relays (under hood and dash) and clean the terminals. Disconnected the gauge panel harnesses, pcm, wiper harness, and ignition switch and made sure they were all clean. After this I still had the same problem, but the battery drain was down to 120 milliamps. This still seems high, even though the manual says not to worry until 500 milliamps. When I pulled Fuse 22 (Instrument Panel Junction Box) from the under hood fuse box, the drain is zero. Is this what should happen?
When I turn the key on, the voltage goes down to around 7 at the battery. When I turn the key off, it gradually increases back to 12.2 volts. This is not good, right? Could this be a bad ground?
I used my Hypertech programmer to scan for DTCs and got P0640 (Manifold Intake Air Heater), and P0562 (Low System Voltage). I’ve got P0640 before so I’m not real worried about it, and based on the previous paragraph I wasn’t surprised to get Low Voltage.
Since the PCM is functioning enough to give me codes, can I rule it out as the problem? I’ve done my best to read all the posts about specific problem areas in the wiring but it’s been to no avail.
It also seems like the electric vacuum pump is louder than usual, but I might just be getting paranoid at this point. I disconnected the vacuum pump harness and it made no difference to the voltage drop after turning the key.
Any thoughts? Should I just continue looking for bad wires?
Thanks for reading all that and for any insights you might have.