Pre-start electrical issue - Ford Powerstroke Diesel Forum
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Old 03-08-2011, 06:58 PM
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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). Iíve got P0640 before so Iím not real worried about it, and based on the previous paragraph I wasnít surprised to get Low Voltage.

Since the PCM is functioning enough to give me codes, can I rule it out as the problem? Iíve done my best to read all the posts about specific problem areas in the wiring but itís 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.
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Old 03-09-2011, 06:46 AM
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First, I'd start with the batteries. SEVEN VOLTS is something you should NEVER see

Take 'em out, charge 'em up, and have them individually Load Tested. If they're good, scrape, clean, & grease all the connections and reinstall.

The draw is actually hard to measure because it takes up to 1/2hr, with everything undisturbed to settle to it's level. So, it depends how long after you've opened a door, rolled-on the key, or connected the battery before you try to measure the "static" draw.

Have you taken a good look at the Gem Module and Fuse Panel for signs of water? Windshield leaks, that end up dripping on that area, are not uncommon.

Low Voltage causes a myriad of problems on these trucks.... You can be chasing a wild goose while it's as simple as a bad battery
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Old 03-09-2011, 06:52 AM
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Yep...id look at batteries first as above...have em load tested.

7 volts is bad juju. Glow plugs and starter both on my voltage drops to 11.5....
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