Have a 98 f 150, 4.6. New battery , alternator,belt,plugs, injectors,hoses, fluids and filters. Battery won't hold charge overnight. Hooked up ammeter at 10a setting in series with neg battery post and neg cable. Initial reading was .030. Pulled all fuses inside cab with accessories off and doors closed, with no change. Moved to Power Distribution box and pulled fuses until fuse #22 (50a), saw ammeter reading drop to 0.0. Manual says fuse services Junction box fuse/relay panel, battery feed. Based on previous threads this refers to the in cab fuse box power lead. I removed Power dist. Box to see underside and wires wrapped in conduit. Wiggled all cabled harnesses heading into firewall ( after replacing suspect fuse ) looking for fluctuations on ammeter with no results. Harness is protected by conduit, no results on ammeter when I wiggled harness. No visible signs of damage. Sure could use some advice on what to do next. Is my reading of .030, enough of a parasite draw to cause problems? Have seen several similar posts, but none reporting resolutions. Grateful for any assistance!

 

You have to wait 40 minutes after touching ANYTHING for the GEM module to time out. Otherwise, you'll end up chasing your tail trying to figure out why there's a current draw when it's actually completely normal.

 

Well I'm feeling a little stupid. Attempted parasitic draw test again today. rolled down windows, left truck alone for 1hour , everything off. Removed negative battery cable, but kept ammeter probes in contact with terminal post and cable without breaking series connection, clipped probes onto cable end and post and...... NOTHING zero.zero. Test unit set to 10a, probe cables correct....0.0 on meter. No parasitic draw? Original premise started with toll free call to tech hotline from new alternator brochure in box. Hum.... "sounds like you have a parasitic draw", he said. Next I'm off to work trying to learn what that meant. Todays test after allowing memory charges to disband....0.0 . On the day first day after new battery and alternator installation, while driving home 10 miles from work, one glance on dash battery voltage gauge indicated about 13-14 volts. Ten minutes later, I looked again, 8 volts and falling. Just made it home. Today a neighbor walked by and suggested I pull battery cables off while running the engine, which we did. Engine promptly stopped. His assessment.... a bad alternator. If the ammeter readings at 0.0 are correct, could this simply be another crappy rebuilt alternator? signed...SERIOUSLY THINKING ABOUT CHANGING MY SIGN-IN NAME. ps have seen your numerous contributions to electrical victims and hoped you'd still be listening last night. Thx 089.

 

It's entirely possible to get a junk alternator out of the box, especially if you buy a "cheap" replacement part. Some guy's on here insist you should only buy OEM parts, I don't agree with that. However if you're using a cheaper option as the price goes down the odds increase you'll get a lemon.
You could get it tested at a parts store to verify it's no good. I can't recall off hand what the process is to test the amp output with your multi-meter, but with the truck running and your meter in the 20v range you should see around 14v at the battery if memory serves.

 

I don't know off the top of my head what the quiescent drain is supposed to be on your truck.

Generally speaking 0.020A or less is desirable. Most cars are around 0.012A


Pulling the battery cables on a modern vehicle with computers isn't the best option as a test method.


Before starting any charging system diagnosis, or really any electrical problem you need to verify the battery condition and state of charge.

 

The factory service manual allows for up to 50 mA quiescent drain for a PASS.

I developed the habit of always requiring the parts store drone to test any alternator or starter before I carry it out of the store. The last alternator I changed, on my '00 2.5L Conturd, had failed. The local Oreillys had the alternator on hand but it failed the in-store test, saving me a substantial amount of work in replacing the alternator twice. On that car, the alternator is jammed up against the firewall and I had to drop the Y-pipe and remove the passenger drive shaft and pull the tie rod out of the knuckle. This is NOT a job you want to do over because of a faulty replacement part.

Pick up one of those inexpensive voltmeters that plug into the cigarette lighter. They cost $12-15 at Walmart and can give you a good idea of whether or not the charging system is working with just a glance.

 

Good advice SHO89, it's a great idea to have them test a starter or alternator before you leave the store.

 

Okay.... Great advice from Patman, 1972-2003150 and ProjectSHO089. My second attempt at the parasitic draw test where I received a 0.0 reading on the ammeter EVIDENTLY WAS A MISTAKE. Bought an unpowered electric probe, connected to negative terminal and then to same cable, and the bulb lit up. Indicating electrical current flow, when everything was turned off. Setting up and using the ammeter (set on 10a) indicated 0.03 (30mA) , like it did on the first attempt. So its clearly I had a Parasitic draw of 0.03 (30mA). Went back and pulled every fuse again. Again the fuse 22 in the Power Distribution Box went to 0.0 when pulled. This was the Battery feed to the interior fuse/relay panel, so going to 0.0 isn't so crazy, I 'm simply cutting off all power to this fuse panel. When pulling the fuses from the interior panel, fuse 20 dropped from 0.3 (30mA) to 0.2 (20mA). This fuse protected the PCM, CTM, and the General Electronic Module. A second fuse, fuse 15, dropped from 0.03 to 0.0, when pulled. This fuse also serviced the General Electric Module. Could a bad GEM give me the 0.03 (30mA), resulting in overnight battery drainage? Dealer item? ProjectSHO089 said Up to 0.05 (50mA) was "passable". Should I be looking for a thread on GEM diagnosis, or do I have enough evidence to replace? Should I still be looking at the alternator? Input please ! As usual, your help is greatly appreciated.

 

You are measuring amperage in series right?

Can't be in parallel, that's not how current flow works

 

Yes sir, absolutely in series.

 

If your battery cannot supply 30 mA overnight, it's a dud.

It would be expected that the radio, PCM , CTM, and GEM module all draw some power when in sleep mode. The first three have keep alive power supplied for internal memory. The GEM or CTM module has the remote keyless receiver and, perhaps, perimeter security system, that have to stay awake.

I think you're chasing your tail trying to find a problem where none exists.

 

I'm with SHO89, since the only "draw" your seeing is what is normal for your truck when it's shut down. It's one of two things, and to be honest the most likely is a bad battery. But for due diligence testing the alternator to be sure it's producing the correct amount of current to charge the battery AND power the truck while it's running will prevent further chasing of your tail.

Remember, as several of us mentioned, you can get a bad part EVEN if it's new. Have the alternator and battery tested, I bet you'll find a problem with at least one of them.

As an example, my brother and I went around in circles with his V6 pontiac. He had installed brand new coil packs in it, it developed a miss. Put in new plugs, still there. New wires, still there. I suggested we test the coil packs, what do you know, one of them was junk. Replaced it miss went away. Turns out he spent about $100 on parts he really didn't need.