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Electrical help: Draw on a truck

Posted: Sun Dec 27, 2009 4:53 pm
by Jay G.
Hello all!
My own personal truck is a 99 ford explorer xlt. I have 3 CDM1550's and a bunch of lights installed, NONE of which stays on when the car shuts off.
I have been experiencing a dead battery too often lately, and want to make sure its not something aftermarket or just simply a bad battery. I just went fuse by fuse on all the aftermarket stuff to find NOTHING drawing over .04amps when the truck is off. Im pretty happy that this is normal.
I then disconnected the battery and put my meter across, to find that the whole truck is drawing .38 amps with the truck off. Is this normal or is there something else like from the factory which is drawing too much.

Any thoughts??

Thanks & Happy Holidays to all!

Re: Electrical help: Draw on a truck

Posted: Sun Dec 27, 2009 5:10 pm
by tvsjr
You're on the right track... no, 380ma isn't acceptable. Think about it - a car battery is about 50Ah... 50Ah / 380mAh = 131 hours to battery exhaustion. Considering vehicle starting demands, you'll have a no-start condition long before the battery is totally exhausted.

So now you need to figure out where the load is coming from. Disconnect everything aftermarket and confirm the high parasitic load, then start pulling fuses and see when the load drops. Have a friend watch the meter, and pull each fuse then replace it. Sooner or later, you'll figure out which circuit is affected. Once you've isolated the problem, start tracking it down. A service manual may come in handy at this point.

You never know what weird things may cause problems. A friend of mine purchased my old Expedition... after enough years, he developed a water leak condition at the driver side of the windshield. The water will leak in and get into some of the vehicle electronics and create a similar condition... once it dries out, it goes away.

Re: Electrical help: Draw on a truck

Posted: Mon Dec 28, 2009 6:50 am
by jackhackett
When you measure the battery drain on an Explorer (and other Fords) you need to put your meter in line and let the vehicle sit undisturbed for about 45 minutes to an hour. There are some things in the electical system that don't shut off right away. If you disconnect the meter or open the car door it'll reset and you'll have to start again. If everything is working right you'll get an initial high current drain, 380 mA sounds about right, then it will drop off as the vehicles computers shut down.

Re: Electrical help: Draw on a truck

Posted: Mon Dec 28, 2009 7:31 am
by fineshot1
Jay - how do you have the CDM1550's hooked up to power?

I have two of these in my van and experienced the same thing until I discovered I had them
hooked up improperly. I had the main power wire on each hooked up to +12V hot all the time
and was not using the ignition sense (pin 10) on the accessory connector. This caused both
radios to draw current all the time and on the weekends I would have a dead battery after
not using the vehicle for several days.

I had to change the main power wire hookups to +12V ignition switched to kill power to them
when the vehicle was not in use and that solved my problem. I also had to short the accessory
conn pins 7 & 9 to get the radios to power up function once +12V ignition on the main power
cable was present.

Re: Electrical help: Draw on a truck

Posted: Mon Dec 28, 2009 7:35 am
by Jay G.
I think jack hit it on the head. I'm pretty sure it is the computers. I pulled all the fuses one at a time and lost over 210ma of draw from 2 of the computers.

Thanks to all!

Re: Electrical help: Draw on a truck

Posted: Mon Dec 28, 2009 4:29 pm
by tvsjr
jackhackett wrote:When you measure the battery drain on an Explorer (and other Fords) you need to put your meter in line and let the vehicle sit undisturbed for about 45 minutes to an hour. There are some things in the electical system that don't shut off right away. If you disconnect the meter or open the car door it'll reset and you'll have to start again. If everything is working right you'll get an initial high current drain, 380 mA sounds about right, then it will drop off as the vehicles computers shut down.
Yep, very true... plus there's also delayed accessory where things like radios and lights stay on for up to 10 minutes.

Re: Electrical help: Draw on a truck

Posted: Tue Jan 19, 2010 3:30 pm
by thebigphish
Jay,

I'm on my fourth Explorer so I'm right there with ya on the parasitic loads issue... How old is the battery, and which alternator do you have in it? With 3 radios, plus stock equipment, plus lights...you're probably over the stock generation overhead figured into the system.