TAC Tech => Electrical => Topic started by: bongo on September 13, 2018, 05:32:22 PM

Title: Power draw
Post by: bongo on September 13, 2018, 05:32:22 PM
Hi all

Well flat batteries seem to be my issue at the moment.
I have done a draw test and without removing fuses I sit at 1 amp no ignition on.
Removing fuses I found the "heater" circuit has a draw of .6 which then leaves the vehicle with a standby
of .4 which is with in spec.

My question is: Is there a common fault location for this circuit or should I just start the hunt ?
Thanks
Title: Re: Power draw
Post by: firebirdparts on September 14, 2018, 06:13:34 AM
You might expect to find the dome light, glove box light, trunk light on.  A power antenna might be something to suspect.  Bad diodes in the alternator can draw big amps in any car.

Other than those obvious items, I can't think of anything.  I would say 0.4 is way too high.  Does your clock run?  A lot of them don't these days.  What year is the car?

P.S. I would also add I don't think the heater fuse drawing power is all that common.  The heater wire itself has a dedicated set of contacts in the ignition switch, and if those don't open, the fan would run.  There may be some other items on that fuse, but I don't remember.
Title: Re: Power draw
Post by: bongo on September 15, 2018, 04:47:41 PM
Thanks for the reply.

Yeah the clock still runs 78 FB.
Most sites on auto elec state that a low current draw is acceptable about.4 thats why I said what i did.
I removed all lights to ensure no circuit leakage as a first thing as lights was what I went to as well.

Guess Ill have to dig up a diagram and start tracing.
I am assuming disconnect the alternator to check for bad diodes whilst running?

Yes, I thought the heater circuit would only power when the switch is activated... alas I was wrong.
Title: Re: Power draw
Post by: firebirdparts on September 15, 2018, 06:47:36 PM
I don't think having it running would help at all. If you unhook the charge post while you are checking power draw, you will see if that helps you.  If you want to.