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Re: chasing an electrical draw
[Re: Andrewh]
#907342
02/07/11 01:38 AM
02/07/11 01:38 AM
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Joined: Oct 2010
Posts: 606
Montana
Yancy Derringer
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mopar
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Posts: 606
Montana
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The problem is there can always be potiential to draw voltage. so the light will come on.
you may be chasing a normal draw. Until you check to see how much current you are pulling you have no idea.
the fact your door switches make it burn brighter tells me you are not drawing much current right now.
no point in wasting time if it is less than .4 amps. But till you run an amp check, you have no idea and could just be wasting time.
THIS IS NOT TRUE AND MAKES NO SENSE
FIRST, there is NOT "always the potential to draw voltage" (so the light will come on.)
IF the system is "clean" that is, HAS no parasitic draw, the lamp will not light, PERIOD.
I'm speaking here using the "typical" parts store 12V test lamp, which typically uses something like a no57, or a cartridge type lamp
If it uses an LED or some other tiny "wheat" bulb, you may have a point
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you may be chasing a normal draw. Until you check to see how much current you are pulling you have no idea.
Once again, a "decent" 12v test lamp, like a 194 or 57, etc, SHOULD NOT LIGHT if things are normal. There is no such thing as a "normal draw" that will light a lamp -- in these old cars
I miss spoke, my point was what if this is a normal draw, not a short. I disagree that there are no draws even in old cars, that are considered normal.
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the fact your door switches make it burn brighter tells me you are not drawing much current right now.
This statement depends somewhat on how much current the test lamp itself draws. It could be very little, could be a lot.
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no point in wasting time if it is less than .4 amps.
This is about the silliest thing I've ever read. .4, ALMOST 1/2 AN AMP is a HUGE load for a car that may be parked for long periods of time. Let's say you have a 100 amp hour rated battery. Negating the "20 hour" rating, and just using straight math, this means that a 100 amp-hour battery WOULD ONLY LAST 200 hours!!! (100/ .5) THAT IS ONLY AROUND 8 DAYS!!!!
To put this into simple terms, IF YOU HAVE A PARASITIC DRAW OF .4 AMPS, IT'S WAY TOO MUCH!!!
my mistake, not sure where I got that number from, it was the number I remember, but might be .04. regardless, that number doesn't really work either. I expect my new car to sit 2 to 3 weeks with its normal draw before killing the battery to the point where I cannot start. Assuming a 50 amp hour battery, I would expect a draw of less than .14 ish, so I guess around .1 would cover me for 2 weeks and still leave enough to start.
Again, my point is, figure out how much draw you actually have before wasting time chasing it down.
IF it is not significant, then it isn't your problem.
Fair enough, but your "mistake" DOES raise some interesting points:
In this day and age of "Chinese" stuff, you need to make sure your test lamp uses a good, heavy bulb, instead of some puny "wheat" bulb or an LED drawing very little current.
(I actually use a tail/ stop/turn bulb for some troubleshooting, because sometimes you WANT to "load" a test. Also, one of these bulbs rigged into a dual contact socket is very handy for stuff like charging lightweight motorcycle, etc batteries, with oversized chargers)
You do need to follow up with an ammeter/ milliameter to see just what the draw IS in current.
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Re: chasing an electrical draw
[Re: Yancy Derringer]
#907345
02/07/11 01:21 PM
02/07/11 01:21 PM
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Joined: Jul 2006
Posts: 4,179
California
mickm
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Quote:
I would find a place to isolate the dome light wiring. The connector I mentioned in the previous post SHOULD be 3? terminal, and may be down coming out of the dash group near the left side, may be near the left kick. In other words it "divides" the dome light harness through the rest of the car from the fuse circuit.
I would suspect something like wet--corrosion --rust in, something like a door like switch, or deteriorated wiring harness "down wet" such as under the door sill(s)
I dont' remember if this harness extends into the trunk (trunk light) or not.
I wish to heck I could afford to travel. I'd love to help some of you guys with this stuff.
The problem is it's been so long since I've owned a 70 that I've fogotten a lot of details, nowdays.
i'd love the help! not even the greateer experience, but sometimes just a second pair of eyes.
i will have to double check, but i'm pretty sure that the dome light does not come off of this circuit. IIRC it is the following:
- emergency indicators
- glove box light
- delay timer
- clock light (maybe clock power?)
- and map light under the dash
from there, it seems that all of this circuit should be contained underneath the dash, but i'll check again.
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Re: chasing an electrical draw
[Re: Moparteacher]
#907346
02/08/11 01:22 PM
02/08/11 01:22 PM
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Joined: Jul 2006
Posts: 4,179
California
mickm
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The maximum acceptable draw for most manufacturers (industry standard) is 50mA. or .05Amps. Most late model vehicles draw between 10mA and 30mA. Your Roadrunner shouldn't draw much more than 10mA. We teach that anything greater than 50mA is too much!
since i know the draw is relatively small, i'll hook up my multi meter and see exactly what it is.
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Why is your LM1 wired into your cigerette lighter? Cig lighters are usually not switched through the ignition; they're always hot. This means your LM1 is always powered up.
it isn't. it's the portable meter, and when i'm using it i plug it into the cigarette lighter.
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Does the runner have power windows, locks, or seats? I've seen faulty lock and window switches cause a draw. The centering spring breaks and the switch will rest to one side. I've seen the same with the dome switch also. The switch is worn and metal spreads across the contacts just enough to close the circuit through the lamp but not enough to light the lamp.
good luck
no power windows.
again, i have to double check, but spent a few hours last weekend with it, so i'm pretty sure that the dome light is not on this circuit, but i might have missed it.
will see where this goes this coming weekend.
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Re: chasing an electrical draw
[Re: mickm]
#907347
02/08/11 02:38 PM
02/08/11 02:38 PM
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Joined: Oct 2010
Posts: 606
Montana
Yancy Derringer
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mopar
Joined: Oct 2010
Posts: 606
Montana
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If you have the original shop manual, Fig 30 "Instrument Panel Accessory Wiring Diagram--Belvedere
Shows coming off that fuse:
M5A 18P glove box lamp
M5 18P map light switch
X21 18GY clock
X1a 18P time delay relay
THEN GO TO
Fig 29, "Instrument Panel Wiring Diagram" Belvedere
shows coming off the fuse
"Emergency Flasher D31 18BK
which goes to the flasher, and a splice comes off --to--
D3-18P goes to stop lamp switch, with splice comes off --to--
M1-18P goes to far right of page a two pin connector labled
"To Dome light wiring (body)"
So one wire going to that connector is the M1-18P, 12V power to the dome circuit
The second wire in the connector is yellow, goes to door switch and headlight switch, provides ground leg switching for dome light.
THEN GO TO FIG 9
This connector seems to be shown on Fig 9 "Instrument Panel Main Harness Hook-up Belvedere
Down at bottom driver's side, shows connector with yellow and pink, down by "to headlight delay relay wiring" at bottom of page.
If you don't have these, I can photo them and post 'em.
Last edited by Yancy Derringer; 02/08/11 02:47 PM.
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Re: chasing an electrical draw
[Re: Yancy Derringer]
#907348
02/08/11 05:56 PM
02/08/11 05:56 PM
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Joined: Jul 2006
Posts: 4,179
California
mickm
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OP
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Joined: Jul 2006
Posts: 4,179
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Quote:
"Emergency Flasher D31 18BK
which goes to the flasher, and a splice comes off --to--
If you don't have these, I can photo them and post 'em.
i missed that splice. i do have the FSM, so i'll continue tracking this down now that i know that.
thanks 
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Re: chasing an electrical draw
[Re: mickm]
#907349
02/11/11 11:09 PM
02/11/11 11:09 PM
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Joined: Jul 2006
Posts: 4,179
California
mickm
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ok, so i found it, and it was right in front of me.
i have a repop tic-toc-tac, and it has 3 connections. 1 is power for the clock, 1 is power for the tach, and one is input signal for the tach.
with all of them connected, the draw is 79mA. since both the tach and the clock draw, and i wasn't disconnecting the feed to the tach last time, i still saw the light lit up, and thought that wasn't it.
just the clock connected is drawing ~3.5mA. the power to the tach is drawing the rest.
the thing is, the wiring diagram shows the power to the tach coming off of a different fuse, so it might be switched by the ignition. i'm not sure why it is getting power from this circuit, i'll have to trace it down.
so say 80mA on average. at 100 hours, that would draw 8 amp hours from the battery. 1000 hours would draw 80 amp hours, and 1000 hours is 41 days. this seemed to be going dead after 2 weeks or so, 14 days. 336 hours should only be a draw of 27 amp hours or so, if i have all my math right, (which i probably don't).
so someone posted that 50mA is the limit. i will call the guy i got the tach from and ask him about this, but that doesn't seem that bad.
don't these batteries have a couple hundred cranking amp hours?
so at least i've found it, looks like the thing to make sure that the power to the tach is either on the right circuit or get it on the right circuit.
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Re: chasing an electrical draw
[Re: mickm]
#907350
02/12/11 02:47 AM
02/12/11 02:47 AM
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Joined: Oct 2010
Posts: 606
Montana
Yancy Derringer
mopar
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mopar
Joined: Oct 2010
Posts: 606
Montana
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Quote:
the draw is 79mA.
!! GREAT !! So I assume you've re-checked, what's the complete system draw now that it's disconnected.
79 mills doesn't sound like much, but it adds up.
If you figure a 31 day month (car is parked for a month)
That's 31 days x 24 hours a day x .079 amps
That's a grand total of nearly 59 amp hours!!!
That's DEFINATELY enough to set a 100 AH battery on it's a$$!!!
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Re: chasing an electrical draw
[Re: Yancy Derringer]
#907351
02/12/11 03:41 AM
02/12/11 03:41 AM
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Joined: Jul 2006
Posts: 4,179
California
mickm
OP
master
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OP
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Joined: Jul 2006
Posts: 4,179
California
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Quote:
Quote:
the draw is 79mA.
!! GREAT !! So I assume you've re-checked, what's the complete system draw now that it's disconnected.
That's a grand total of nearly 59 amp hours!!!
That's DEFINATELY enough to set a 100 AH battery on it's a$$!!!
with it disconnected, the draw is 0. mili amps anyway, might be some micro amps. but the clock is 3.5mA, so even that would add up over time.
now i just have to figure out what to do about it.
thanks for the help!
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