Battery Discharge..

SCOBRAC · #1 (**permalink**) 01-14-2002, 05:19 PM

First I would like to tell everyone here here how much I appreciate the useful information I have found in the Forum. Although this is my first post I have read many hundreds of posts and several thousand replies and I think there are some really great tips and information to be had here. And the price is right as well.

A very long story short. I just got my first Cobra from a guy with more money than sense and recently he lost what money he had. The car is Contemporary #3152. It is BRG with Wimbeldon stripes. It sports a 428CI FE powerplant, 8v med. rise with Holley 4160, 450CFM carbs. The guy I bought the car from told me it was built in 1988 by Don Borders of Southern California. Since 1992 the car has been neglected first by the owner and unfortunately, several "good" (at stealing?) mechanics. The car is outstanding overall but has a few very strange quirks I am trying to sort out. I have three questions really.. Here goes.

1). Does anyone know a decent resource for learning more about Contemporary's in general and / or what a Contemporary wiring diagram looks like.

2). My battery, 650 cca deep cycle, with #1 gauge cables and NO electrical accessories (amp meter, coil, regulator, and alternator are the only potential drains) will be completely dead after 48 hours if I leave the battery terminal hooked up and the ignition switch off (if the terminal is unhooked no discharge, obviously)
the alternator is a new three wire autolite with a white a yellow and blue wire. voltage at the alternator is 15.2, at the battery I get 13-14.5 at 2000 rpm.

I guess my though is that I need either a diode or resistor wire inline to the alternator and am wondering if Contemporary would have done this, or would that be up to the builder? Is it common for this to happen and I should just use an isolator switch? As I mentioned the former owner was no help and actually may never have had a working charging system as the vehicle has been driven fewer than 20k in fourteen years and not at all for the last four.

3). Any opinions on the carbs? a total of 900cfm but they are mechanical secondaries. I have no problem with Holley's having grown up on them. The V/E V. CFM seems right for a street car but I am wonrering if a vacuum secondary system would be more driveable and give smoother power delivery. Does anyone here use a med. rise Ford 8v with 600-750ish vacuum secondaries. Is 1200-1500 cfm too for a street car?

Thanks in advance. Sorry this post is so long..

zimmy · #2 (**permalink**) 01-14-2002, 06:14 PM

I own a 10 year old Contemporary. I have the original build manual. I would be happy to copy the wiring diagrams, etc. if you need them. Please send me a email with your fax number if you want them or give me a call any time to talk about the car. (703-737-7760)

zimmy@knight-hub.com

Corey Zimmerman

SCOBRAC · #3 (**permalink**) 01-14-2002, 06:59 PM

Wow.. yea.. I wonder if a fax will be clear but you can try.. I'm at 707.449.4528 or thestrunks@prodigy.net Thanks for the effort. I really would like to chat with you sometime. I will e-mail you a couple photo's and the whole sad story if you are interested. I will be loading a few photo's onto a gallery here at the club too as soon as I get the time.

ERA535 · #4 (**permalink**) 01-14-2002, 07:56 PM

Put a voltmeter across the battery terminals and see what kind of discharge there is.

SCOBRAC · #5 (**permalink**) 01-16-2002, 07:12 PM

I lose between .5 and .6 volts upon energizing the system verses isolating the battery... any ideas??

a427sc · #6 (**permalink**) 01-16-2002, 08:48 PM

Pull the positive post and hook the v meter in line. Any voltage showing with everthing turned off? If so, start by pulling one fuse at a time to isolate the offending circuits. Check for electrical components that have a small draw when off, such as radio memory etc. Once you find the circuit, track down individual pieces with the wireing diagram and disconnect one at a time.
Sounds easy, wish it was.

Don

Cobra20646 · #7 (**permalink**) 01-17-2002, 08:03 AM

Michael,

What Don said is true, but to get a better handle on your problem, you need to measure the current drain.

With Don's test, your opening the circuit and measuring the voltage acrossed the open circuit. If there is absolutely NO current drain, you will measure ZERO volts. But, if there is even the smallest current drain, you will read the full battery voltage. A dead short circuit will measure the same..... so this test leaves something to be desired.

If you have a standard volt-ohm-current meter, open the positive battery lead like Don stated, but connect the meter in line to read current. Start out with the highest range available. After connecting it, reduce the range to read the current draw. A few milliamps is not reason for concern, i.e. the memory in a radio or a clock or ECM if equipped. If you do not have many accessories like you stated, I would expect to see zero current. Then, as Don stated, remove fuses and/or disconnect power leads from the various electrical devices on your car to determine where the excess current drain is coming from.

Let us know what you have found, we're all here to help you solve your problem.

- Jim -

John McMahon · #8 (**permalink**) 01-17-2002, 12:22 PM

Michael,

Email me a FAX number and I'll send you a copy of the Contemporary wiring diagram.

In regards to Contemporary history.....

If you do a search on Club Cobra with the word "Contemporary", it should come back with all the threads on this site where Contemporary was mentioned.

bran3b · #9 (**permalink**) 01-17-2002, 02:01 PM

Michael,

Does you carb(s) have an electric choke? If yes, make sure that the choke is only powered when the key is on. An electric choke can cause an almost unnoticeable power drain, but can drain a battery over a few days.

Good luck,
Bran3b

Jack21 · #10 (**permalink**) 01-17-2002, 07:59 PM

Some small device is draining your battery. A courtesy light, dash light , electric choke, backup light, ignition CD box. Start with the fusebox, pulling each fuse out and see which one has the circuit draining the battery. And, it may not be a fused circuit at the fusebox.

SCOBRAC · #11 (**permalink**) 01-18-2002, 10:08 PM

I had pretty much done what you guys suggested before consulting the forum and everyone of the suggestions are winners. (they have all worked for me in the past)..

I agree, the voltage is so low and the loss is so slight it is like a very small appliance, dome light, choke, ect.. is causing the problem. I wish it were so. This car is all business. No back up lights, no choke(s). While that makes the problem much simplier it also makes it tough. Keep in mind it is a three day process to try and isolate it and then recharge the battery to try something else.

I will take one of you up on your wiring diagram offer. I appreciate all of your advice and guideance.

Cobra20646 · #12 (**permalink**) 01-19-2002, 06:03 AM

Michael,

This kind of trouble shooting is what I do everyday.... on equipment that is more complicated, so I'll try again and give you a step by step procedure to follow and maybe we can pin this down...

First, hook up the meter to read current... set the meters range switch to the highest current range; remove the positive lead from the battery, connect the meters black or minus lead to this cable and the meters red or positive lead to the positive battery terminal. What is the current reading?

Second, hook up the charger to the battery terminals and let it do its thing while we troubleshoot, it won't interfere with the tests.

Third, most Ford setups run the positive battery cable directly to the starter solenoid. At this terminal, remove ALL the cables connected to this junction terminal being very careful not to let any one of them contact any part of the frame or other grounded metal......... the current should have droped to zero. If it didn't, start looking for a break in the insulation covering the battery positive cable. If the current went to zero (like it should have) continue on with step four.

Fourth, first connect just the battery cable to the solenoid. Check current, if you read any, replace the solenoid or check to see if it is installed backwards, if still zero continue on.

Next, of the remaining wires still disconnected, try to identify the one going directly to the alternator charge output terminal and connect this one now. Check current again, should still be zero.

Next, of the remaining wires, connect them one at a time and check the current after each connection.

One of these wires will be from a circuit that has become defective.

Report back with your findings.

The fact that this thing probably never was working correctly in the first place leaves room for the unusual problem to be present. From your posts, I assume that the car has no lighting, electrical gauges, turn signals, horn, electric fuel pump, whatever ... also, from your last post it seems you have confirmed a very small current leak. A very small current leak will not kill a battery in 48 hours unless the battery is BAD

- Jim -

SCOBRAC · #13 (**permalink**) 01-19-2002, 01:11 PM

Thanks Jim,

Of course the car has lights, but the reference was to back-up, dome lights and electric choke type acessories that while perhaps functioning may and could cause a minor short. The gauges, save the tach and ammeter are mechanical. I do appreciate the advice and will run down each lead at the selinoid as you suggest. The problem will be found there without a doubt.

I actually have, by a process of elimination, become reasonably certain the problem lies in the white wire off the alternator. This "exciter" wire while principally telling the alternator to function (with the key on) seems to be hot all the time. Hence my question, which originally related to the Contemporary owners and what sort of wiring harnesses they got with their cars verses the amount which the builder needed to fabricate. Traditional circa vehicles used a diode or resistor wire to isolate the circut. Left unisolated this small field, traditionally drawing .6-1.5 volts will kill a fully charged 650cca, deep cycle "Diehard" in, well my experience is 48 hours...

Thanks again everyone

Dave Samson · #14 (**permalink**) 01-19-2002, 05:58 PM

Jim,
I thank you too for your suggestions. I've just completed wiring in a junkyard Bosch ABS system using no more than a scavanged wiring diagram and had a few ground leaks which I found by elimination and rectified. I noticed that I have a small battery drain too and just connected my multimeter in series with the +ve battery terminal. I read 0.18A with my electric clock disconnected.
I have not run the car for 5 days and read 11.6V across the battery terminals. Any opinion ?

Cobra20646 · #15 (**permalink**) 01-20-2002, 01:57 PM

Hi Dave,
At first glance 180 milliamps doesn't sound like a whole lot of current drain, but that represents sucking 4.3 amps per 24 hours, which would completely kill a 100 amphour battery in something like 23 days..... ruff calculations here

Not wanting to pull figures from my head, I took my trusty Fluke multimeter and took a look at the standby current drain on my brides 98 Jeep Grand Cherokee...... just .015 amps or 15 milliamps or about a tenth of what your reading.
If you can determine the source of this drain (or the bulk of it) perhaps a quick and dirty fix would be to isolate this circuit with a relay and control it with the ignition switch. If there is no electronic brain that needs a source of power to keep its memory alive, this might be the easy way to go, rather than attempt to sort out the "correct" (by the manufactures standards) way to power it up.
Good luck....... this ABS project must be a labor of love....... I love a challenge too, but this would have me going bonkers in nothing flat. Take care
- Jim -

jwheel55 · #16 (**permalink**) 01-20-2002, 04:04 PM

Dear Scobrac
Whilst this isn't the total answer to your problem the fitting of a battery isolation switch is a good idea.Gives you the possibility of quick power disconnection in the event of a serious short or damage to feed cables . Plus it is a theft preventer to the opportunist thief. And whilst you car is stored less likelyhood of battery discharge. But of course the original problem needs sorting for peace of mind. Regards, Jonny

Dave Samson · #17 (**permalink**) 01-20-2002, 06:55 PM

Hi Jim,

The mystery is solved:

I extracted one fuse after the other and watched the ammeter:

Thermal switch sensor for electric water pump and 2ndary push fan activated without ignition draws 140 mA.
Alarm (even when not activated) draws 20 mA.
Old Smiths pendulm type clock draws 10mA.

I'll have to live with that....

Cobra20646 · #18 (**permalink**) 01-21-2002, 08:48 AM

Dave,
Thanks for the feedback. Shouldn't be too hard to clear up the draw from the pump/fan, and then the 30 mills from the alarm and clock should not be a problem.
- Jim -

PS how is the ABS coming along. Still in the sort out stage or is it installed and working now?

Dave Samson · #19 (**permalink**) 01-21-2002, 02:20 PM

Jim,
Will have to think about the draw from the pump/fan combo, don't know how to solve that one. It's my cool-down system after shutting the engine down. Since I don't run a mehanical thermostat, it circulates the water while the push fan cools the radiator until the dialled-in temperature is reached which usually takes a couple of minutes.

As for the ABS system, today I'll conect the hydraulic actuator and with a lot of luck, it will work. I also have to replace the master cylinder with one that is specific to the ABS system and in addition, I'm plumbing in an adjustable proportioning valve for the rear wheels. The ABS ECU is not programmable and I have a 6% larger wheel circumference on the back. This is the limit of tolerance that this ABS system can accomodate, therefore the proportioning valve.

Cobra20646 · #20 (**permalink**) 01-21-2002, 02:51 PM

Dave,

An electronic timer that you can buy (or build yourself if your handy) set to keep the fan/pump running for "X" amount of time after you switch off the ignition will solve that problem

Any electronic part stores down under? Couldn't cost but a few bucks to roll your own. I have one that I built that keeps the two-way radio on for 15 minutes after I turn off the car. If you want to try, let me know your address via e-mail and I'll send you a drawing.

- Jim -