Ammeter bypass questions

[Knebel]

Ok so I will work on putting the relay circuit together. The EFI is sensitive when the voltage drops to lower than 9volts on the switched wire. And that's what happens sometimes, when the car sat for a few days.... Damn interstate battery dosent seem to hold a charge that well when there is a tiny bit parasitic load on it.

 

[Gerald Morris]

Good thinking! I suspect you have a small short circuit, likely in the very wires we're discussing. I had a DOZEN or so little breaks, nicks and such in my 50 yr old vinyl insulation on the stuff from the starter relay and the headlight+battery wire in that loop. SNIP! SNIP!, and ONE nice NEW wire thru the firewall took care of those issues. If you've got time, get a good digital voltmeter and go around the dash and underhood checking various voltages. Start from your starter relay. Try disconnecting the battery, then do a continuity check. Check resistance to ground on those wires which give you a "ring" on continuity. HEY, did you check the windshield wiper hookup?! THAT's a likely sort of sneaky short we're hunting.

Do your relay setup for the EFI now, just to optimize available potential to it. You will still have a problem, but this should bypass it to a healthy extent. I had to hunt down my wiring problems over about 6 months, and I only now, about 13 months of happy ownership later, can say I'm confident in my wiring harness. I still need to setup my headlights on a relay too, but for the present my ELECTRICAL issues amount to simply upgrading and adding NEW elements, finally! You'll be happier when you get there too.

 

[Big_John]

the voltage drops to lower than 9volts on the switched wire. And that's what happens sometimes, when the car sat for a few days

That's quite a parasitic draw. You need to address that.
This will show you a couple good methods of finding a draw. The third one, using voltage drop across the fuse is really great and easy with our barrel type fuses.



This guy also does a great video on measuring voltage drop that I consider a "must see" for anyone doing electrical work.

 

[Knebel]

Thank you for the videos, they are very informative. I had measured parasitic draw before and it's was in a normal range, even unhooked the alarm system and it still drained. Even had it drain my battery in a few days, I have a small solar charger I plugged in now and haven't had a dead battery in a while...

 

[Knebel]

Installed the relay today. I'm now within 0.15v to 0.2v drop on my switched ignition. That's down a lot! I measured voltage drop across the fuses and had all between 0 and 0.1v. only fuse which had 0.5v was the security system.

But!!! I have a 0.6v drop between battery positive and the starter relay post. That's HUGE for some 6 inch wire going there. So my next project is, better battery terminal and wires/connectors.

Now question, can the 0.5v drain my battery empty withing a few days??? Or would that be an indicator, that my battery isn't that great to begin with, its an interstate I already got replaced a year ago under warranty (the old one only lasted a year too til a cell went bad)

 

[Big_John]

I'm now within 0.15v to 0.2v drop on my switched ignition. That's down a lot!

That's great!

I measured voltage drop across the fuses and had all between 0 and 0.1v. only fuse which had 0.5v was the security system.

That's not so great. Is it .5 volts or .5 millivolts? Even .1 volts drop across the fuse is a lot.

But!!! I have a 0.6v drop between battery positive and the starter relay post. That's HUGE for some 6 inch wire going there. So my next project is, better battery terminal and wires/connectors.

Aha! There's part of your problem.

ow question, can the 0.5v drain my battery empty withing a few days??? Or would that be an indicator, that my battery isn't that great to begin with, its an interstate I already got replaced a year ago under warranty (the old one only lasted a year too til a cell went bad)

I'm chasing a similar issue on my daily driver (2010 Mercury) and the draw, measured at the battery terminal was about 20 milliamps. This was enough to kill the crappy battery I have in about three days in sub freezing weather. The issue turned out to be some POS cell phone charger that Mrs. Big John insists on having in the car. I may have accidentally lost the charger today.. I've got it down to 5 milliamps and I need to replace the battery.

Anyway.. the voltage drops I was seeing across the fuses were in the .5 millivolt range... So, if it is .5 volts, then it would kill the battery pretty fast.

So... First, check if you are in millivolts or volts.

Second, I would pull the negative terminal, connect your meter in series (one probe on the battery, one on the cable) and see how much draw you have. Ideally, you should be under 25 milliamps (.025 amps). Actually... if you didn't have your EFI and security system, I would expect it to be minimal, if even readable.

 

[Knebel]

Oh... Mhmmmm I had the meter set to 200mV. It wouldn't show up at the 2000mV setting. So on the 200mV I have read between 001 and 003 across the fuses and 050 across the the security system fuse. So that would be 50mV right?

 

[Big_John]

Oh... Mhmmmm I had the meter set to 200mV. It wouldn't show up at the 2000mV setting. So on the 200mV I have read between 001 and 003 across the fuses and 050 across the the security system fuse. So that would be 50mV right?

That would be 50mV or .05V.... IF there wasn't a decimal point in there somewhere.

I think 50mV voltage drop across that fuse is very high. 5mV would be a lot... I would expect .5mV drop.

The 200mV scale on a 3 1/2 digit DMM reads out 00.0 to 99.9 and then when it gets to 100.0mV and then it reads 100.0 to 199.9 .

 

[Knebel]

I will go and check that again later. 50mV does seem a lot....

 

[Gerald Morris]

My sympathies to those afflicted w digital voltmeters with ambiguous "milli-" scale displays. I have one, but seldom use it, preferring good old analogue, jeweled d'Arsonval meters. I prefer instrument clusters similarly accoutred. Maybe my age is showing but I have no trouble knowing which scale to read on these.....

 

[Knebel]

So. On the 200mV setting it shows 00.1 on the EFI fuse, 00.5 on the Security system fuse. And 00.6 between battery post and starter relay post, but come tho think of it, the stereo is spliced in behind the dash somwhere, so that could be it too. My solar charger puts out somewhat 250 to 500mA in full sun which keeps it from draining, assuming it's waaaay less on the cloudy days we have. But since I had the solar panel, never had a dead battery. If I disconnect it, I cant start the car after sitting a couple of days.

 

[Knebel]

I need some more help here. After having the car sit for almost a week, my battery drops to barely over 10v. While cranking it goes to 8.xxVolt and that actually is too low for my EFI (my stalling issue after crank is based on too much drop on the switched 12v wire...). I'm gonna splice the blue and brown IGN wire together at the IGN switch, so that some drop while cranking will be eliminated too. Voltage drop between negative terminal and chassis and blood k is 0 to 00.1mV

I have in the past pulled the fuse for my security system and let the car sit for a week, same battery drain and there was a seperate thread about that too. So I don't think that's it. The EFI computer dosent pull enough to drain it that fast...

Weird thing is, the car was fine when I got a new interstate battery, after about a year,the battery started going dead, fully charged, it dropped to 5volts when cranking. Got it replaced under warranty about a year ago and car was fine. Now it starts acting up just the same. My charging system is tiptop and charges just fine.

How can I figure out if my battery just dosent want to hold a charge that great anymore? Would it be worth investing in a yellowtop optima? Don't want to Shell out the coin if it's not the battery...

 

[Big_John]

If you've been having this issue with the battery being discharged for a while, I would say you probably have a bad battery now.

As the battery discharges, lead sulfate forms on the plates. If it is discharged normally, like starting your car, charging dissolves the sulfate and all is good.

If the battery discharges, and isn't fully recharged right away, the sulfate turns to crystal on the plates that doesn't dissolve. As more and more crystal builds up, the battery loses some of it's capacity and eventually becomes worthless.

I have a load tester that I bought from Harbor Fright that I check batteries with. About $25. It basically puts a 100 amp load on the battery and checks the voltage. It's a good piece to have in your tool box.

The other, and probably easier alternative is to take it to your local Advance Auto/Auto Zone type place and they can check it for you.

Most likely, you are gonna have to buy another battery. I've heard people not being happy with the Optima... I would research that option more before investing in one. I think a trickle charger might be a good investment.

 

[saylor]

did you do all the wires per the guides?
1.) alt to starter solenoid relay post
2.) batt to starter solenoid relay post.
3.) relay post to dash thru firewall (red side)
4.) dash to relay post back thru firewall the other way (black side)

try not to die -

- saylor

 

[Knebel]

What I have done is engage a relay with the ign run wire and that feeds batter power directly to my junction for switched 12v. so my switched 12v now has the same voltage as the battery. Essentially having the power for that not go through the IGN switch (which I just fixed some big loose wire issue some idiot crimped in before me that could have been a desaster... the big wire for Acc came out of a buttsplice). I am no fan of those crimpers all my connections are always soldered and heatshrinked.

I have that solar tickle charger plugged in whenever I dont drive the car but that barely keeps up when its cloudy. I have no option to plug in a real tickle charger without taking the battery out but I have a charger and this apartment complex here is horrible about using common sense when it comes to working on cars. However, I get away with more stuff now cause its not a junky ricer

Im just concerned about how fast that battery just drains with just a little bit of draw on it. Maybe ill invest in that load tester could come in Handy...

 

[Big_John]

I keep wanting to tell you to just disconnect the battery, but I know you live in an apartment complex. I understand the want and need for the alarm system.

Just spit balling here.... What about using a separate battery for your security system. Maybe a small lawn tractor or motorcycle battery. Then you could just disconnect your starting battery.

There would have to be a couple things worked out... I'll bet you could use the solar charger to keep that battery topped off. It would take some thought to make sure all the systems work together, but I think it could be done.

 

[Knebel]

I wish I could just disconnect. But the security system came in handy before, it's fun chasing people away with a bat at midnight when they rattle on the doors lol. You would not believe how fast I am out there when the key fob starts beeping.

They make a "backup" battery for the system, maybe that's something to look into but I believe that feeds off of the starter battery too. The thing is, the battery still drains with the security system disconnected. It even happened without the EFI before. Maybe interstate just makes crappy batteries?

 

[Big_John]

I wish I could just disconnect. But the security system came in handy before, it's fun chasing people away with a bat at midnight when they rattle on the doors lol. You would not believe how fast I am out there when the key fob starts beeping.

They make a "backup" battery for the system, maybe that's something to look into but I believe that feeds off of the starter battery too. The thing is, the battery still drains with the security system disconnected. It even happened without the EFI before. Maybe interstate just makes crappy batteries?

The battery for the security system would be a separate system all together. No interconnection with the starting battery for the power for the security system.