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Old 09-23-2018, 02:04 PM   #1
texas_snake
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Battery to power distribution voltage drop issue

I have been working out the kinks on my 03 Mach 1 since buying a couple months back. Been chasing a voltage issue many accessories are running (lights and A/C mostly). I noticed over time the positive battery to power distro box is heating up and having voltage drop over time when running with the extra's on. Over time drop can be big (.75 volts or more) so I am checking into cleaning main grounds.

But one thing has stood out. The yellow positive connection is on my positive battery post. Looking at stock mach 1 engine pics, it looks to connect to the power distro block along with a smaller connection off the positive battery cable. So the question is, do I have to have 2 connections on the power distro box (yellow from harness and red from positive battery) and just one going to the positive battery? It is 1 red to power distro box and 2 - yellow and red to the positive battery now.

I have suspected this for a while, but now that I see voltage drop there with heating when loading the system, I really need to know if this matters or not.

I would switch it, but the power distro box threads are messed up and that nut wont come off easily and I don't want to damage the fuse box, but will give it a try to move it if that is required.

Thanks!
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Old 09-23-2018, 08:31 PM   #2
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Re: Battery to power distribution voltage drop issue

Sounds kinda like the diodes went bad in your alternator putting out ac voltage
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Old 09-23-2018, 10:28 PM   #3
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Re: Battery to power distribution voltage drop issue

Yeah, I checked that. It is putting over 14 volts to the positive battery post. Positive and negative voltage drop is normal from the Alt. Also the negative voltage drop is the same on the Alt to negative battery post as it is to the block to negative battery post, so Alt is grounded well.

It seems to be in the hop from the positive battery post to the dist box (large voltage drop and heating wire) and I suspect that yellow tipped connection should be on the power distribution block and not the positive battery post.

Can anyone confirm that theirs has the yellow tip going to the power dist block?

Further, does anyone know what that yellow tipped connection is?

Thanks.
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Old 09-24-2018, 02:30 PM   #4
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Re: Battery to power distribution voltage drop issue

Can someone take a picture of the positive battery post and power distribution block connections. And a second with the cover lifted on the power dist block showing those connections. I really need to see how this is wired. I think mine has been wrong since I got the car.

Thanks.
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Old 09-24-2018, 03:03 PM   #5
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Re: Battery to power distribution voltage drop issue

Just sent you a message. Be glad to help if I can.
Scott
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Old 09-24-2018, 06:31 PM   #6
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Re: Battery to power distribution voltage drop issue

OK. Scott helped me out today with some pics and it is clear the yellow tip wire should be on the power dist box (fuse box) and mine is on the positive battery post. So 2 connections on power dist box and just one going to the battery (with a jumper to the power dist box).

Need to move it and see how things work. But that nut is cranked on there and the box is a bit fragile. Will do my best to make this work.

Will report back later on if this addressed my power issue when under heavy load (voltage drop at the fuse box). I truly think it will.
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Old 09-25-2018, 08:06 AM   #7
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Re: Battery to power distribution voltage drop issue

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Originally Posted by texas_snake View Post
OK. Scott helped me out today with some pics and it is clear the yellow tip wire should be on the power dist box (fuse box) and mine is on the positive battery post. So 2 connections on power dist box and just one going to the battery (with a jumper to the power dist box).

Need to move it and see how things work. But that nut is cranked on there and the box is a bit fragile. Will do my best to make this work.

Will report back later on if this addressed my power issue when under heavy load (voltage drop at the fuse box). I truly think it will.
Hope it works for you good luck.
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Old 09-25-2018, 03:07 PM   #8
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Re: Battery to power distribution voltage drop issue

OK, I admit it was scary as I thought I might end up ripping off the bolt on the power distribution block trying to get that nut off. But with some help and special tools I was able to get it off OK.

I found the reason the dumb-a$$ before me didn't put the Alt connection on the power distribution box (fuse box) is they replaced the end on it (had broken off on the bolt on the fuse box (found the broken piece) and put a small tip on it and it did not fit on the fuse box bolt, so they added it to the positive battery post. IT DOES NOT BELONG THERE! The smaller red wire going from the positive battery post to the fuse box will overheat with too many accessories on and they you start hitting big voltage drop to the entire car.

After some time my PCM hit below 12 volts and the car would act up (instrument gauges reset while driving, lights flicker, etc).

This was the fix to all of that. I can see with Forscan the PCM is now healthy on vpwr (over 12 volts with load to the pcm always). Alt is good (better than my 03 Cobra as I compared them).

So bottom line, the 2 grey wires, which are from the Alt, MUST GO TO THE FUSE BOX.

Hopefully this helps the next guy if they see this thread. As I stated, I have been working the shade tree mechanic out of this car (3 prior owners). Almost done. It is turning into a great/fun car.
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Old 09-25-2018, 03:51 PM   #9
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Re: Battery to power distribution voltage drop issue

glad that took care of it!
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Old 09-26-2018, 08:16 AM   #10
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Re: Battery to power distribution voltage drop issue

I could totally see a DIY'er doing what you've explained. The fact they didn't take a ride to AutoZone to get a proper size end for the alt wire shows they aren't even worthy of backyard mechanic status, maybe just a hack..
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Old 09-26-2018, 03:36 PM   #11
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Re: Battery to power distribution voltage drop issue

yeah, could just be either lazy or clueless work.

I found another ridiculous mistake on the car. I saw a blue injector on cyl #6 which is odd as we use 24 lb green injectors on the mach 1 (my 03 Cobra uses the blue). Checked the part # and sure enough, it was from a Cobra. It was a 39 lb injector mixed in with our stock 24 lb green injectors. I was seeing driver side O2 sensor readings as rich with Bluedriver obd 2 scanner and that was the reason why. Could not believe that hack. Replaced it right away. I am looking over every inch of the car as it is clear I can't trust any of the prior work. I am about done though. Had to bring the car back to the quality it deserves as a limited edition. Love the car.
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Old 09-26-2018, 04:44 PM   #12
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Re: Battery to power distribution voltage drop issue

Quote:
Originally Posted by texas_snake View Post
yeah, could just be either lazy or clueless work.

I found another ridiculous mistake on the car. I saw a blue injector on cyl #6 which is odd as we use 24 lb green injectors on the mach 1 (my 03 Cobra uses the blue). Checked the part # and sure enough, it was from a Cobra. It was a 39 lb injector mixed in with our stock 24 lb green injectors. I was seeing driver side O2 sensor readings as rich with Bluedriver obd 2 scanner and that was the reason why. Could not believe that hack. Replaced it right away. I am looking over every inch of the car as it is clear I can't trust any of the prior work. I am about done though. Had to bring the car back to the quality it deserves as a limited edition. Love the car.
good lord man... hopefully theres not too much more to be found
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Old 09-27-2018, 12:25 AM   #13
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Re: Battery to power distribution voltage drop issue

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Originally Posted by texas_snake View Post
we use 24 lb green injectors on the mach 1
The stock injectors from my car are black..
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Old 09-27-2018, 11:46 AM   #14
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Re: Battery to power distribution voltage drop issue

There should be a very small part number on them on the side (might have 2 different numbers on each side). Try googling them and see what turns up. Aftermarket injectors might come in different colors. But from what I saw when checking into it, many try to stick to ford colors. The colors might change based on model (ev*), but we should be EV6.

So likely they are 24 lb injectors that were replaced with aftermarket. I believe Bosche was the original maker.
Here is a good link on mustang injectors.

https://lmr.com/products/mustang-fue...tor-size-chart
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Old 09-27-2018, 01:32 PM   #15
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Re: Battery to power distribution voltage drop issue

Quote:
Originally Posted by texas_snake View Post
There should be a very small part number on them on the side (might have 2 different numbers on each side). Try googling them and see what turns up. Aftermarket injectors might come in different colors. But from what I saw when checking into it, many try to stick to ford colors. The colors might change based on model (ev*), but we should be EV6.

So likely they are 24 lb injectors that were replaced with aftermarket. I believe Bosche was the original maker.
Here is a good link on mustang injectors.

https://lmr.com/products/mustang-fue...tor-size-chart
Just making sure the rest of your injectors weren't wrong too. The factory set is definitely black, so when you said green and were already dealing with mismatched stuff...well..it just doesn't make too much sense to swap factory injectors with aftermarket ones that are supposed to be the same size. But who knows what the po was thinking.
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Old 09-28-2018, 12:18 PM   #16
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Re: Battery to power distribution voltage drop issue

So mine are all green (darker green) and the new one I got to replace the Cobra injector is light green by Bosche (vs Ford part). So perhaps they have all been replaced then if they come black stock. I guess that is a bonus for me.

I will double check the numbers on the side of them (think I did when I found this issue, but will do it again for certainty they are 24 lbs). Thanks for the info.
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Old 09-28-2018, 03:47 PM   #17
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Re: Battery to power distribution voltage drop issue

Quote:
Originally Posted by texas_snake View Post
So mine are all green (darker green) and the new one I got to replace the Cobra injector is light green by Bosche (vs Ford part). So perhaps they have all been replaced then if they come black stock. I guess that is a bonus for me.

I will double check the numbers on the side of them (think I did when I found this issue, but will do it again for certainty they are 24 lbs). Thanks for the info.
No problem. If you decide you need a set of originals I've got some sitting here.
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