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Help with wires going to POS battery post and drain on it

Tried to start my car (87 Targa) after a week sitting and the battery was completely dead. Put a charger on it and never would get past 41%. Tried to jump it and the clip was too large on the cables and as I was moving it to get a good connection, broke off a wire connected to it (see pic below). It broke off pretty easily and when I touched the wire to the pos post it sizzled a bit.

The only change I made to the car is installation of the F9 DME and the car ran fine after that.

Iím going to get the battery checked but two questions:

1.) Where can I find in the manual what these wires go to?
2.) Is there any possible reason the DME would cause a drain on the battery?

Thanks in advance for any thoughts.




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1987 911 Carrera Targa
Old 04-10-2020, 07:32 PM
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One suggestion on the battery drain is to check your door dome light switches. After you have turned the car off at the end of a journey, the power windows and seats stay active until a door is opened and the light switches on (at least in my 86 - I don't know about earlier models.) One of my door switches hangs up in cold weather, and if I don't open the other door, or remember to pull the switch out with my fingers, the battery drains much quicker than when the light comes on when leaving the car. I have a 7 year old battery, and it's good for three week naps between drives, unless I was forgetful about the dome light. Soon, I'll pull the switch out and fix it, but at least I know the source of my problem.
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Old 04-10-2020, 08:16 PM
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one of my favorite drains that took a while to figure out was the frunk light that has a micro switch..it kept NOT going off and drained the battery a few times til i figured it out
Old 04-11-2020, 03:56 AM
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If you have a VOM you can check current draw on each of those leads, basic meters can be had for cheap. How old is the battery?
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Old 04-11-2020, 05:07 AM
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Charge the battery and disconnect suspects get a meter and see if there’s a draw off battery. Could be a number of things from lights to alternator et. Use process of elimination along with a meter.
Old 04-11-2020, 05:11 AM
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This is a pretty good outline on how to find parasitic battery drains:

https://www.wikihow.com/Find-a-Parasitic-Battery-Drain
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Old 04-11-2020, 05:55 AM
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Quote:
Originally Posted by RedCoupe View Post
One suggestion on the battery drain is to check your door dome light switches. After you have turned the car off at the end of a journey, the power windows and seats stay active until a door is opened and the light switches on (at least in my 86 - I don't know about earlier models.) One of my door switches hangs up in cold weather, and if I don't open the other door, or remember to pull the switch out with my fingers, the battery drains much quicker than when the light comes on when leaving the car. I have a 7 year old battery, and it's good for three week naps between drives, unless I was forgetful about the dome light. Soon, I'll pull the switch out and fix it, but at least I know the source of my problem.
^This^--easy first step to check/rule out --

Re your other questions

1) don't believe the DME relay's activated until the ignition's switched on, so (unless I'm wrong) don't see how the relay could cause the battery to drain

2) no clue what the red wire goes to, but should be easy to re-terminate and crimp back on -- here's a link to a kit that looks like it'll have what you need - see https://www.amazon.com/120-Wirefy-Heat-Shrink-Connector/dp/B01N1WWR7E/ref=sr_1_3?dchild=1&keywords=crimp+connector+round+end&qid=1586616710&sr=8-3

any idea how old your battery is? Given that it won't take a charge, it could have simply failed. Regardless, sounds like it needs replacement -- recommend you consider downsizing to a Group 48 battery and getting an AGM style battery -- see Need a new Battery for my 911


let us know what you find out.

Last edited by darrin; 04-11-2020 at 07:57 AM..
Old 04-11-2020, 07:48 AM
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When I recently installed my Odyssey battery, before I tightened everything down on the Rennline battery mount, I pushed the positive/negative terminals on to check it, and it wouldn't start. I didn't connect all of the wires to the positive terminal at that point, since I just wanted to check it first. I thought maybe the Odyssey was bad, so I checked it with a voltmeter and it was fine. I connected all of the wires to the positive terminal (big power wire, battery tender, headlight relay, and "mystery wire") and it started and everything was perfect. I think my "mystery wire" is the one in your pic that isn't connected, and looks like it came out of the same loom. I would re-terminate that wire and connect it, and I'd bet that fixes it.

A 41% charge on your battery should at least turn the starter over, if not start it. Those percentages on the charger don't mean much anyway, and your battery might be okay. It's possible that the wire in question was making a bad connection prior if it broke off that easily.
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Old 04-11-2020, 09:12 AM
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Well, thanks to everyone for replying. Took a few days but here's what I did:

- Battery was completely dead. No power. Nothing could bring it back to life so got free swap out (since only a year old)
- Charged it, installed and put tender on it.
- NO lights, locks, windows, etc. left on
- Car ran great.
- Started to look for power drains and happened to be in the engine bay after a drive to just see if anything leaking and heard a buzzing noise.

Power Drain = Fuel Pump is constantly on. The week before, had installed the F9 Pump Prime Relay just because I had it and low and behold that is the issue. So put the old one back in and everything good.

So - begs the question - why is this constantly on when the key is out of the ignition? Thoughts?
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Last edited by speedracer92; 04-14-2020 at 06:42 PM..
Old 04-14-2020, 06:36 PM
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make sure your pump is still good..i thought it was bad for them to run without fuel moving through?
Old 04-15-2020, 03:34 AM
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Quote:
Originally Posted by speedracer92 View Post
Well, thanks to everyone for replying. Took a few days but here's what I did:

- Battery was completely dead. No power. Nothing could bring it back to life so got free swap out (since only a year old)
- Charged it, installed and put tender on it.
- NO lights, locks, windows, etc. left on
- Car ran great.
- Started to look for power drains and happened to be in the engine bay after a drive to just see if anything leaking and heard a buzzing noise.

Power Drain = Fuel Pump is constantly on. The week before, had installed the F9 Pump Prime Relay just because I had it and low and behold that is the issue. So put the old one back in and everything good.

So - begs the question - why is this constantly on when the key is out of the ignition? Thoughts?
Those fuel pump relays are a hit or miss. I installed two new ones in my 930 and the pumps were cutting off during my drive. I put the old ones back and the symptoms went away.
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Old 04-15-2020, 05:49 AM
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Originally Posted by 7783911 View Post
make sure your pump is still good..i thought it was bad for them to run without fuel moving through?
Hmm, that's a good point. I think its ok because it basically sat running the garage for a week which killed my battery. When I replaced the battery went on a cruise and then another one 1 day later and no issues. So hoping its ok.
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Old 04-15-2020, 05:03 PM
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Quote:
Those fuel pump relays are a hit or miss. I installed two new ones in my 930 and the pumps were cutting off during my drive. I put the old ones back and the symptoms went away.
Well, the Mfg going to send me a replacement (super happy with their customer service) and also gave me some instructions on how to avoid possible ESD (Electro-Static Discharge) which can happen during installation:

1. Keep the relay in the anti-static bag.
2. Remove the original relay from under the driver seat.
3. Touch the body of your Porsche, preferably exposed metal.
4. Remove the Solid-State Relay from the anti-static bag
a. Avoid touching the pins if at all possible
b. Maintain physical contact with your Porsche if at all possible.
5. Install the Solid-State Relay

Will report back once I receive and install.
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Old 04-15-2020, 05:04 PM
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Originally Posted by speedracer92 View Post
1. Keep the relay in the anti-static bag.
2. Remove the original relay from under the driver seat.
3. Touch the body of your Porsche, preferably exposed metal.
4. Remove the Solid-State Relay from the anti-static bag
a. Avoid touching the pins if at all possible
b. Maintain physical contact with your Porsche if at all possible.
5. Install the Solid-State Relay
Laughable, that such an automotive part like that is being sold to consumers, and with poor reliability.
Once the original OEM part is re-soldered (10 minutes), the part is more reliable than new.
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Old 04-15-2020, 06:19 PM
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So, installed the replacement F9 SSR. As a reminder, this one has the Pump-Prime feature automatically runs the fuel pump for up to 3 seconds when the ignition is switched to the "On" position. Week later, battery completely dead again - like so dead it will never come back which is indicative of power going to the relay I installed and it basically priming the pump or something until all juice is out of the battery.

I've never had this issue with my OEM Relay and while I know that I can just install it and leave well enough alone, the cats out of the bag and there MUST be power going to the Relay even when the ignition is off and key is out. Nothing else is on in the car and again, with the original one, never had an issue with the battery.

Any thoughts on what could be happening here? I don't think the F9 is the cause of the power just reacting to it and draining the battery.

TIA...Todd
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Old 05-04-2020, 07:33 AM
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Todd:

take a look at the wiring schematic at the following link -- https://dorkiphus.net/porsche/showthread.php?t=16859

specifically, note how the dme relay completes the circuit between pin 30 "+12 volt from battery unfused" and pin 87b "+12 volt to fuel pump via fuse 3"

this suggests to me that the f9 IS the source of your always running fuel pump, as the same result would occur if you simply inserted a jumper wire between pins 30 and 87b
Old 05-04-2020, 09:21 AM
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Quote:
Originally Posted by darrin View Post
Todd:

take a look at the wiring schematic at the following link -- https://dorkiphus.net/porsche/showthread.php?t=16859

specifically, note how the dme relay completes the circuit between pin 30 "+12 volt from battery unfused" and pin 87b "+12 volt to fuel pump via fuse 3"

this suggests to me that the f9 IS the source of your always running fuel pump, as the same result would occur if you simply inserted a jumper wire between pins 30 and 87b
Thanks. Great post you linked to. I definitely think the SSR is the cause of the fuel pump running, but what I don't understand is that no power should be going to the SSR at all when the ignition is off, correct? So, the SSR will cause the pump to go until the battery dies, but it shouldn't.

From the MFG --> With the key in the off position the Pump-Prime feature is electrically disabled and cannot allow current to flow to the fuel pump. With the ignition off, the Solid-State relay is designed to not draw or provide current.


This is the second one - so something has to be wired wrong in my car. But even with the OEM DME, power would be going to it, but since it doesn't have pump prime, nothing is powered with it?
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Old 05-04-2020, 07:51 PM
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Originally Posted by speedracer92 View Post
Thanks. Great post you linked to. I definitely think the SSR is the cause of the fuel pump running, but what I don't understand is that no power should be going to the SSR at all when the ignition is off, correct? So, the SSR will cause the pump to go until the battery dies, but it shouldn't.

From the MFG --> With the key in the off position the Pump-Prime feature is electrically disabled and cannot allow current to flow to the fuel pump. With the ignition off, the Solid-State relay is designed to not draw or provide current.


This is the second one - so something has to be wired wrong in my car. But even with the OEM DME, power would be going to it, but since it doesn't have pump prime, nothing is powered with it?
Personally think this is solely being caused by the electronic relay -- I'd try substituting in a standard electrical relay and see if the problem persists.
Old 05-04-2020, 08:26 PM
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Personally think this is solely being caused by the electronic relay -- I'd try substituting in a standard electrical relay and see if the problem persists.

Thanks. Battery does not get drained with the OEM relay. However, there are over 1000 of these supposedly installed in vintage Porscheís with no issue, so just trying to figure out what about mine is not correct - something has to be in the wiring.
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Old 05-04-2020, 08:28 PM
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So, latest update. Replaced completely dead battery for second time (Interstate said last time they will swap for me for free), put OEM relay back in and and then systematically went through each fuse, pulling it to see when the battery went to 1mA. Right side parking light showed drain. Jacked with it for hour and could never figure out why i twas behaving this way until I called my Porsche Mechanic friend who told me to go check my turn signal and sure enough it was engaged. Even though key is out and ignition off, I guess it will turn it on. Makes no sense because I would have noticed lights being on the past two times - am sure of it, but regardless, that seems to be the issue this time. So, I am checking each night and battery is holding at 12.7+- Volts. So far, 2 nights and its fine. I will do this for a week, then going to put the Pump Prime SSR back in and do the same thing - check each night as it sits. No charger is on it while I test. Will report back after two weeks. Seems odd, but guess that could be the culprit.

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Old 05-11-2020, 04:52 PM
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