Parasitic battery drain puzzler

[tripletdaddy]

I have a 95, 3.8 Taurus with EATC, analog instruments, auto headlights with delayed exit light turnoff, remote fob, keyless entry.

After enough puzzling and getting tired, I decided to clear my head, rest and hopefully have more collective thought from ya'll and hopefully shorten my troubleshooting.

I have a brand new battery and am loosing charge. Checked alt and then the underhood fuses. The "headlight" circuit was still active. Thinking disconnecting the headlight switch and the auto headlight switches would do it, I came to learn FIVE of the I/P fuse circuits are on the "headlight" main fuse. Continuing with my test light at the battery negative and clamp, I found one, no then two circuits at fault, depending on what order you pull them and reinstall them. I have yet figured out how fuse circuits 8 and 16 would be related to influence each other so that one disconnected but not the other will not open the drain. For example, the test light won't go off when I pull 8 alone, but will when I also pull 16. If I just pull 16, nothing happens until I pull 8 second. It's bizarre. I was hoping this would point me more quickly to my problem. I may have to ignore this phenomenon for now. Fuse 16 only has the EATC on it as I don't have the digital instr cluster. Fuse 8 has the courtesy/inside lights, radio memory, clock memory, keyless entry, power mirrors, illuminated entry module. TTBOMK, everything is working. I will have to double check if the problem doesn't get solved soon. Thanks.

[shorod]

Have you recently replaced the Digital Transmission Range Sensor? I seem to recall some time back another poster having an issue with the radio and EATC and it turned out to be a bad DTRS. I don't recall details though. I also seem to remember not being able to make sense of this since the DTRS didn't seem to be in the circuit for these components. I don't believe that poster had tried narrowing it down to a circuit or pair of circuits. Maybe try unplugging the DTRS and see if that has any effect on the current drain.

I also see that the instrument panel dimming rheostat is on instrument panel fuse #8. That would affect both the EATC as well as the radio, you may consider unplugging the headlight dimmer and seeing if that removes the parasitic draw. If not, then try pulling the radio and disconnecting the connector with circuit #8 in it to see if that fixes it, then the EATC.

You're right, there's nothing obvious to explain this one....

-Rod

[shorod]

As I looked further into the wiring diagrams, it appears circuit 8 only goes to dimming rheostat for the courtesy light portion and not for the illumination dimmer, so that wouldn't be a practical item to disconnect for troubleshooting.

-Rod

[tripletdaddy]

Uhhhhhh, a "digital" trs? Didn't know there was such an animal. I just thought there was a trs. Haven't changed it but will see what disconnecting will do. I can't make the connection though how it relates. I hadn't seen it in the diagrams, not to say I couldn't have missed it.

When I first investigated this, as I posted, all of the headlight stuff was and still is disconnected, so that would include the dimmer too. The dimmer is next to but not part of the auto headlight switch, but it controls both of the interior and dash lights. I thought disconnectiing the dimmer was practical as it was one of the easiest ones to disconnect! Yeh, I too see the two circuits aren't electrically connected and am not seeing anything that would join the two circuits in any of the diagrams. :banghead :screwy :runaround

Functionally, I haven't noticed anything not working, but I should more deeply investigate that. FWIW, I noticed that with the ke and the auto lamps, the kem takes the place of the iem. Could this be related to the replacement PCM? Could a dead digital clock do this? At this point, those things didn't appear to me to connect the two circuits, but at least the clock is part of one of the circuits.

FYI, this a station wagon.

[shorod]

Right, when I read about some of the past issues that were fixed by the DTRS/TRS I too didn't see a connection. Still don't. Some manuals call it the Digital TRS, others just the TRS. In this case, either are correct since there are discrete (digital) steps rather than continously variable (analog, like a TPS).

I wasn't sure from your first post if you disconnected all the headlight stuff or just discovered the additional circuits as you were looking at the diagrams for the headlight circuit. That rules one more circuit out then.

Help me out, what's the KEM and the IEM?

-Rod

[tripletdaddy]

Still no joy. .
I've eliminated the remote keyless entry module/illumination entry module, rkem/iem, the dead clock, and the interior lights as best as I can tell. I can't be 100% sure that I got all of the hidden lights if they are out since I can't see them! What hidden lights I remember are working. Suggestions where to look would be appreciated. I pulled the trs connector and even the connector next to it, which I guess is for the trans sensors and such, just to have no doubts. Maybe I'll even take a tire off if it will help!?!

So what remains to rule out on fuses 8 and 16 are the eatc, the pwr mirrors and radio memory.

[shorod]

I probably should have asked these questions sooner:

Did you replace the battery because it didn't hold a charge, or did this just happen after replacing the battery (ie: maybe you got a bad battery with a high internal resistance)?

Are you determining there's a draw because a test light in series with the battery glows, or are you using a current meter. If a meter, what is the current draw, and does the current draw drop after a minute or so? If a test light, can you get a current meter and post the current draw in amperes or milliamperes?

Just for fun, try disconnecting the alternator and re-checking the current draw.

When you're checking for current draw, you don't have a hoodlight that's on or a door open, do you? Can you verify the trunk and glovebox lights are not on?

It's not all that bad to disconnect the radio and EATC to determine if they are the source of the draw. You may want to unplug the radio and see what the draw goes to, but first I'd suggest knowing how much current draw you have.

-Rod

[tripletdaddy]

I'm going out there now to pull the eatc, radio and maybe the pwr windows. I already said in my first post that I eliminated the alt which I actually suspected in the first place. The battery was replaced as it would no longer hold a charge and it was quite old, so it's replacement was expected. I do not know if there was a parasitic drain prior to the battery replacement, but at least twice the new battery was down to nothing. I can recharge it to normal and it will hold a charge with the battery disconnected. How would I figure out if it is internally defective? By it's voltage?

Well, I thought I said it before, maybe not, but I am using a test light in series with the battery between the negative post and clamp. I think when I put my amp meter in place of the test lamp, I measure around half an amp. I'll have to check that again. No, no doors open, pulled hood bulb, glove box off, no trunk - it's a sw (boy you're loosing it), interior lights off. The test light glows about half bright. I did make the mistake of having a door or something on that had the light really bright and me stumped why so many power distr. fuses were involved. Was tired. Would it be meaningful to measure the voltage drop across the test light? I think it was around 9v with the battery 12.5 to 13v.

[shorod]

The voltage drop across the test light could be used to determine the current draw, but one would need to know the impedance of the test light to make the calculation. It seems easier to just use a current meter in place of the test light, although the test light is a better visual indication of when the draw goes away. It will be interesting to see what happens as you disconnect the EATC, radio, and possibly the power windows. If you find the radio is the problem, I have the one I removed from my 1993 SHO JBL system years ago. If you don't have the JBL system though, that may not do you any good as I don't believe it has an internal amplifier.

Oh, do you know if the car ever had an aftermarket alarm system installed? Conversations for these types of goofy electrical drains often start with, "Well, I was digging around under the dash and found someone had installed a Brand X alarm system and removed the fuse. Does anyone know where I could find an owner's manual for this?"

As far as losing it, yeah, I probably am. I've spent much of the day working with wood stain.

-Rod

[tripletdaddy]

So, if I measures the ohms of resistance of the test light and use I=V/R, I could calculate I and compare it to the measured I. Just to be sure, V is measured across the test lamp. I guess I could also calculate the current that is drawn by whatever is draining it by measuring the resistance of the drain and the voltage across it.

Well, I pulled everything that I know of on the suspect circuits. At first I thought I had it narrowed down to the radio at one connector as the test light dimmed at least by half. Nope, couldn't reproduce that later. ERRR. I eliminated the pwr mirrors (not the windows, they're not included) and all lights that I could find including out bulbs taking them out.

I was able to duplicate the bizarre electrical draw involving the two fuse circuits as I had described in first post. The EATC and the RKEM are somehow affecting each other. I was able to eliminate every single current draw. Without the EATC and the RKEM, the total remaining current draw is around 2 mA. Most of the time, the eatc and rkem draw around 6 mA. But, earlier, before I started pulling the connectors at the back of the radio and eatc to see which was the problem, when I would connect the meter at the battery, I would get current to start at 2 mA, I assume from the other normal current draws, and it would climb. It maxed out at 18 mA total or 16 mA I assume from the parasitic drain. How in the world are these two things interrelated? They're on different circuits and at opposite ends of the car?!?

I had previously completely disconnected the rkem/iem two modules with no change, but now realize that nothing would have happened since I also did not disconnect the eatc.

I don't think I need a new radio, but thanks for the offer. I think the FSM has mine with its own amp. TTBOMK, there isn't any security system. I'll look, but I've not seen anything that would make me think there is one. I sure do remember those folks with crazy electricals with those am systems. I'll check the wiring for splices and connections at the back of the ip. Any suggestions where to look and what it would look like?

Now I'm really annoyed with Ford's sm. I looked up the fuses and got their list of things on them, and they were severly incomplete!!! ERRRRRGGG!!! I had spent so much frickin time on the two suspect items thinking they were the last things and now looking at the pwr distr. dia there may well as be a million more things to check!?! Uuuuughh!!!!! Sighhhh. I think it would be easier to pull the fuses or the battery cable or charge it once a week at this point. I've got too much other s--t to do, and I'm too f--k n tired to fool around with this kind of s--t.

Well, I wanted to check things one more time before I posted this to see what kind of battery voltage remained overnight with the drain still there, and it didn't seem like it was drawn down much. I retested the amperage draw and used the test light, and it seems the problem may be gone for now. So I don't know what to do for now. I did measure up to 4 mA total draw, much lower than before. I don''t know what to do from here, and I don't want to get burned by this later.

[shorod]

Well, 18mA would not be a big draw. The threshhold is around 70 mA before you need to be concerned. You mention you think the current meter showed half an amp draw. If the problem comes back, try using the meter.

-Rod

[tripletdaddy]

I used both to measure the current. Right now, it seems to be ok. It is drawing 2 to 2.5 mA when letting it sit for the day or overnight. I wonder how much current draw there was to make the battery so weak it wouldn't start, maybe sitting for a week. I may have measured it once just below 10 v when wanting to start it. I just hate for this thing to strand me at a bad time unexpectedly.

[shorod]

Are you sure that your current meter scaling isn't off by a factor of 10? 2.5mA doesn't even seem like enough for the radio presets to be retained, and certainly not the radio AND PCM. Now 25 mA I could believe....

It almost has me curious enough to go measure the draw on my Mountaineer to see what it has for current draw. Someone once warned me about experimenting with my own vehicles in an attempt to help others out though.

-Rod

[tripletdaddy]

I'll measure it with two other meters, though I'm less confident in them than this one. It seems the problem has not surfaced for one day. Just before using the car today, I measured something really low, I think under 2 mA and the battery maintaned its voltage of 12.5 v, too. Previously, it would instantly bring it down 0.1 v from 12.5 v. I think it originally went below 10 v when left for at least a week.

When burning up your pcm......putting your meter on the battery, ONLY go between the neg post and removed neg clamp, not the neg post and the red post thingy. It'll toast your meter when your dead tired, nearly asleep. Just in case you stumble your way under your Mountaineer hood. Hmm, I warned you? Well, I don't think it's safe to experiment with it either, but measure it should be ok. Ok, now that I've warned you, what did you measure?

I'm gonna research more on what is a reasonable current draw. Oh yeah, I have a few more sacrificial vehicles that I can burn up.....test.....experiment..... measure. I'll report back with anything interesting. Thanks Rod.

[tripletdaddy]

If I hadn't stated it before, when there was a higher than expected amperage, it would start around 2mA and then would climb stopping around 10mA and maybe once at 18mA. This would take several minutes for it to level off. Any ideas why it's doing this?

If you have time, take a look at group 14 - battery and charge system in the FSM for 95 taurus. It provides some useful expected amperage draws. They say to use a test lamp, and if it glows, there is too much draw. Are they really talking about the typical automotive test lamp with a clamp on wire, sharp pointed tool with a neon lit handle? It's not what's in their diagram. Or, as in the picture, is it just an ordinary 12v bulb? What the heck is the shunt they suggest using and can I get one or make it or do I really need it? Is it a preset resistance that current goes through that you measure the voltage across it to give you the current? Why can't I do something like that without the shunt. When I measure between the neg post and neg clamp, it's about 11 v. If I then measure the resistance from the neg clamp to the pos clamp, can I use that info to calculate a meaningful amperage?