EEC circuit draws current w/ignition off

[benwood]

In trying to determine why my battery kept dying, I discovered that my EEC circuit is drawing 0.6 amps. Here's the symptoms:

1) disconnect battery & remove hood lamp; insert ammeter (completing circuit): 0.0 amps current draw
2) turn ignition on, ammeter says ~ 7 amps
3) turn ignition off, ammeter now says 0.6 amps, and it says that way indefinitely.

When I disconnect/reconnect my ammeter (across the battery terminals), I can hear something actuate, but not sure what. In checking all the fuses and relays, I narrowed it down to the EEC relay. Pull out, ammeter goes to 0.0; push back in, ammeter goes to 0.6 and I hear something activate near the center of the engine.

I noticed that I had two identical relays under the hood matching the EEC relay, so switched them, same result. So the relay appears to be good.

Not sure where to proceed next. I'm pretty sure the EEC circuit should be OFF when the key is out...

Thanks for any ideas or pointers!

--Ben

1991 Mazda Navajo, 98k miles.

 

[Michiganbear]

the EEC will ALWAYS draw power when the battery is connected. Just HOW much I dont know.

the EEC has to keep its memory alive (for not only the stored trouble codes, but also the learned parameters), so there will always be a current draw.

there may be other circuits drawing too.. radio/clock have memories.. remote/keyless entry (memory and monitoring of the keypad/remotes).. and probably some others too.

to be honest, 7 amps seems low to me, but then the fuel pump wasn't running, and since engine wasn't running, the injectors/coils/ect wasn't powered up.

 

[benwood]

Thanks for the input. I could imagine that the EEC would always draw, unless codes are in firmware ?? In any event, the reason I've been troubleshooting is that my battery keeps running down. The old one was ruined in 2 years from deep cycling, and the one in there now is brand new, yet died in just 3 weeks. This vehicle is sometimes only driven once a week.

When I connect the battery, I can hear something engage (sort of a click and whirr for about 1.5 seconds), and there was much more sparking than I've ever seen with a battery connect before. 0.6 amps is 7.5 watts, which works out to 100 amp-hrs/week.

My advanced battery charger from Sears also will take a stab at one's alternator, and it claimed the alt. was running 100% (across battery terminals). That, and the instrument reading for the alternator seem to rule out the alternator. The component activation noise on battery connect seems wrong to me -- I don't recall that before on any vehicle. But I'm just a weekend hack.

My Navajo is old -- no remote entry or remote start. I think the fuel pump does activate when the ignition is "on" but not positive. By the time I get around to see my multimeter, the pump would be fully pressurized.

My only lead so far is that the EEC circuit draws 0.6 amps with the ignition off, and disconnect/reconnect causes something near the center of the engine to power up (or charge up?). That, and the battery going out after just a few weeks. I'd think a normal vehicle could be parked for six to eight weeks easily without a battery fully discharging.

the EEC will ALWAYS draw power when the battery is connected. Just HOW much I dont know.

the EEC has to keep its memory alive (for not only the stored trouble codes, but also the learned parameters), so there will always be a current draw.

there may be other circuits drawing too.. radio/clock have memories.. remote/keyless entry (memory and monitoring of the keypad/remotes).. and probably some others too.

to be honest, 7 amps seems low to me, but then the fuel pump wasn't running, and since engine wasn't running, the injectors/coils/ect wasn't powered up.

 

[mikeinri]

I don't know any specifics that will help you, but I can leave my 94 Explorer sitting for a month in subfreezing temperatures and it starts right up every time, with no signs of battery weakness. So, I'd agree that you definitely have an issue.

Mike

 

[Michiganbear]

the most common cause of battery drain is a bad diode or 2 in the alt. Note: even with a couple bad diodes, the alt will still charge the battery!! BUT, it will also cause early battery death as well.

another thing to look for would be corrosion someplace. not only does it hinder proper charging and such at the battery, it can cause a leakage current to flow.

these kind of electrical problems are tough to diagnose, thats for sure.

I would go check some things on my 92 explorer for ya, except for one thing.. my exploder is missing 1/3 of its fuel line, and I dont want to take a chance right now of dumping a bunch of fuel out of the tank, or causing a 'boom'. I hope to fix it this weekend, and if I do, I will see what I can find out on mine to help point you in the right direction

 

[benwood]

Initially I expected to find a short of some sort, but the constant drain and the activation of some unit under the hood when attaching the battery cable makes me think there's something else going on.

I've thought about the computer memory issue. A standard desktop PC has memory (BIOS settings) that is backed up by a tiny watch-type battery typically for four years. In other words, the current draw by the computer when the ignition is off is likely extremely small.

I'd be curious what you hear when you attach your battery again. I can't be sure, but I don't think I've ever heard anything before except a slight spark (clock/radio).

Thanks for thinking about this, and I hope more theories float along. These are just the sort of lame repairs that cost hundreds at a shop!

the most common cause of battery drain is a bad diode or 2 in the alt. Note: even with a couple bad diodes, the alt will still charge the battery!! BUT, it will also cause early battery death as well.

another thing to look for would be corrosion someplace. not only does it hinder proper charging and such at the battery, it can cause a leakage current to flow.

these kind of electrical problems are tough to diagnose, thats for sure.

I would go check some things on my 92 explorer for ya, except for one thing.. my exploder is missing 1/3 of its fuel line, and I dont want to take a chance right now of dumping a bunch of fuel out of the tank, or causing a 'boom'. I hope to fix it this weekend, and if I do, I will see what I can find out on mine to help point you in the right direction

 

[Michiganbear]

well, the computer CMOS battery analogy kinda works, but the amount of data (and therefore the size of the NVRAM) is hugely different. Most cmos settings are saved in a measly 1 or 2k (thats the largest CMOS ram I have ever seen in a pc). The data saved in the EEC is probably on the order of 32k or more. Also, the technology used in the keep alive memory is different than the CMOS memory in the pc.

the keep alive memory is nothing more than static ram, not specialized for low current consumption, as the CMOS ram in pc's are. Also, the ram in the EEC does NOT run at 12v, but 5V most likely, and the voltage regulators used in them are of a very old (but durable) design, and not very effecient either (lot of wasted power).

Yes, the EEC is likely turning on a relay or solenoid on power up. and that relay may be required to be pulled in (active) when ever the EEC has power.

Until I can get my 92's fuel system intact, and can mess with the stuff as you are, I can't give much more info.

Also, if needed, I can maybe get my service cd installed on my new pc and look at the wiring diagram some and see what is possibly happening

Just as a reference, on my 91 Continental, when I connected the battery, I would ALWAYS get a hell of a spark. but it would sit literally for months and not loose the battery. It had no less than 4 computers in it all starting up, plus the clock, the radio (seperate on this car), and probably even the EATC (Electronic Automatci Temp Control, although I dont remember for certain if it had a constant 12v feed)

 

[benwood]

Thanks for all your thoughts, MB. I'd appreciate any wiring info if you have time. Yes, if it's static RAM, it would have more current draw, definitely. Static is probably more robust for an auto environment. The 12v/0.6a draw of 7.2 watts would mean about 1.5a @ 5.0v (after step-down). Seems high relative to how much capacity batteries typically have (for a sustained parked auto condition). If the reserve is say 90 minutes @ 25 amps, then if it were a linear matter, that would be 62.5 hrs @ 0.6a. Assuming (as a guess) that the reserve at such a slow draw would be 50% higher, then that's just ~96 hours before the car won't start again. That is within an order of magnitude of what I'm seeing, having a problem if it's been > 1 week.

I pulled the EEC relay and reconnected my battery -- some spark, but the 'whatever' under the hood was silent. Plugging in the EEC relay at this point did nothing and current draw remained too low to read on my 10a scale. However, after turning the ignition on, then off, the 0.6a draw was back. And pulling and reinserting the EEC relay at this point caused the 'click-whirrrr' and the 0.6a resumed.

If the EEC relay is independent of the computer circuit, then my pulling the EEC relay rules out the computer since the ammeter reads near zero at that time.

So... mystery continues. I'll see if I can did up more information, too, although so far I've whiffed. I do appreciate your thoughts and input immensely. I wish my manual were of more help!! I'll have to read other sections to see if I can get a clue.

One thing that is bugging me is the relay itself. I did switch with another, with no change in the situation. It bugs me because the fuel pump relay failed a few years ago, and the result was similar, with the pump being activated continuously, even with the ignition off. That is akin to what I seem to be seeing. Maybe my test was faulty... I can get a new relay for a few bucks to positively rule out the relay at least.

 

[benwood]

I have another thought... maybe I am confused about what the EEC relay actually is?? There's a fuse box behind the battery along the passenger side of engine compartment. I thought the fuse links in there were the relays -- they are marked 30A, 15A etc. -- like giant 'under dash' fuses. However... maybe those are just fuses and the relays are elsewhere? If that's true, then perhaps the relay is stuck closed and is actually under (?) the fuse. I'll have to take another look and gander at my Haynes manual which I think doesn't have any photos to match for that area.

I'm not positive there's actually an EEC Relay but I believe so...

 

[solitary ogre]

i'd suggest a wiggle test of all the wires in and around the engine compartment. watch your meter as you do the wiggle test and see if it changes any. make sure you move the wires enough to ensure there isn't a problem with them but not enough to create new problems.
if that didn't show anything then i'd be tempted to pull apart the ignition switch in the steering column to see if there is something making contact when the key is removed. it is a sliding type switch making several contacts depending on the position the key is in.... "acc" "off" "on" "start" "eject" (only on some models)

good luck, i'm curious to find out what your problem is.

 

[benwood]

Thanks for the ideas. I should have some time to fiddle with it this weekend. Wiggling can be useful. And I think there is a chance that it is the ignition switch, based on how that 'turns on' the battery leak.

After more study of my Haynes manual and some googling, I did figure out that there is an EEC Power Relay under the box that contains the engine compartment fuses (behind the battery, along the fender). From what I can tell, this is the exact same relay as the fuel pump relay. I must have been under there before (pull up the panel to access) because I replaced that fuel pump relay before... that was 9 years ago. At least I remembered the area under the hood, but didn't remember the "under" part.

From my study of the wiring diagrams in the Haynes manual, it appears that power to one input of the relay is always ON and that a signal from the ignition must also go on to close the relay and thus power the computer (more of an electronic ignition module for that era).

So... the relay is probably remaining tripped, and the current leakage I've observed may therefore be the EEC module continuing to remain active.

And if that's all correct, then either the relay is faulty, or the ignition switch is faulty by continuing to signal that the ignition is in the START or RUN position. Seems like there should be a way to figure out which is it, assuming this working theory has any bearing on the battery drain problem...

I think if I can access the ECC relay, I can use my voltmeter to determine how it operates and verify that the ignition signal goes ON then back OFF. If it doesn't go OFF, that's probably the bad switch. IF it does go off, however, but the switch stays closed (that is, output is still 5v) then the ECC Power Relay is probably bad.

I'm typing this all out partly to think it through. Seems logical at this point. And... it could all be a red herring!!

 

[solitary ogre]

how much current is required to operate the coil on the the relay?
0.6 amps?
just curious.
with a little more fiddle farting around you'll be sure to fix it.

 

[benwood]

I replaced the EEC power relay this weekend (cost just $15) but I could not confirm that this solved the problem because fiddling with the wires and connector caused the problem to go away (during my testing at least).

The measurments I made:

ignition OFF:
Y wire: 12v (<-- battery)
R/LG wire: 0v (<-- ignition switch)
R wire: 0v: (--> to EEC)
BK/W wire: 0v (--> ground)

ignition ON:
Y wire: 12v (<-- battery)
R/LG wire: 12v (<-- ignition switch)
R wire: 12v (--> to EEC)
BK/W wire: 0v (--> ground)

And with ignition returned to OFF: same as initial conditions (and confirmed 0.0a drawn on battery). Before I had 0.6a draw when I returned to the OFF state, but my handling the relay and harness apparently changed this. If I'd have been more diligent, I'd have checked for the current draw before unplugging/replugging the relay, which may have jostled it like a light bulb with a cracked but not broken off filament.

Thinking about this logically leads me to believe it was the EEC Relay switch sticking at the closed position, but not always. A failure of the ignition switch (being stuck closed) would result in the R/LG wire being hot when the ignition was off, and this was not observed. A cracked wire could prevent the car from starting but not make the switch fail.

Similarly, a wire problem on the R wire (to EEC) would keep the car from starting, but not make the switch fail. However, a faulty switch could produce what I observed. And it does seem reasonable that if the switch fails, the car can still run. When my identical fuel pump relay failed, the fuel pump was 'live' -- just all the time including when the car was parked.

The outlier possibility is that the ignition switch is the problem, but it simply did not fail this day due to temperature, humidity or ?? Only time will tell, but I replaced the more likely EEC Power relay (which users have posted elsewhere tends to fail ~ 70k miles, same as the identical fuel pump relay which for me did fail ~ 75k miles). I had the voltmeter on the ignition pin and used the key to wiggle the heck out of the switch but the meter stayed on 0.0v except when the ignition was ON, then 12v. I stressed it much more than before, yet not so much as a needle jerk on the voltmeter.

I think if I find the battery draining again, my next move will be to replace the ignition switch. But fingers crossed that I've taken care of the problem.

Thanks for the help and the ideas, and I'll post a follow up if warranted.

 

[Michiganbear]

well, there is a thought here..

there is a suppression diode inside the relay (to kill the induced spike when the relay is released). maybe it was leaky??

 

[benwood]

It sure would have helped if I could have 'caught' the thing either with the ignition relay wire hot or the output hot when the ignition was supposed to be (or actually) off. Whatever it was... it sure seems strange that it could have been intermittent. I could see something failing as it gets hot, say, but all my tests were when it was cold. Or perhaps it wasn't really cold in the first tests were I detected the leak, which itself may have kept the device hot enough for failure. The latter tests were done when I had the battery disconnected for a few days, which could be why it worked when I had the voltmeter out.

Too weird... I hope it's fixed now, though, what a pain! And pain for a car means a lot of dough if you don't figure it out.

BTW, my wife has a friend who's pickup used to have a battery drain problem. They didn't drive that truck much, so they just disconnected the battery when not in use. I guess that worked for them, although I'd worry about a short somewhere that would get worse.

 

[Michiganbear]

the vast majority of battery drains are stuck light switches (dome lite), leaky diodes in the alt (while it still will charge, one diode of the dozen or so it has can drain the battery when engine off), and of course my favorite one to rag people on..

left the headlights on..

 

[Tbars4]

...You should change your other 2 relays also...They get old and start to stick or become corroded...At about $10 bucks each, replacing them is good preventative maintenance...

...I had a simililar problem and it was my fuel pump relay, which is also very common and right next to the EEC relay..
http://www.explorerforum.com/forums/showthread.php?t=208097

 

[YBCold]

i have same problem. i pulled fuses coz i was havin .62 amp current drain. except my battery drained in a day or so. and its new, had my alternator bench tested and it tested good. ill post updates oh and i had the same underhood hum/ buzz when i reinserted my EEC Relay Fuse. im guessing thats the fuel pump maybe? but i think thats a different circuit.

 

[YBCold]

i have / had same problem. pulled out my EEC Relay and checked my alt wiring. and replace battery. seems to temporarily have fixed problem. i read zero current drain with battery off. when i turn the engine on (engine not running) i hear the elusive hum, probly the fuel pump. but nothing hums after turning the engine off.

BTW does anyone know where to get a replacement EEC relay? i cant find one.

 

[Not2]

eec relay / fuel pump relay

Hi all,
I joined your group just to say I have the same problem. This is a long post but hope this helps some. I've had my alternator rebuilt, as the vehicle has 145k and now 20 years old and others on the net said a diode could be bad. The brushes were worn down and bushings about worn out. Thought that fixed the problem then two weeks later dead battery again. I was working in the yard and heard my fuel pump spin up and then kick off after it pumped up to pressure. Gee, back to the net and see what others say, replaced the fuel pump relay, charged battery and two weeks later dead battery. Get out the meters and try to trace but this is an intermittant problem for me, no joy. A couple of days ago I used the truck and next morning dead battery. Charge battery, get out the amp meter and bam, intermittant problem is now active so I can gain some ground, I hear a big click and whirr noise when I hook up the amp meter and problem is not going away. I go get the wife to tap the amp meter while I figure out what is clicking. It's the Fuel pump relay that I relaced a month ago. I fiddle around where the EEC realy is located (and the fuel pump relay in my truck) and problem goes away. Back to intermittant state. Get out FORD manual and shows EEC relay controls fuel pump relay. I order Schematic book for 15.00 from Helm publications to get a bigger picture but go ahead and get new EEC relay from FORD (cost here was 30.00) now awaiting dead battery syndrome again. Next will be ign switch unless the schematic shows me something else. I hope this fixes my problem and hope this helps others as this seems to be a common problem. I'd change both relays out at the same time. Alternator may or may not be the problem, mine needed to be rebuilt anyway but didn't help the problem. Temperature didn't seem to be a problem except when it was cold, (I live just east of the Sierra's and gets cold in the winter) my truck which has two tanks sometimes (another intermittant problem) would switch but truck would die, no fuel transfer. That issue didn't come up last winter but exchanged it for dead battery syndrome. I suspect both relays to be at issue/Mike