quint21

Hi guys,
I have a 1990 Toyota Pickup (140k miles, 3.0L V6 3VZ-E engine, brand new battery). With everything off, I'm showing around an 8 amp draw on my multimeter (set to 10A mode). Tried the test where I remove all the fuses one by one, but the draw persisted. If anyone has any ideas on what could be pulling around 8 amps let me know. I'm taking it in to a mechanic on Friday to have it checked.

After pulling/replacing all the fuses, I decided to try disconnecting the smaller wire coming from the positive terminal of the battery. This smaller wire goes from the positive terminal into a small black plastic box, with two terminals on it. The only thing printed on the box is "12V40A" and below that it says "050." As I was removing the rusty nut on on the of the terminals, the plastic cracked, and the terminal came off. Inside the box is what appears to be a reed switch of some kind. I need to replace this little black box, but I don't know what it is. The guy at the auto parts store couldn't figure it out either.

The 2nd terminal on the box is connected to a silvery canister-shaped component, with a bunch of wires coming out of it. I thought it was a starter relay, but googling 1990 Toyota pickup starter relay doesn't show anything that looks like it.

So, I would really appreciate any help in identifying the black box, the silver canister, or suggestions on what could be causing an 8A parasitic draw (that persists even after all fuses are pulled one by one). The draw persisted after the black box was removed too, for what it's worth.

Thank you in advance for any help!








The "mystery" box, 12V40A 050. Two terminals (one broken), reed switch inside. What is this thing?

I'm holding the black box close to where it lived, between the positive battery terminal and the silver can thing on the right.

Overview of the area, black box is removed.

scope103

Ah, the vintage parts quiz!
The small box with 12v40a is a 12 volt, 40amp, circuit breaker. https://www.wiringproducts.com/40-am...ght-angle.html DEFINITELY not stock. The hardware-store crimps on the wire are also a hint that it's not stock. I don't like such crimps, but compared to what I've seen in other Toyotas of this age, it looks like someone tried to do a good job.

The "silvery" cylinder is a relay, commonly used as a starter relay. I'm pretty sure your vintage truck has a stock starter relay, so this device has some other, unknown to me, purpose.

Draw with the fuses out could be caused by conductive "crud" somewhere before a fuse. Or, it could be due to something that isn't fused -- like the starter. (The starter is probably where I'd look next. More likely in the wiring than the starter itself, but who knows?)

Melrose 4r

8 amps is way of the charts. 50 milliamps is a good rule of thumb for modern cars with lots of electronics. First I would check your meter. correct position for leads, range, etc. Remember as my tech school teachers drilled into my brain, voltage across, current through!

The silver can is a Ford-style starter solenoid. It's somebody's attempt to modify the circuit to address the "click no crank" problem.

akwheeler

quint, let us know where you are, maybe someone in your area can stop by for a brew and have a look!
scope is spot on with the mystery items, breaker and a solenoid, follow the black wire from the right side in your picture and you will find what it is powering.
This is not a good sign when you are trying to find a draw, the previous owner (PO) did some hacking on the original wiring.
Pleas post a picture of your meter and how you have it hooked up so we can see if you have it wired right and set right to read current, not that we don't trust you... but it is hard to believe everything is turned off and you have an 8 amp draw and we don't know if you are experienced with a meter or maybe made a mistake.
Running through your fuse block with a test light will show you what still has power when the key is shut off and pulling those fuses should reduce or eliminate your draw thereby directing you to which circuit needs attention. Also try pulling the wires off of your alternator to see if the draw is there.

quint21

scope103, Melrose 4r, and akwheeler, thank you very much for your time, and your responses.

I really don't want to waste anyone's time chasing this down, but if you are curious, and at the very least want closure on this problem- I'll be sure to update when I find out what it is. I live just east of Spokane, WA, so if the mechanic is unable to figure out the issue on Friday, and anyone who happens to be local would like to share a brew with me over this- I'd welcome it.

Full disclosure: this is an RV, made by Winnebago. I didn't mention that in my first, because I thought it might be a red herring. My understanding is that the "house" (the RV living space side) is separated electrically from the truck. The "house battery" (a deep cycle battery) is not charged by the truck's alternator. And, the truck components (dome light, radio, etc) are not powered by the RV's house battery. Because I'm seeing the parasitic draw on the truck battery, I think the problem is probably on the truck side. But, I'm taking it to an RV mechanic, so hopefully he'll be able to find the problem if it is RV-related somehow.

I followed the wire coming out of the Ford-style solenoid, as you all suggested, and it goes straight down, under the truck, and is secured to the frame. I followed it back to the middle of the rig, near the rear axle. I don't know where it ends up, yet. This rig is set up for towing (original owner towed a boat with it, I think). I'm not sure if this was work done by a previous owner, or by Winnebago (although I would expect higher quality work from Winnebago?). Perhaps it was related to the rear towing wiring? Because the broken circuit breaker has been removed, this stuff is all disconnected, yet the parasitic draw continues...

I originally assumed these components were related to the starter, but apparently they are not. The truck starts just fine.

I appreciate your questions about my abilities with a multimeter- I may have made a mistake, I don't know. I originally tested this using my cheap, Harbor Freight digital multimeter, as well as an old analog multimeter. Yesterday I bought a new PT multimeter from O'Reilly, so I tried that today. I took pictures, showing around an 8.5 amp draw. When I first connected the leads, it was registering around 9 amps, and slowly dropped to the 8.4 amps shown in the photo. Hopefully I'm testing this right.

I haven't tried akwheeler's suggestion with using a test light, but that will be the next thing I try, assuming I have time to do that before I take it to the shop on Friday morning.

Thanks again for your time, and suggestions. I'll update when I know more.






Testing parasitic draw.

The reading fluctuates a bit. Seems to go down over time...

akwheeler

Looks like the proper hook up/setting to me, the next test is to leave that hooked up just like that for about 10 minutes and see if the draw goes away.
Many EFI vehicles will have a significant draw when you initially hook up the meter when the computer "wakes up" and it will "go to sleep" after a few minutes.
I don't remember the last time I checked but your amperage still seems higher than what I would suspect for that.
If you see a drop after a few minutes you will know that the computer shut back down and then you will see what is truly left for a draw and you can then proceed to use a test light or a second meter to probe fuses and see what is powered.
Then pull each powered fuse one at a time watching your meter for a current drop. Avoid the EFI and IGN fuses for now and don't disconnect your meter at the battery or you will go back to seeing the computer waking up and doing it's self checks.
I don't know for sure if this applies to your vehicle and my 3vz is 800 miles away right now. When I get home I'll see if I get an initial draw when I connect my battery and how much, unless someone else can chime in with some data.

rsmdon

On an rv a solenoid like that is sometimes used as a battery isolator. It looks like a ford starter solenoid but is rated for 100 percent duty as opposed to momentary use like a starter solenoid. The other part is an automatic resetting circuit breaker and could be used with a battery isolator.

RAD4Runner

Yes, most likely used as starter relay or battery isolator. That's where the starter relay is on first-gens MoreFunners
Not if it is an automatic. That's why I always stress, "Indicate model-year-engine-transmission-trim".

quint21,
Quick check: (make sure battery negative is disconnected) Disconnect alt-batt wire from screw/stud terminal on your alternator. Measure resistance from alt stud terminal to ground. Should be LOTS OF MEGA-OHMS.

quint21

Thank you, it's 1990 Toyota Pickup, 3.0L V6 3VZ-E engine, with an automatic transmission. I will check the resistance as you recommended as soon as I can.

RAD4Runner

Oh.. PLEASE ALSO DISCONNECT BATTERY POSITIVE TO BE SAFE.

You're welcome.
Automatic on older gens means most likely did not come with a starter relay. The Ford type relay (Ford calls it solenoid), is probably the relay retrofit, like Kid Vermicious in T4R posted.

quint21

I just wanted to give a quick update. I didn't have time to check on the alternator before I took it to the shop, but RAD4Runner, and those who suspected the alternator- your instincts were dead on. I took the rig into the shop yesterday, and the mechanic quickly tracked the problem down to the alternator, which, in his words "was burning up," when it was connected to power. You could smell it in fact, which, I don't know why I couldn't smell it at home, but you could smell the burning smell clearly at the mechanic's shop. With the alternator replaced, the amp draw is now back down in the normal range. As others noted in this thread, the mechanic wasn't super keen on the quality of the wiring leading from the truck battery to the RV coach battery's isolation solenoid, and he replaced part of that wiring. I purchased a new solenoid and a fuse holder from him, and will replace the battery isolation solenoid (and the broken circuit breaker) at a later time.

Thank you again for the time and care you took in answering my questions- it really helped!

RAD4Runner

Awesome!
I suspected bad rectifier diode(S).
So have you verified what this relay is for? Is it connected to spade terminal on starter solenoid?
https://cimg2.ibsrv.net/gimg/www.yot...888b06b5e3.jpg

quint21

RAD4Runner: the relay is connected to the RV's deep-cycle battery, usually called the "house battery" or "coach battery," which supplies power to the RV's living side (interior lights, water pump, etc). The relay acts as a disconnect, so when the ignition is off, the RV's lighting/etc won't drain the truck battery. When the ignition is on, the relay allows the truck alternator to charge the house battery.

On my RV, this system has been broken as long as I've owned it. (Either the circuit breaker, or the relay itself was always bad.) I never looked into it- I had always just assumed that my RV wasn't equipped to charge the house battery while I was driving. I did have the house battery die on me once when I was camping in a place that didn't have a power hookup. So, as a workaround I installed a solar panel on the roof, and replaced all the interior lights with LEDs, which took care of my power issues (the lower draw of the LEDs allows the solar panel to keep the house battery topped off). I'm going to replace this relay though- it'll be nice to be able to charge the house batteries with the engine, in case solar power isn't enough.