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Parasitic drain identified on HAZ/TRN fuse... abnormal?

sim303

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Jan 31, 2017
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uk
Hi all

Spring is here and it's high time I investigated why my battery fails to start the car after just a few days.... (and yes, it is just one battery - the other is no longer part of the main circuit and instead serves as a leisure battery for auxiliary gear).

...so I spent much of Saturday measuring current drawn from the battery with various fuses pulled etc. I have three pages of notes, having measured with each fuse pulled in turn (engine fuse box and passenger footwell box). But the pertinent findings are these (all are measured with the alarm armed):

Base reading (A) - Overall drain, everything connected: 75-78mA

ENGINE FUSE BOX:
as per (A), minus RADIO fuse: 72-73mA
as per (A), minus HAZ/TRN fuse: 32-34mA
as per (A), minus ALL engine-box fuses: 27mA

PASSENGER FOOTWELL FUSE BOX:
ECU-B drawing 15mA

All fuses present EXCEPT HAZ/TRN and ECU-B: 15mA (Which makes sense: (A) - HAZ/TRN - ECU-B == 75-45-15 = 15mA )

~

Thoughts so far.... A total drain of 75mA does not sound ridiculously high, and certainly not enough to kill a healthy battery in a few days. Therefore I conclude that my battery is in a bad way and needs replacing. That's why I did this exercise - as I don't want to splash out on a new battery only to kill it with a bad current drain.

BUT.... 75mA _is_ higher than the Toyota recommendation (35-50mA as I recall), AND, the 45mA draw measured on the HAZ/TRN fuse seems unexpected, assuming that fuse really does only do the Hazards and Indicators. Subtracting that 45mA would seem to put me back within Mr T's expectations. Any thoughts on that? Is there some other function for that circuit? Is it tied into the alarm perhaps? Or maybe some previous owner has tied in some piece of junk device into the HAZ/TRN line? Should I trace that line further?

Thoughts welcome, (and if anyone is bored/interested enough to measure their own HAZ/TRN fuse current, I'd be really grateful! :)

sim
 
Do you have a trailer socket and/or an indicator relay unit fitted? If so, disconnect these and check again. It may be that there Water present or tracking on a circuit board that has occurred.
 
Hi

There used to be one yes, but I removed it and the towbar a couple of years ago. Its wiring didn't look too wonderful as I recall, and I think I removed all the obvious non-stock cable. Maybe I can get underneath again and disconnect the loom connector blocks on the rear crossmember and inside the jack compartment and see if that has any effect on the measurement.

Would you say that the HAZ/TRN circuit should indeed be a zero drain circuit when not in use? i.e. it should not have any hidden 'extras' running off it, from the factory I mean? I will try to find a circuit diagram to check....

Thanks

sim303
 
Before you go further, check 3 things:
That you wait until 5 mins after taking the key out, closing and locking the doors, before you measure.
That you don't have a OBD-dongle sitting in the OBD port.
That you don't have a CD-changer with a stuck CD in it.
 
My experience is not if 100 series like Uhu’s but I would expect the Haz/TRN circuit to be on its own and a zero power drain at standby. However a 100 series circuit diagram would confirm this or not. Most likely suspect is a turn relay as this is often an after market addition to the turn signal circuit. Often located in behind a light cluster and usually uses a permanent feed. I’ve seen these sitting in plastic bags before, half full of water being nicely warmed by the 12v supply.
 
Before you go further, check 3 things:
That you wait until 5 mins after taking the key out, closing and locking the doors, before you measure.
That you don't have a OBD-dongle sitting in the OBD port.
That you don't have a CD-changer with a stuck CD in it.

I did wait a little while, but will give it a good 5-10 mins and check again to confirm. Nothing in the OBD and the CD changer no longer exists :)

Thanks

simon303
 
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My experience is not if 100 series like Uhu’s but I would expect the Haz/TRN circuit to be on its own and a zero power drain at standby. However a 100 series circuit diagram would confirm this or not. Most likely suspect is a turn relay as this is often an after market addition to the turn signal circuit. Often located in behind a light cluster and usually uses a permanent feed. I’ve seen these sitting in plastic bags before, half full of water being nicely warmed by the 12v supply.

I was able to find the circuit diagram for the HAZ/TRN circuit last night and you're right - it doesn't do anything else. Just a turn relay and a towing relay, switches, connectors and lamps. In light of that, and indeed your comments regarding turn relays, I am quite hopeful that I will at least be able to eliminate parts of the circuit (removing bulbs etc) and isolate the problem. 45 mA doesn't sounds like a lot but for a car that is not driven daily every drain on the battery is significant, and fixing this would halve my total drain :)

I'll post again once I've had a chance to investigate...

Thanks again

sim303
 
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Just to clarify, my reference to a turn relay was intended to read towing relay or sometimes called a turn signal amplifier, indicator relay, etc. The modules that buzz when a trailer is connected, anyway.
 
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Just to clarify, my reference to a turn relay was intended to read towing relay or sometimes called a turn signal amplifier, indicator relay, etc. The modules that buzz when a trailer is connected, anyway.

Ah I see, yes. I tried to look for it yesterday (supposed to be in the bundle of cabling inside the jack compartment at the back) but couldn't see any likely candidate. It's not very pleasant in there - Dinitrol wax bundles of cable with foam wrapped connectors... However... (see next message...)
 
The intrigue continues. According to the HAZ/TRN system diagram, there should be no permanent consumers on that circuit except for the obvious turn signal components.

But, I found a couple of things that contradict this in my case.

1) Pulling the fuse causes the alarm siren to beep a few times (to warn of battery disconnection, I presume). So the alarm is definitely tied into this circuit, despite the diagram. (And it would have to be, otherwise how would the indicators flash on arming?).

2) I previously reported a current drain through this fuse of around 45mA when I tested at the weekend. Testing again last night - it was around 120mA, which is more serious.

3) Based on (1), I disconnected the alarm siren. Drain through the fuse when armed dropped from 120mA (2) to 40mA. (and when unlocked, from 95mA to 18mA).

So this suggests to me that the siren module is suspect. Maybe it has a battery which is dying and drawing current (which might explain the variation in readings from 45mA to 120mA). I had to stop due to fading light - I'm not convinced that the siren is the sole problem, but the quest will resume!

sim303
 
Is it an aftermarket alarm Sim? Disconnecting it should have set it off so your thought on battery is a good one. They can go bad and become problematic.
 
I'm not aware of it being aftermarket, but I'm not sure how I can check that. I assumed that by that point (2002) most cars had factory alarms as standard. If I could find the part number for the siren module, and find one on new or on ebay for a reasonable price, I'd be willing to take a punt on trying that, but so far, I have not been able to identify it. I'm not going to give up on this though!
 
Open up the siren if possible without mauling it, and have a looksee. If there’s any corrosion or water damage evident then that may be your smoking gun. Capacitor’s also age and need replacing after a while. It certainly seems that there is drain from the alarm siren. The question is, what’s normal? And is it significant? Does your battery still drain if you disconnect the siren? That could be the acid test. Also, have you had your battery (ies) tested on a digital tester thingy? I had a similar scenario where I chased around for a small leakage but found my batteries had in fact died.
 
You dont say what year your 100 is but if its an early one it could be a version of the TVSS alarm. The 3B version was fitted to the last 80’s and first 100’s and there are also later versions. My (TVSS3B) siren module went bad due to water ingress so I replaced it with one from an early Avensis as the wiring was (almost) the same. Just re-arranged the pins in the plug on the unit and replaced the rechargeable batteries. The draw on my batteries when parked and locked is <40ma. I had a parasitic draw problem (350+ma) flattening the batteries several years ago which turned out to be a badly corroded intake air heater relay but I dont think the 100 series has this setup.
 
Afaik all 100s in Europe came with factory alarm.
 
Open up the siren if possible without mauling it, and have a looksee. If there’s any corrosion or water damage evident then that may be your smoking gun. Capacitor’s also age and need replacing after a while. It certainly seems that there is drain from the alarm siren. The question is, what’s normal? And is it significant? Does your battery still drain if you disconnect the siren? That could be the acid test. Also, have you had your battery (ies) tested on a digital tester thingy? I had a similar scenario where I chased around for a small leakage but found my batteries had in fact died.

Removing and hopefully opening the siren was going to be my next step, at the weekend if the stars align correctly. It must have either a battery or capacitor into in order to sound the disconnection beeper at least, so if I can get to those I might be able to renew them. That's the plan, but I dare say that removing it (rusted bolts, poor access) and opening it will probably full of "entertainments"!

I haven't yet tried the battery with the siren disconnected, but to be honest I think the battery is already knackered (probably by being repeatedly drained flat) so it would be hard to check. The purpose of this exercise is really to reasure myself that the drain is within reasonable limits before risking a new battery.
 
You need to get your battery tested really rather than guess, unless it’s of an age and obviously bad. A Ctek charger is fantastic for battery regeneration and has helped with 4 dying batteries on a local fork lift.
 
You dont say what year your 100 is but if its an early one it could be a version of the TVSS alarm. The 3B version was fitted to the last 80’s and first 100’s and there are also later versions. My (TVSS3B) siren module went bad due to water ingress so I replaced it with one from an early Avensis as the wiring was (almost) the same. Just re-arranged the pins in the plug on the unit and replaced the rechargeable batteries. The draw on my batteries when parked and locked is <40ma. I had a parasitic draw problem (350+ma) flattening the batteries several years ago which turned out to be a badly corroded intake air heater relay but I dont think the 100 series has this setup.

It's a 2002 model year so I guess not the same alarm, but I haven't been able to find any info so far.

40mA sounds much closer to what I would expect (I think I recall a technical document from Mr T quoting an expected range of 35-50mA, but I can't swear to the accuracy of my memory :)) So although my drain isn't stupidly high, at 85-120mA (depending on when I tested it), it does not sound right, and even at that rate would kill a good battery in under a couple of weeks.
 
Weekend update....

Using the circuit diag for the suspect HAZ/TRN circuit, I saw that the the first component beyond the fuse (apart from a loom connector) is the T11 flasher unit. Disconnecting this would effectvely take the entire rest of the indicator circuit out of the picture. I did this, and it had no effect on the drain. Further, the alarm flash still worked, so that tells me that the alarm does not use the normal flasher unit, but sends its own signal to the indicators. So somewhere, not shown on my diagram, the alarm is on this circuit.

Anyway, as I was fiddling with the centre floor console (the one with the gear sticks), I was annoyed by the alarm-armed LED, which was hard wired and prevented the panel being removed completely. I ended up cutting the cable with a view to putting a connector on it, but whilst it was cut I measured the drain on the HAZ/TRN circuit again:

With LED installed:
Unlocked: 18mA Locked: 42mA

With LED cut out:
Unlocked 18mA Locked: 18mA

So that blasted LED, which was clearly some afterthought or third-party fit (no connector, two individual wires without wrapping...) was eating 24mA whilst the car was locked.

Ok, so 24mA is not a great deal, but it's more than I want to spend on an paltry LED! Removing this, and the siren module, has brought my sustained drain current down to 62mA, which I reckon is acceptable.

As for that siren module, I have been able to find 6 2/3AAA Nimh cells and will rebuild its battery pack. Hopefully reinstating that will then not have too detrimental an effect on my drain.

I think I will leave it at that for now and see how it goes for a little while. Thanks for all the help!

sim303
 
PS.... for general interest...: I spotted the alarm module itself. It's a TVSS IV-S.
 
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