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'04 330ci 6MT
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Discussion Starter · #1 ·
We all know the E46 cooling system can be a bit fragile, and overheating from a failure can cause irreversible engine damage. We also know that the gauge in the instrument cluster is not a regular gauge, with the needle pointing unwaveringly to 12 o'clock for the entire 75-115C range. Beyond that, it moves very quickly into the red. There's no light or gong to warn you when that's happening, and unless you happen to glance at the gauge at just the right time it'll likely be too late by the time you notice.

I've recently come across a number of dashtop electronic gauges on ebay that plug into the OBDii port, and can display various parameters. Like this one:

909517


Coolant temp is one of the parameters monitored. You can set an alarm for whatever value you choose, and it'll sound an alert and flash the temp in big red numbers if triggered. Only downsides I can foresee is there'll be a slight 10mA residual current draw, so I'd want to unplug it if the car's going to sit unused for some days, and it'll probably look a bit cheap and tacky on top the dash of a BMW. But, assuming it interfaces OK with the car, it'd be a cheap way of making sure the engine never overheats. I thought I might get one to try out at least if no-one here already has. I searched the archives but couldn't find a thread on them, please someone shout if they've been discussed before.
 

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2001 325ci
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they are nice to have. some of us have ultragauge. I have mine set to monitor coolant temp, battery voltage, and long range fuel trims on my main page. not sure about residual current draw, goes off when I turn car off. I never unplug.
 

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'04 330ci 6MT
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Discussion Starter · #3 ·
Thanks LL. The Ultragauge looks a much nicer device than the toy-like ebay specials I've been looking at it. It is 3-4 times the price though, at least over here. I've ordered a cheapie to play with for now, if I like the concept but not the execution I'll consider replacing it with an Ultra now when it inevitably fails :)
 

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Recoding the gauge isn't hard- that's what I've done, and it works.

t
 

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Discussion Starter · #5 ·
I've seen the threads on using PA Soft to do that. It removes the problem with the needle pointing straight up over such a wide range, but you still have to actively scan the gauge to check where it's at. I like the idea of an alarm going off if the temp reaches, say, 115 C to draw my attention to it. I might actually do both though.
 

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Discussion Starter · #6 · (Edited)
Just to follow up, I bought one for £15 (vs £96 for an Ultragauge). I went with a clean install under the LCM rather than having it perched on top of the dash like a cheap sat nav. I ran the cable through the driver's cubby. It's not in my normal line of sight when driving but that's OK, I bought it to have an audible alarm and if that goes off I'll know to immediately check it and the OE temp gauge. Here it is, with the car warming up at idle after a cold start:

910081


I'd have liked a smaller display ideally but I can't argue with the price! The main thing is it seems to work just fine. I'll be changing the thermostat next week (it's operating fine but INPA tells me its map controlled heater element has failed) and it'll be reassuring to have an alarm if the temp rises above normal afterwards should I fail to get all the air out when bleeding.
 

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Discussion Starter · #7 ·
Just a quick update on this. Had an ammeter on the car the other weekend and discovered the sleeping current draw had increased by 30mA leaving this connected. That wouldn't trouble a daily driver but my car sees less frequent use and an extra 30mA almost doubles the standard sleeping draw. So I now disconnect it from the OBD port when I park it up, in case it's a couple of weeks before I use the car again. It retains its settings whilst disconnected, handily.
 

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2005, E46 Convertible, 330CI M Sport Auto, Mystic Blue, 76k Miles
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Can you post a link up for that, please?
 

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Discussion Starter · #9 ·

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2004 330Ci 115k miles
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Just a quick update on this. Had an ammeter on the car the other weekend and discovered the sleeping current draw had increased by 30mA leaving this connected. That wouldn't trouble a daily driver but my car sees less frequent use and an extra 30mA almost doubles the standard sleeping draw. So I now disconnect it from the OBD port when I park it up, in case it's a couple of weeks before I use the car again. It retains its settings whilst disconnected, handily.
Would be nice if that gauge have a power switch on it to avoid parasitic current drain when rhe engine is off.
 

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Discussion Starter · #12 ·
Would be nice if that gauge have a power switch on it to avoid parasitic current drain when rhe engine is off.
Maybe, if I run out of mini-projects this summer, I might look to see if I can interrupt the permanent 12v supply to the OBD2 port and route that instead via a relay triggered by ignition key switched 12v. But I'll probably never get around to it :)
 

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2005, E46 Convertible, 330CI M Sport Auto, Mystic Blue, 76k Miles
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I was looking at that thread where the guys reprogrammed the temp gauge to read more accurately. I'll have a proper read and get PA Soft and attempt it.
I do have OBD Fusion running and this is really good for keeping an eye on it.
 

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Discussion Starter · #14 ·
I was looking at that thread where the guys reprogrammed the temp gauge to read more accurately. I'll have a proper read and get PA Soft and attempt it.
I do have OBD Fusion running and this is really good for keeping an eye on it.
Whatever works for you (y) . That's certainly neater than sticking something from China on your dash but having a needle that points past 12 o'clock earlier is only useful if you happen to look at it when it does..
 

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2001 325ci
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elfer, is your device still on when engine off?
my UG is off when engine off. i never unplug. i doubt battery draining thru OBD port when left plugged in.
 

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Discussion Starter · #16 ·
No, the screen goes off but there's still a residual current draw of 30mA. When it's off it monitors OBD voltage in order to know when to turn on (ie when the voltage has increased because the alternator is running), and that monitoring must be what draws the 30mA..

Have you actually measured sleeping draw with and without your plugged in? If you drive your car regularly I doubt you'd notice a small extra draw. Though, as I said before, mine was a £15 ($20) solution rather than the nearly £100 the UG is here, so I wasn't expecting it to compare! :)
 

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Have you actually measured sleeping draw with and without your plugged in? If you drive your car regularly I doubt you'd notice a small extra draw.
not really have measured. and drive over 60 miles one way to work (3 or 4 times a week on 12hr shifts).
i also have a plug-in (on cig lighter) volt meter (plus usb) where i can check voltage anytime, engine on/off. that would draw a bit since its illuminated. also always plugged in. but doesn't really drain battery.
 

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When it's off it monitors OBD voltage in order to know when to turn on (ie when the voltage has increased because the alternator is running), and that monitoring must be what draws the 30mA..
makes sense.
also, from UG site, "When UltraGauge is first attached to the vehicle’s OBD-II connector it is immediately powered, as the vehicle’s OBD-II connector is always powered. Once connected UltraGauge will begin scanning the interface to determine the vehicle’s protocol. The vehicles ignition must be in the RUN position in order for UltraGauge to communicate with the vehicle’s Electronic Control Module (ECM). The ignition must remain in the RUN position during both scanning and gauge discover."
 

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Discussion Starter · #20 ·
not really have measured. and drive over 60 miles one way to work (3 or 4 times a week on 12hr shifts).
i also have a plug-in (on cig lighter) volt meter (plus usb) where i can check voltage anytime, engine on/off. that would draw a bit since its illuminated. also always plugged in. but doesn't really drain battery.
Like I say, using the car regularly - as you do - you won't notice it. But mine doesn't see frequent use at the moment. We're in our third lockdown here and I might only use my car once or twice this month. Going from 40mA to 70mA sleeping draw would almost halve the time the car can sit without the battery needing to go on a charger.
 
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