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#51
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How can it be that you are not changing the checksum when you change other values. I thought maybe if the multiple changes were symmetric they might offset and the checksum would remain unchanged, but that does not appear to be the case with the new temperatures you chose. What obvious feature am I not understanding? Thanks.
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2001 X5 3.0i, 203k miles, AT, owned since 2014 |
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#52
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I was thinking the same thing. Once you know the Ω value at a few values you can tweak the apparent resistance with either series or parallel to offset the temp to have the light come on at any temp you want.
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2011 E70 • N55 (me) 2012 E70 • N63 (wife) |
#53
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So for 15ºC and below, the gauge is at the bottom. From 15ºC - 50ºC, it moves from ø0º to 31º; from 50 to 75ºC, it moves towards ø90º. From 75º-115ºC it stays at that angle. From 115 to 124ºC it gets to ø148º, and then 125ºC onward it jumps to ø164º. 15ºC - ø0; 60ºC - ø31; 85ºC - ø90; 95ºC - ø90; 110ºC - ø148; 115ºC - ø164 The 22 page thread I posted from E46F is a good read that explains everything in detail.
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Digital Competition Systems The older I get... The faster I was... No Fear |
#54
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Yes, so that's my basic dumb question ... if you change one of the hex values, isn't that something that the checksum checks? And if so, wouldn't the checksum value for that line change? Handled automatically somehow?
No doubts about the needle angles and old vs. new temperatures you want programmed in there. Just the checksum thing does not make sense to me. I had thought that maybe if the changed parameters were all symmetric changes, so some went up by the same amount that others went down, the required checksum changes might self-cancel. But it does not look like that is the case with the numbers here.
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2001 X5 3.0i, 203k miles, AT, owned since 2014 |
#55
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In this case there is enough eeprom space to keep a duplicate line of the code so there is no checksum needed.
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1988 325is (purchased new) sold 2004 X5 3.0 2005 X3 2.5 2008 X5 3.0 (new to me) |
#56
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I guess storage is cheaper that CPU cycles.
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Wayne 2005 BMW X5 3.0d (b 02/05) 2001 BMW F650GS Dakar (b 06/01) |
#57
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No, first of all the 1/2 of the temp sender that works the light appears to be an old skewel normally closed switch, so can't really do much to change that other than maybe use a different sender. The wiring diagram for the temp sender shows both sides the same and NTC resistors internally but I think that is misleading and from what I can tell. I am going to double check that though. So what I am trying to do is read the temp from the DME side and turn the light on with that.
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1988 325is (purchased new) sold 2004 X5 3.0 2005 X3 2.5 2008 X5 3.0 (new to me) |
#58
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Thanks, I figured it was something like that.
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2001 X5 3.0i, 203k miles, AT, owned since 2014 |
#59
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OK, I actually got into the harness(and put a new battery in my multimeter) and did some more serious testing and I was wrong about the wiring diagram being wrong! Sorry guys, but might be good news. The light side of the sending unit appears to be indeed a NTC resistor although with a completely different resistance value than the DME side. So might be entirely possible to tweak it as Andrewwynn suggested. Will keep you guys posted.
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1988 325is (purchased new) sold 2004 X5 3.0 2005 X3 2.5 2008 X5 3.0 (new to me) Last edited by 80stech; 12-23-2018 at 10:06 PM. |
#60
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I did a fair bit more investigating and there is definitely more going on here than I thought! Anybody dig into the temp light before, or am I in uncharted territory? Either way I am up for the challenge but if anybody can add some knowledge I would not complain! As it sits now I think there is some information sharing going on between DME, the dash, and both parts of the sending unit(or maybe I blew something in the dash) so planning on looking in that direction next.
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1988 325is (purchased new) sold 2004 X5 3.0 2005 X3 2.5 2008 X5 3.0 (new to me) |
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