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trying to pick some brain... by CRSMP5 on 05 Apr, 2013 19:42
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couple issues... or oddities of the past few day..
who has tested a w terminal on a 120amp serp alt off a 96-99.5 tdi?
when i say test.. take say vdo diesel tach gauge, power, ground, w and hook directly to batt/alt? i use a test light to play dummy idiot light and use spare plug i have to tap into the alt..
does it work??
why...
my 90 amp alt on the kubvan works... off yes 1800rpm is idle.. but it gives a signal...
now to hook up to bbob's tdi-m swap in his b3.. nope nada.. f you... kick in balls for 12+ hr...
ohhh crap.. lets go try totaled 97 passat tdi everything works on... nope nada.. nothing... best part.. when unplugged at alt.. tach/oil system STILL WORKS!!!!
talking to myke_w same issue.. gotta call nathen tomarrow as he did something to get to work for myke.. but was like 5k at idle..
who else has had a issue???
-------------------problem #2-----------------------------
kubvan... took to cali.. on way to cali headed west out of denver thru the mountain pass i spiked 1450 on egt.. now oil 250miles/qt.. still making 15psi of boost when towing car!!! the rubber connector between turbo and my ic pipe... split in half... big hole in it... still making 15psi of boost at intake manifold...
how.. no clue.. egt not even high....
going to test fixing that to see if my oil consumption goes up/down or stays same... but how does it sill make boost w/split.. and can split cause a odd venturi effect to suck oil thru the breather due to said hole on the cold side exit of the turbine??
there you go.. pick some brains..
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#1 by the caveman on 06 Apr, 2013 06:45
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Been a while since I had to check one but here goes. As far as I know, disconnected the w terminal gives out nothing from the alternator side. The reason you may be getting something is because of your high idle.
Normally you should get a 12v, 500 mA signal from the instrument cluster. The alternator provides the "ground" side of the circuit. In short , it is a failsafe, feedback circuit that needs both ends to work, therefore providing both a field signal for the alternator and the warning signal for when it fails. I don't want anybody to jump on me if I got it a little wrong, but that is how it basically works -
#2 by CRSMP5 on 06 Apr, 2013 08:44
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gauge on my 90amp serp alt is high as ive always felt its off due to serp design... its a gauge calibration thing.. ive run same gauge on normal w alts in the past no issue...
the issue is... of 3 120 amp tdi serp alts... none have a working w terminal.. will not flicker a w terminal tach.. stock vw cluster or my assy one!!
we took bbob's mk2 eco harness out.. put his b3 harness and cluster in.. no prob... put his mk2 stuff in b3.. fail.. after 13 hr of dickround.. i pulled my 3 wire assy tach.. plugged in under hood where exciter and all works, charges so on.. but no w signal... then tryed in person w tdi-e set up.. still fail.. then called myke_w who i knew had issues with his.. again same issue...
im kinda wanting to know... any one have a tdi serp set up thats 120a that the w actually works on... idi.. serp swaps apply.. is it a w terminal??? if not what is it? -
#3 by wolf_walker on 06 Apr, 2013 11:08
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Quick google for a late 90's Passat TDI says it does not get the tach signal from the W terminal like older models.
That's all I got.
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#4 by 92EcoDiesel Jetta on 06 Apr, 2013 12:51
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CRSMP5 AFAIK, when I had a Passat B4 TDI, the tach get it's signal from the ECU which gets it's RPM signal from the crank position sensor, not from the 120A alternator W terminal. The B4 cluster tach is stepper motor driven, not an analog movement like idi diesel and gasser tach's. I have never looked to see if the 120A B4 Passat alternator has a W terminal output or not. My guess is it does not since the W is not needed for anything I can think of in the B4 Passat.
It's hard to follow what configuration you have in terms of wire harness and cluster. If you pm me I can give you my phone # and talk you through what I know regarding VW diesel tach's.
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#5 by bbob203 on 06 Apr, 2013 14:01
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CRSMP5 AFAIK, when I had a Passat B4 TDI, the tach get it's signal from the ECU which gets it's RPM signal from the crank position sensor, not from the 120A alternator W terminal. The B4 cluster tach is stepper motor driven, not an analog movement like idi diesel and gasser tach's. I have never looked to see if the 120A B4 Passat alternator has a W terminal output or not. My guess is it does not since the W is not needed for anything I can think of in the B4 Passat.
It's hard to follow what configuration you have in terms of wire harness and cluster. If you pm me I can give you my phone # and talk you through what I know regarding VW diesel tach's.
This is for my car I texted you last night.. -
#6 by bbob203 on 06 Apr, 2013 15:33
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From a guy on tdi clubQuote from: Alchemist;4149097
If the alternator you are using is from a TDI engine such as the 1Z, it will not have a W terminal. With TDIs, the alternator has D+ and DF terminals. DF reports alternator load to the ECU so it can control high current loads such as coolant glow plugs. Since TDI tach signals are generated in the ECU the W terminal is not needed.
You may have to use the AAZ alternator to get the tach to work or get a Dakota Digital converter to make the signal compatible.
Paul
I have Dakota Sgi 8 so I'm not sure if it will work or not. -
#7 by bbob203 on 06 Apr, 2013 15:37
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#8 by CRSMP5 on 06 Apr, 2013 15:37
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correct 92.. my og post says a tdi-e does not use the "w" as we figured out yesterday..
set up.. tdi-m.. all it needs is a w source to feed its aaz diesel cluster.. which works on ce2 jetta with w terminal alt..
but the plug for the exciter has 2 wires.. th eblue.. and a red w/black stripe just like a 92-82 w terminal set up.. and on the 90a serp lt it is a w...
the question is/was does a 120 have a w signal... who has successfully used the 2nd wire for a w signal?? or have we all over looked this??
when i got my 90amp one from zone.. only one i could find.. 120 not avaliable anywhere for a price i was willing to pay.. was 3x as much... in a car with no power windows and such that cam estock with a 55a i saw no reason 90 would not be enough.. my b3 wagon has 65a on it.. but its wired up using the same 2nd wire for w.. and works... but in the past 2 days i figured out what comes with a 90a.... ll the tdi ive looked at are 120... so 90 aaz? so w works?? they lacked comps and had tachs..
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#9 by the caveman on 06 Apr, 2013 15:50
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oops, I'm stupid. I thought you were talking about the connection for the alternator light. Only checked the w terminal once, seem to remember using a scope to see what the signal was. Ignore all i've written previously, nothing to see here, carry on...
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#10 by wolf_walker on 06 Apr, 2013 15:55
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http://www.vwdiesel.net/forum/index.php?topic=27149.0 that probly isn't much help but it's a technical explanation of the output
so you can know what you are looking for. -
#11 by bbob203 on 06 Apr, 2013 17:16
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Another thought I'm having is if a clutched alt pulley will mess up my tach reading?
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#12 by bbob203 on 06 Apr, 2013 18:14
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#13 by bbob203 on 06 Apr, 2013 18:19
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#14 by bbob203 on 21 Jan, 2014 07:37
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Back from the dead. I scored a 120 amp alternator last night from a 93 eurovan it has a W terminal on it. I will post the part number when I get it written down.