Author Topic: ACCII Amplifier voltage draw  (Read 168 times)

daantjie

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ACCII Amplifier voltage draw
« on: 28 October 2021, 04:23 PM »
Hi guys

Been in ACCII purgatory for a while now, always fun, but it appeals to my slightly masochistic nature when it comes to older Benzes I guess ::)

Question for the ACC gurus...I have read a ton online on various readings you should be getting with the water valve moving by way of the signal it gets from the amplifier.  However most folks say that you need to see about 1V with system OFF, which is fine, and then up to 6ish V with the valve moving.  What I cannot seem to find is what the readings should be for example at max hot thus valve fully open?  Or max cold for that matter.  I am getting readings of 2 - 3 ish V when the valve has maxed out (not parked, just full hot or full cold in for example AUTO HI).  Is this right?

It parks fine when I turn the key off, and then the voltage drops to 0 which is correct, but I am bit stumped by these "other" positional volt readings at pin 1 and 7 of the amp...

Any sage advice appreciated as always.

Cheers
« Last Edit: 28 October 2021, 06:49 PM by daantjie »
Daniel
1977 450 SEL 6.9 - Astralsilber

UTn_boy

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Re: ACCII Amplifier voltage draw
« Reply #1 on: 01 November 2021, 09:38 AM »
If the resistance chain has reached equilibrium then there shouldn't be any voltage present.  Otherwise the servo would be constantly moving.  There may be trace micro voltages present all of the time, but not enough to move the servo. 
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daantjie

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Re: ACCII Amplifier voltage draw
« Reply #2 on: 01 November 2021, 10:42 AM »
Thanks Aaron that was what I was suspecting.  Think I need to check the resistor chain again and see if all the sensor resistance readings are within range.
Cheers
Daniel
1977 450 SEL 6.9 - Astralsilber

daantjie

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Re: ACCII Amplifier voltage draw
« Reply #3 on: 17 November 2021, 09:58 AM »
Ugh, true to form the infamous ACCII system is giving me fits >:(

I have checked the resistor chain, all within spec.  It seems like an intermittent fault in that the amp gets hot, and then the servo stops responding, result is the hot water valve seems to be jammed shut so even on DEF you only get cold air from the vents.  It works fine at first start, DEF gets piping hot air, then as you cycle to BI LEVEL and AUTO HI, with temp set at 65, it does shift to cooling, which makes sense as the cabin is now hot.  But then if you try and cycle back to hot by way of DEF or AUTO HI (wheel set to max temp), no hot air whatsoever, as well no parking when you turn off ignition.  So it's like the amp overheats and then just craps the bed with failure mode showing as only cold, no heat.

All other functions work fine, flap open and close, blower blows perfectly fine with step up and down in speed. Servo is refurbed, amp is new unit from Programa. Servo responds to direct power being applied, also resistance is within spec on the servo.  Ugh I really do no want to go the Unwired Tools route here, already pissed away too much money on this Chrysler POS!
« Last Edit: 17 November 2021, 12:44 PM by daantjie »
Daniel
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Re: ACCII Amplifier voltage draw
« Reply #4 on: 19 November 2021, 03:18 PM »
Then I'd suspect a bad/weak amplifier or a vacuum leak.  Both can/will cause the issues you're experiencing. 
1966 250se coupe`, black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3, papyrus white/dark red leather
1971 280sel Black/black leather
1973 300sel 4.5, silver blue metallic/blue leather
1976 280s astral silver/blue MB Tex

daantjie

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Re: ACCII Amplifier voltage draw
« Reply #5 on: 19 November 2021, 04:06 PM »
Thanks yes I swapped back in my old amp and it actually runs the servo much stronger than the Programa amp so I'm returning the Programa amp.  Problem now seems intermittent which of course is the most frustrating fault to trace >:(
Daniel
1977 450 SEL 6.9 - Astralsilber