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ACCII Amplifier voltage draw

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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.


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. 

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.

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!

Then I'd suspect a bad/weak amplifier or a vacuum leak.  Both can/will cause the issues you're experiencing. 


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