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#1
01-05-2003, 11:03 PM
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420SEL Idle Valve Voltage
Does anyone know what the voltage should be at the idle control valve connector while the car is at normal operating temperarure and at idle?
I performed the current test described in the manual and I mesured about 960 mA which is within specs. However, the voltage is less than 5 Volts. None of the manuals I read indicate the voltage. Correct me if I am wrong, but the voltage should always be 12 Volts while the current varies regulating the valve opening. Any help would be appreciated! Thanks! Leon 
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#2
01-06-2003, 03:47 PM
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Not sure what the correct voltage should be but I had reason to check mine on a 1991 420 SEL just this past weekend and if I remember it was about 5 volts. Through the probes, i could feel the regulator "dithering".
J.Chip
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#3
01-06-2003, 03:50 PM
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leon, you are correct it should be 12V. Checked the forum and found this discussion.
86 560SEL cold start/rough idle Unfortunately, not sure why this would occur. m
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Martin Ingram Colorado Springs 2005 320 CDI 2006.5 VW Jetta TDI 1991 560SEL (179000 Sold) 1972 280SEL 4.5 ('The Lead Sled' 320000 miles when sold.) 1972 220D (225000 when sold)
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#4
01-06-2003, 04:27 PM
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Thanks Steve.
That makes a lot of sense. martin
__________________
Martin Ingram Colorado Springs 2005 320 CDI 2006.5 VW Jetta TDI 1991 560SEL (179000 Sold) 1972 280SEL 4.5 ('The Lead Sled' 320000 miles when sold.) 1972 220D (225000 when sold)
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#5
01-06-2003, 04:54 PM
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Thanks Steve. Your answer makes sense. I am assuming that this is the reason why none of the shop manuals give a DC voltage. Based on the reading of 960 mA, I will assume that the controler board is functioning correctly and that perhaps my idle valve is defective. Right?
Leon
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#6
01-06-2003, 05:35 PM
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If you look at the signal with a scope you will see a square wave at battery voltage with a constant frequency and a varying duty cycle.
What this means is that the valve is being pulsed against the spring that opens it. Depending how your volt meter sees this one usually sees the average voltage with a 50% duty cycle and 13v idle voltage most meters would see 6.5volts. The controller has the capability to go to 70% duty cycle on or off (I think). This would place the control range between 9.1 and 3.9v with an averaging voltmeter. Instantaneously the voltage is either battery voltage or zero.
__________________
Steve Brotherton Continental Imports Gainesville FL Bosch Master, ASE Master, L1 33 years MB technician
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