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Damn, I did not know the PAG oil is THIS freakin moisture addict !!!! I know it loves moisture, but this is nympho grade
Product Bulletin
Bulletin Number: 01-AC-2022-EU
Issue date: 04-2022
Compressor oils - What you need to know about DENSO compressor oils!
Part 3 Storage & Handling
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Per 10,000 PPM is 1%
Thank you Surya for shining light on this basic details made perfectly confusing.
I can guess the protection diode is assembled in parallel with PWM coil with reversed polarity to discharge every coil spikes.
When in doubt use a valve with diode protection. This is to prevent blowing up the MOSFET transistor in charge of pulsing duty cycle.
This valve involves power it is not a little cutie. Couple amps with voltage spikes in the 80Volts range!
Knowing MB we should consider the whole circuit of this solenoid valve - Where is it grounding ???
Having poor connections in a power switched circuit can really shorten life of VALVE + ECU.
We should check GND hopefully clean and not shared.
+++ From pdf/zip : diode protection
Both circuits are electrically identical.
The ECU is built to trigger a fault in case wrong part's in use and hopefully not blow up.
The point being double diode is better than zero diode. All PWM should have a diode regardless of ECU having one or not.
Creating unnecessary parts chaos is amazing!
Last edited by CaliBenzDriver; 04-15-2024 at 03:02 PM.
Hi Surya. I am confused when you correlate the compressor model number to the diode/non-diode application.
It is my understanding there is no such correlation; therefore, the confusion at non-MB specialists garages. The requirement to have a diode comes from the ECU, and depends on year and class. For a given compressor 6/7 (BU/EU) nn, the valve is selected based on the ECU for the given application.
You can find different valves for the same compressor when using the numbering 76E/BUnn sequence. I think the key is on the long number (A xxx yyy ww zz). For example, Toyota will use longer ECV valves, MB shorter ones for the same 7/6E/B type of numbering. It is a mind-boggling mess.
Application with DIODE
Application with WITHOUT DIODE, same 7SEU17C compressor type, but different DCP number
Hi Surya. I am confused when you correlate the compressor model number to the diode/non-diode application.
It is my understanding there is no such correlation; therefore, the confusion at non-MB specialists garages. The requirement to have a diode comes from the ECU, and depends on year and class.
Juan.... the pdf electric circuit shows differences -
Perhaps we can identify a "diode valve" application based on how curcuit sources the +12 from ECU or SAM.
Watch out for polarity in case of splicing new connector !!
Juan.... the pdf electric circuit shows differences -
Perhaps we can identify a "diode valve" application based on how curcuit sources the +12 from ECU or SAM.
Watch out for polarity in case of splicing new connector !!
That will be debugging, and reverse engineering the repair. I am OK with that once the parts have been bought. But from the top, w/o any electrical measurement, it is a daunting task to travel through all the compressor combinations on these cars.
One clarification, there is ALWAYS a diode. The question is where the diode is for the unprepared, .
For example, Ivan (PHAD) had a GL with a similar problem and he concluded the new compressor needed a diode by measuring the signal, voltages. However, it was obvious to me when he was disassembling the part out of the car, and when he showed the new one. No triangle, no yellow dot on the new part.
I am also confused on which MB has diode at its control module or at the compressor oil control valve ?
If Denso does produce such bulletin, that means they know people are confused.
Perhaps this is also the reason Denso does not sell stand alone control valve, we bust buy compressor assy.
If Xentry is correct, maximum current for AC control valve is 1 amp only. That is also based on Denso tech document.
So an electronic guy can work out the spike if there is a diode or no diode when testing this solenoid stand alone with without connection to any modules.
Make sure get the polarity right.
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Too bad the troubleshooting PDF is meant to be used by Denso Instructor and he will explain and add materials, so for us it is not full blast good document
The part that worries me is the Denso documentation I have seen so far does NOT explain how to recharge the system explicitly.
Denso is extremely careful in documenting the oil quantity and cleaning the system but it leaves the recharging to the vehicle manufacturer's specifications.
I have seen people recharging these systems with ECV similarly to fixed displacement compressors, i.e. put as much refrigerant until the pressures at the gauges are up to expectations. But those fail to understand, or not mentioning that such process is bound to fail unless you have the scan tool with you and check the ECV is 100% duty cycle enabled, i.e. working like a fixed displacement compressor.
if the technician does not use the scan tool, or gets distracted, and the ECV lowers the duty cycle, the technician may add more refrigerant until he/she sees the gauge at the expected location -> overcharged.
So now, a technician, or DIY needs: pressure gauges, proper scan tool and watch for at least 4 parameters: clutch engaged, low and high pressure and ECV at 99+%.
Process bound for problems. That is why the "recharge by weight approach", scale and done.
Yes, recharge by pressure is NOT allowed, more so variable displacement compressor.
By WEIGHT is the only way to go.
Hence the R134A by grams comes from Mercedes as they worked it out with Denso engineers .
04-15-2024, 11:40 AM
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