MAF Sensor Troubleshooting

[markob]

I am pretty sure my MAF sensor is bad, Before I replace it I am trying to check my wiring to MAF and voltage to and fro the MAF. One thing stands out, My burnoff is always hot as in my wire is glowing all the time. My question is how does pin 3 in the MAF sensor get it's charge? Does the signal come from the LH Module or is it hot all the time and switches on and off from the sensor? Just for reference my wiring harness both upper and lower has been replaced with new.

 

[JC220]

The link below is for a 1992 500E engine schematic:

http://www.autolib.diakom.ru/CAR/Mercedes-Benz/1992/500E/SYSTEM%20WIRING%20DIAGRAMS/4340.pdf

RE MAF testing please refer to this thread post #67 and #69

The image attached describes the function of the 500E MAF sensor

 

[195910]

The MAF burn-off function is controlled by the LH unit. There are 5 pins (Ground, 12V, signal to LH, Burn-off from LH).
Is it constantly on? warm up or once warm ?

 

[195910]

Question: is Rk the Intake air temperature sensor ? or a sensor in the MAF ?

 

[Klink]

Question: is Rk the Intake air temperature sensor ? or a sensor in the MAF ?

Inside the MAF.

 

[markob]

Yes it is constantly glowing red and the car runs like crap, If I disconnect it will smooth out and run well again

 

[gsxr]

Do you have another LH module to use as a test? Any LH module for M119 will work for a quick test, you're looking to see if the MAF stops glowing red all the time with the spare module.

 

[markob]

Do you have another LH module to use as a test? Any LH module for M119 will work for a quick test, you're looking to see if the MAF stops glowing red all the time with the spare module.

I will attempt purchase one on EBAY today and test.