MAP Sensor Bosch Type 3 Mercedes 450SE Question

Hi Dr. D-Jet and thank you for approving my membership. I have a 450SE with the type 3 Bosch Map sensor. I measured the primary inductance (spec calls 80-120) and got 124.5 on my DMM.

Is this acceptable? Will the MAP sensor work? Could it have mal-adjusted? (the black cap has been removed)

Hi coil inductance was 365 and the MAP sensor held vacuum.

Thanks

Hi Martin,

it would be great if you sign with your first name, then it is easier to greet you.

well it is hard to say. You know that 90 Ohms is what it should be and that tolerance is 80 -120 Ohm (named by Bosch and Mercedes-Benz). 124 Ohm could mean additional tolerance of your Ohm meter, your measuring cables and ... So I would not worry too much. Main thing is that no one opened the black cap to "tune" it.

Hope that helps,

Hi Dr D-Jet

The cover is missing so someone most likely tried to tune it.
that's why I was wondering if the tuning changes the coil impedance.

I don't know what tuning it does. If I assume that's it's changing the coils location with respect to the transformer's metal core, it would change inductance and possibly resistance measurements as well.

Thanks

Marty

Hi Marty,

tuning does not change the resistance of both coil windings. It changes position of armature shaft.

Hi Marty,

to be more deitaled: MAP sensor is like a variable transformer. A transformer has 2 windiings which always stay the same. The position of the ferromagnetic steel shaft inside the core changes and thus changes tranformed voltage. That causes different coltage levels in ECU and therefore a broader or smaller basic injection pulse.

If you were located in good old Europe I would offer to quickly readjust and verify your MAP sensor. But transportation and customs formailities is too diificult with the US I am sorry. Adjustment screw is rather senisitve, even ithat in type 3 MAP sensor it only shifts the curve parallel up or down. The real mess with those MAP sensors is that they can be easily detuned and that I have to verify them twice: Once with a defined environental pressure and onve with a high altitude pressure to also check altitude compensation.

Volker wrote: Hi Marty,

The real mess with those MAP sensors is that they can be easily detuned and that I have to verify them twice: Once with a defined environental pressure and onvc with a high altitude pressure to also check altitude compensation.

Sounds like a good reason to take a trip to the mountains. Thanks for your help.

Marty