How many ohms for a N249

[tommy782]

Hi,

I want to test my N249 to see if she is in good shape. I want to know how ohms have suppose to have for a good reading.

thank

[walky_talky20]

About 30 Ohms. But if you really want to check it, the coil resistance only tells you half the story. The coil can be good (resistance checks out), but the solenoid can be stuck (corroded and unable to move). Or the coil can be good, solenoid moves (clicks), but it doesn't seal off the ports properly. To truly check it out, you'll need to actually operate the valve with a voltage supply and check the flow. It is a simple valve with 2 inputs and 1 output. The easiest way to check it is using vag-com output test mode, which will oscillate the valve open and closed repeatedly for you while you blow into the ports. By using this method, the most difficult part of the job would be disconnecting the 3 vacuum lines without breaking the valve (not too difficult), or stabbing yourself in the finger (more difficult).

That said, the N249's usefulness is a point of contention in itself. I feel that it is not necessary, but that is my opinion. The 1.8T's from 1997-1999 did just fine without it.

EDIT: Fixed, N249 not N75. Thanks oldguy.

[tommy782]

ok nice write up. what channel do you log in vagcom? why are you obligate to disconnect all the vacuum line when you just open and close the solenoid?

[A4SoftWalker]

This needs to stop.

A "Forum Search" using the words "N75+resistance" gave this

N75

Where I posted this information a few months ago.

People we can't keep on writing about the same stuff over and over and filling the servers with CRAP.

N75 Resistance Search

[old guy]

The question was asked about the N249. I believe walky-talky was actually referring to the N249 DV controller rather than the N75. He just wrote the wrong valve reference.

[walky_talky20]

Fixed. I apologize for the confusion. Won't happen again.

And you would use Vag-Com's "Output test mode" to aid in the checking of the valve. Same principle works for N75, N80, N112, etc.

[tommy782]

ok thanks,

[diagnosticator]

That said, the N249's usefulness is a point of contention in itself. I feel that it is not necessary, but that is my opinion. The 1.8T's from 1997-1999 did just fine without it..

The N249 is an important part for the correct operation of the engine management system as designed. Therefore, from that aspect the argument that it is not required is without merit. Without the N249, the engine management is functionally compromised and can not control the engine as intended. Consequently, it is not an optional component. Because of this fact, there is no basis for (unqualified*) arguments promoting that point. On the other hand, the argument that the engine management system is not optimally implemented with the inclusion of the N249 as a part of the overall control strategy is debatable, with the different system functional capabilities without the N249 understood and used as basis for argument.

(* Most of the arguments that exist, are made by unqualified sources.)

[walky_talky20]

I absolutely agree that the valve is designed to be there and the system is designed to work with it. I agree that it is a part of the designed operation of the system. Whether it is an *important* part is subject to debate, especially once you change other parts of the system - mainly the By-Pass Valve. Once that piece is changed, the control system should be adjusted for this change. Unfortunately, that is not an option for most of us.

I can only speak from experience, but I have seen the "N249 delete" alone (simply a re-routing of the related vacuum hoses) take long-term fuel trim values from +9% to within +/- 1%. This was due to the changing of the BPV and an inability to recalibrate the operational characteristics of the N249. In that case, the known-good N249 was causing very noticeable drivability and fuel-mileage issues. Not to say that in every case it is warranted to delete, but there are some. Having said that, the "usefulness" of electronic control over the BPV is certainly debatable, depending on what the goals are of course. For example, if simplicity and reliability is the only goal, it may be less desirable.