I thought those were diodes even though from the pictures they indeed look like resistors. Diodes can easily short out after years and years of shunting high voltage spikes when the solenoids turn off. Their function is simply to protect the driver circuitry in the DME. You will want to replace the missing components for sure. If it were me, I would replace the diodes with 1N4007 devices. Be sure to observe polarity or they will short out again. The end (of the diode) with the banding will connect to the (+) lead of the solenoid, otherwise it will short again and nothing will work. Oddly, I believe the black wire on the solenoids is the (+) on these cars.

-James

 

Interesting. If a diode fails, does it short or break? Time to find out.

The components didn't fall off with it in my hands, there is nothing there, but it looks like there was at some time - maybe they got damaged during removal? If they are diodes I don't see how that could be causing the problem, but I will trace things around and see what I come up with.

 

The first thing you need to know is those are not resistors they are MOVs. Since you have a real hard time sourcing MOVs, we replace them with diodes. Search Gzig's handle and MOVs or diodes or both he listed the right diode and how to install them. If that fails use 68FB as the handle. The way a MOV fails is why you are not getting any power to the solenoid it is sort of their job.
When testing these things(noids) it does matter what volts you supply sort of. Don't supply more than 2.5 watts if above 5-6 volts. I am not going to try and explain it(failed too many times) but if you supply the noids with 12v at over 2.5 watts as constant power the odds are you will burn or damage the winding inside the noid. There is a duty cycle on these devices they are not rated for constant volts. We must supply them with constant volts to work on them so use the lowest you can.

 

Sailor, do you know what voltage and current the stock ECU supplies? I have my Motec ECU setup to use half-bridges as high-side triggers for the vanos solenoids, but am wondering at what level to set the actuator reference voltage. I can choose anything from 5v to 16v.

--Peter

 

Diodes can fail in both modes (open and short) however the most common failure mode is shorted. If enough current passes through a shorted diode then it simply explodes (pops) off the board or breaks in half. I'm 99.9% sure the black wire to the solenoids is the positive so be sure to connect the power supply this way.

 

It is starting to make sense now. I am not using anything approaching high power, but I will back it off to 6v.

Thanks.

 

Interesting, as to my understanding (recent reading) solenoids rarely burn out so as you said i suspected the board to be at fault somewhere. Im also wondering how those diodes disappeared. The VANOS system looked like it had never been taken apart before so im wondering how this happened. Maybe Sailor can chime in and give some feedback.

 

Found it - http://www.m5board.com/vbulletin/e3...-e52-z8-discussion/197826-vanos-problems-could-use-some-help-2.html#post2209359

Looks like it is a 1N4148 diode (I need to figure out the exact part number, thre are several) and they are pretty easy to find.

 

Good luck boys you will be very impressed with yourselves when you are done and they work. Thank you guys for making me see something I have yet to see. If a MOV fails the codes reported will be the same as noids that have a reduced flow from crud.

 

I doubt that hiha. Sort of like no flow from crud

In this application, they are probably flyback diodes. Essentially the same - prevent damage to the DME and control voltage spikes.

Yes, it can be generalized that MOV's and flyback diodes serve a similar function but an MOV is a device that does far more than a simple flyback diode does and typically have a longer service life in severe conditions in the same application. A flyback diode will prevent reverse current resulting from the voltage induced in the solenoid coil after the solenoid is deenergized from being fed back into the dirve circuit but an MOV will also absorb transient voltages while the circuit is turned on, perhaps extending the service life of downstream components. I am very interested in what you find.

I'm no EE. Unless someone can give me a spec for a MOV and where to buy one I will have to stick with the diode mentioned above. I'd like to replace what was there with the same thing, but I don't' know enough to know what to use :sad1:

Thanks for the help

 

In this application, they are probably flyback diodes. Essentially the same - prevent damage to the DME and control voltage spikes.

 

Yes, it can be generalized that MOV's and flyback diodes serve a similar function but an MOV is a device that does far more than a simple flyback diode does and typically have a longer service life in severe conditions in the same application. A flyback diode will prevent reverse current resulting from the voltage induced in the solenoid coil after the solenoid is deenergized from being fed back into the dirve circuit but an MOV will also absorb transient voltages while the circuit is turned on, perhaps extending the service life of downstream components. I am very interested in what you find.

 

+1. If they are MOVs, I wonder how the circuit characteristics will change since the built in capacitance will be lost/greatly diminished with a typical diode.

 

Good luck specing the MOV and if you get help doing so I've had good luck with Digikey.com sourcing parts. Diodes should suffice being as you've made it awhile with absolutely nothing on two solenoids. I'd venture to say the DME probably carries some output protection internally.

 

Found them.

Minion, you owe me $7.00 - pay up or else ouich

 

Thats a little steep. I don't know if i can afford that. cherrsagai

How are things going with it? I hear working with these solenoid boards is about as easy as changing a tire.:grinyes:

 

The diodes will be here mid-week, so I hope to have the boards back in shape next weekend

 

I had this same issue. Ended up following Gregs advice and also following the image below from a fellow member. I used diodes from my local radio shack 1N4148 (part number). I removed all oem MOVs and soldered new diodes to both boards.

 

i was allready lost after the first pic :grinyes: electrician is not my calling thats for sure


hope you guys find a good fix for these damn boards..two thumbs up for the solenoid doctors :cheers:

 

Putting them on the solenoids will make the job a lot easier

 

So..
Cutting the end of a home cell phone charger and using the ends to power the solenoids and clean them is a bad idea?
That's what me and Rhino did when we needed to power the noids.. Is a home a/c outlet too much voltage for the board?
Didn't leave the power source on for more that half a second tho.. more like tapped the positive wire of the charger to the + side quickly + repeatedly..

 

The 120 Volts AC that comes out directly from a wall socket is too much for the solenoids.

The transformed and rectified 3.6 Volts DC that came out of the cell phone charger is fine.

 

Ok so the cell phone charger converts the 120 ac to 3.6 dc..
Sweet. I'm gonna ghetto rig another cell phone charger so I can do this again when I need to.. lol

 

That is what I use, mine is a 5v charger that puts out 500ma.

 

You can just buy a $3 6 volt battery that is used in one of those big
Flashlights and is available at any store.

 

You can just buy a $3 6 volt battery that is used in one of those big
Flashlights and is available at any store.

True. I have an Eveready 12V "Lantern Battery" with the screw-on terminals that I bought at Radio Shack when I was in high school that I still use for temporary power and testing various circuits, lights, relays, etc. I consider a requirement on my work bench. If I need less voltage I just put some resistors in series with the load. Still reads 12.1 VDC even after all these years and thousands and thousands of miles as I moved around all over the country.

And the 3.6 V charger was a typical and common one and I made an assumption. There are certainly others out there and I can't say which one was used in the past or if 3.6 VDC is enough to operate the solenoids.

 

Probably a bit irrelevant now that you have found the fix but post #23 onwards provides some more insight to the diode issue. I don't know the difference between an SM4007 diode and the 1N4148 one recommended above.

http://www.m5board.com/vbulletin/e3...iscussion/200341-june-1999-e39-m5-misfire-bank-2-requesting-your-expertise.html

 

Probably a bit irrelevant now that you have found the fix but post #23 onwards provides some more insight to the diode issue. I don't know the difference between an SM4007 diode and the 1N4148 one recommended above.

http://www.m5board.com/vbulletin/e3...iscussion/200341-june-1999-e39-m5-misfire-bank-2-requesting-your-expertise.html

1n4148: high speed 4ms (typ.)
100v max reverse voltage
450mA forward current

4007 series: 1000v max reverse voltage
1A forward current

Basically the 4148 is a faster recovery diode but the 4007 is higher rated as far as voltage and current. Either should work fine for this application. Not sure of what voltage level the solenoids spike when turned off but I imagine it is greater than 100v. There are probably even better diodes available, like those used in switching power supplies (both fast and high voltage rated) but I don't know part #s right off hand and aren't really necessary here.

 

OK, while waiting for the diodes to arrive I de-soldered the blown diodes from the one board and now all of the solenoids work from all of the junction points

I understand now that the yellow wire is negative and the black wire is negative, the circuit bears this out sicne the positive is distributed to all of the solenoids and the negative is used by the DME to trigger them, very typical. Why in the world they chose those colors is one of those German mysteries

From What I understand the diode needs to go with the BLACK BAND end on the Positive (which is the black wire) and the other end to the Negative (which is the yellow wire) - is this correct?

Thanks.

 

I am totally confused about how WDS shows the VANOS circuits.
I confirmed on my car the pinout for the DME side of the VANOS connector is as shown in WDS below:
Pin 1: green/black (SW/GN).
Pin 2: brown/black (SW/BR).
Pin 3: black (SW).
Pin 4: red/black (SW/RT)
Pin 5: brown/black (SW/BR)
Pin 6: yellow/black (SW/GE).

But this diagram seems to be WRONG! The top grey boxes labelled “VANOS valve cylinders 1-4” and “VANOS valve cylinders 5-8” are nothing like the solenoid coils and diodes that are on the boards. They look more like typical DME schematics, with the switching transistors switching keyed 12V power (terminal 15) on and off.

This other diagram in WDS below also seems to be incorrect as it shows the DME supplying steady (not switched) 12V power through 4 wires to the VANOS board. It does however show the remaining 2 wires going to ground, which they do.

So what is correct? Based on gzig’s schematic below, it seems logical to assume the DME is supplying a PWM’d +12V signal to each of the 4 solenoids, with 2 solenoids sharing a common ground. But neither of the above diagrams reflects this. Can anyone shed any light on this?

 

I certainly have not figured out exactly what they have done and described it both ways so far. This is the way I would have expected it from OBDII experience. Power should be constant and the DME should get the control of the grnd. 1 reason for this is simple, that is the way OBDII requires circuits to work. Manufacturers can ask for changes as long as some criteria is met. I have not had a problem so far I have always replaced a MOV(if that is really what they are) with a Mov. I only have about 6 left so might be time to find out for sure.
You measured this and showed a switched 14V???? I don't remember exactly how I did it the one time I measured and got close to 5v which is what I expected because of OBDII. That was at one week with this car so.... I could have given myself the answer I was looking for.
As far as the gray box don't believe them, somewhere in the WDS there is a disclaimer telling you the same.

 

I agree the DME controls a lot of stuff like the injectors and coils by grounding the +12V supply but all my tinkering with the VANOS solenoids has convinced me the DME PMW's the +12V supply and the ground is constant. Maybe the OBDII rules don't apply so strictly because it is a non-standard manufacturer-specific system.

I have seen some stuff supplied with 5V in WDS (TPS, CKPS) but BMW seems to favour 12V.