[dolemite]

I'm hoping someone around here has a solid background in electronics and might be of some help. Some of you know the solenoid board prices have jumped by 2-3x so I think it's time for those of us that are resourceful to come out of hiding and try to find ways around this absolutely ludicrous expense.

I had a variety of vanos-related codes for bank 1 from my '00 that has had a CEL for awhile. The car seemed to run 100% but I decided to replace the o-rings for that solenoid rack and test the individual solenoids in the process in hopes to eliminate the codes, don't have them handy.

Weeks ago, I used a 12v/2amp battery charger to test the individual solenoids via the pigtail leads using the handy diagram that another member kindly drew up (attached). I don't know definitively on polarity (or if it matters) but I used the purple and brown wires as common ground. Three of the solenoids worked fine and there was an audible clicking sound. When I tested the green wire (Solenoid 1 according to the diagram) it was sparking and seemed to be shorting out. I then tried testing at the solenoid itself and again was sparking and shorting, followed by a small plume of smoke that appeared to come from inside the solenoid... as far as I could tell. I figured the coil inside was toast and just finally gave out, or maybe I killed it. When I installed it back on the car it was running extremely rough. I drove it like this for a few weeks searching for the next plan of action.

I finally bought a replacement solenoid (just one) from Chris @ DrVanos (to the tune of $250) and had a good friend who does ECU repair install it last night. Install went well, I did not test the replacement from Chris although it appeared to be a used unit. I put it back in the car with new o-rings and fired it up and the car was back to running well again. Fantastic. I drove it for 15min down the street and back and then cleared the codes and fired it back up again and it was back to running rough again. F***. Frustrated, I drove home and crashed.

I pulled the solenoid rack this morning and tested again and found that the solenoid I replaced last night was again 'shorting' when applying 12v at the pigtail. I tested again at the solenoid itself, this time with a 5v/550ma signal from an old phone charger (after reading someone else's post about doing this) and nothing happened - no click or nothing... just some very small sparks at the soldering joints. I tested the other three solenoids and they worked fine using the same 5v signal.

The weirdest thing is I tested the OLD solenoid that I thought was bad directly with the 5v signal and I heard the piston moving this time. This made me suspicious that maybe the solenoid when soldered to the board in the circuit with the MOV may not work properly. Obviously the one that I thought was dead is in fact working fine.

I tried using a multimeter to check the impedance (ohms) at the solenoids but kept getting erratic results. I also tried testing the MOVs (metal oxide varistors) but got varied results; however, the first time I checked these the one in line with the solenoid that is not functioning was showing like 2-3 ohms and the others were 5-7 ohms so I'm starting to think that particular MOV is in fact FUBAR. I looked over all the other traces and could not find an issue. I know I can send it off to Chris (DrVanos) to check the whole board but it's my only car that I use on a daily basis.

My best theory: The first time I tested the solenoids I killed the MOV for the one I replaced. Still doesn't explain why the car ran momentarily last night.

Questions:
- Is there a way to check these MOVs on the board and get a solid notion that one or more are in fact bad?
- Does anyone know where I can find a replacement for the MOVs? If I can identify exactly what kind I need I'll just replace all four of them. I looked around on mouser.com but I have no idea what the specs are for the ones on the solenoid board.
- Another member mentioned the solenoids operate on 5v, not 12... thus the reason for the MOVs. If they are designed to limit the voltage (like a resistor) down to a usable current for the solenoids could they also cause the short that I am experiencing?

Thanks to whoever put together the drawing I attached for reference and thanks to Chris (DrVanos) for all your helpful and responsive emails.

 

[Sailor24]

Thanks for the extra info you know more than I do about electronics. You have the solenoid out by itself or is it still in the circuit? The only way to test parts is to have them separated, learned that the hard way. you must have at least one side of the solenoid free. Once you have one side out then when you do your ohms test you can measure the resistance of the MOV and a second test on the solenoid. I should also say I have a fuse on my 5v thingy mado.

As far as the parts, I know someone I can ask. He will know where to get them. I will need a picture to show him. He is the same guy who tried to explain to me those were not really resistors that they were what you said but said for my purposes they were resistors that shaped the corners of the wave. I don't really know what he is saying but he followed with it makes the corners square on the wave.??????????? I said no need to curse at me I just want more HP.

I think I know what your problem might be, found at least two places where some stray solder ended up. Look at the whole board very close with a magnifying glass and make sure that there is not a short somewhere on the board. With your old solenoid working now that it is out of the board something on the board must be shorted. You have the advanatge of following the known circuit to shorten your inspection. The wires could be pinched. Where the two wires from the solenoid got to the board was where I found one of the bad joints.

 

[gzig5]

That looks like my chicken scratch. You're welcome! :M5thumbs:

Sailor has it right. The components need one end lifted to reliably test them. I don't remember if an MOV can be tested with an Ohm meter or if you need something like a Huntron Tracker. You could always take the board to a local motor repair shop and they may have the equipment to test it. I find it odd that a bad MOV would take out the solenoid coil twice, but at the moment I am not in top deductive shape and nothing is beyond the realm of possibility with these cars. I wish I had a board to play with, I could use the equipment at work to characterize each component.
Greg

 

[Wurger]

My guess is that you have a broken connection between a solenoid and the tiny piece of circuit board that's attached to it. I have now had two instances of this happening in 6months, the broken wire still connects sometimes and will give irregular resistance readings. My engine also ran well 95% of the time with the broken wire...

Try to apply a tiny amount of pressure in different directions to the small pcb when reading the resistance value - if the reading changes, there is a bad connection. You might have this same problem in both the old and "new" solenoid. There is a way to fix this issue with a dremel and some wire if this turns out to be the cause :cheers:

 

[Sailor24]

Is there some reason we need to use the board? Why can"t we take the whole thing apart. Solder the MOV dodad across the solenoid and just connect the two wires to that. The board seems to be the foobar.

 

[jfoj]

Are you sure the MOV's are what are mounted on the board?

I have not read up on how he Vanos work, however, if the soleniod has DC applied only one direction, usually a diode is used in reverse polarity to clamp the high Voltage emitted by the coils magnetic field as it collapses.

They could possibly use a MOC or possibly a capacitor of some sort as well??

Do you know where the smoke came from on the unit while testing? Do you think it was the coil or possibly the "MOV" device?

If you could get a close up picture of the "MOV" device and possibly the solder joint this may be helpful in identifying what the part may be?

 

[josiahg52]

Typically an MOV is used to absorb current and voltage spikes like that would be seen during the collapse of the electromagnetic field of a coil or an ESD. They are typically non-conductive at the lower voltages (below their clamping voltage) and therefore should be observed to have a 'high' resistance.

A significant voltage or current spike can cause immediate failure of the MOV.

My experience shows that they are exceedingly difficult to troubleshoot. The MOV should have markings on it that can be looked up for specifications.

A free-wheeling diode is sometimes used in a similar application as an MOV. MOVs are cheap are generally more rugged and can be used in circuits that don't require precision. MOVs are of a conservative design and generally have higher ratings than a similarly packaged diode.

 

[gzig5]

Is there some reason we need to use the board? Why can"t we take the whole thing apart. Solder the MOV dodad across the solenoid and just connect the two wires to that. The board seems to be the foobar.

You could do that, but I think I would just direct wire everything while leaving the parts on the board. There is a lot of vibration in the system (hence all the failures for cracked traces and solenoid leads) so you don't want the parts bouncing around

 

[jfoj]

A common trick I use all the time in dealing with broken solder joints/circuit board traces is to use some stranded wire, 20-22 guage wire, to bridge the broken/weak solder joint(s).

Many times I try not to tin the entire length of stranded wire so there is some flexibility to deal with vibrations, bends, shock.

Long before printed circuit boards ever were on the scene, there was point to point wire!!

Good and bad depending on the situation.

Thermal cycling, vibrations, leadless solder are causing much more solder joint problems in many items. The leadless solder has a higher melting point, but it is also more brittle and less forgiving.

 

[Sailor24]

Personally I have no idea what the part is. I called an electrical engineer and tried to describe it over the phone. Electronics is not my strong point but electricity is not a problem. The term MOV came from the op who got that in one of the faq best guess.
The solenoids have very low resistance from memory 0 on the least sensitive scale. Truly when I look at solenoid it is open or closed so I may be wrong on what I remember about its resistance. If the meter jumps that usually good for me. I do remember that the combined circuit had a resistance of 4ohms. So what ever the device is it can't have a high resistance.
When I tested the the boards minus the solenoid I would have just been looking for a 0 ohms signifying a short so I don't even think I would have noticed the resistance of the part in question.
The part has markings the same as a resistors but is rectangular.

If I understand what you guys are saying if the part failed the solenoid would still fire?

 

[ard]

Is there some reason we need to use the board? Why can"t we take the whole thing apart. Solder the MOV dodad across the solenoid and just connect the two wires to that. The board seems to be the foobar.

I was thinking that yesterday when I yanked out both my solenoids for new orings.

The board does seem to be a weak link.

Just for convenience, I'd agree with gzig that you'd keep the boards to hold it all together, but replace the jumper wires with lengths that bypass any 'on board circuit traces'.

Mine are fine for now it seems.... but good info here.

A

 

[josiahg52]

The MOVs, or whatever they are (I personally have never looked or studied the circuit), should be wired in parallel to the coil of the solenoids IF their intended purpose is voltage and/or current spike supression. As I mentioned before, below their clamping voltage/current rating they will exhibit a very high resistance which, I can almost absolutely assure you the multimeter you used applied a voltage lower than that.

The coil resitance of the solenoid while likely low, should not be '0'. A zero ohm result would indicate a shorted coil or perhaps one of these devices. One thing to keep in mind is that an MOV will lose more and more of its effectiveness, or more pointedly its lifespan is reduced, with every transient supression or event in excess of its rating. Presumably, at some point they would need replaced.

The question is what are these things really. There should be some lettering or numbering on the side. Does anyone see these markings and can they provide them here?

 

[Sailor24]

Thanks I am starting to get it. I am sure they are not at zero either but for the purposes of my tests I never needed the resistance so never calibrated the meter or turned it to a sensitive setting. Step two was apply 5v and if it went click I was good to go. I did most of my diagnosis by how they sounded.Clean fast Clicks meant put it back in the car and avoid at all costs a $1200 rim job from my favorite dealer.

 

[Wurger]

I can positively affirm that both the solenoid circuit and a removed solenoid have resistance at 3,9-4 ohms. I know this because I have recently tested 8 solenoid circuits and all in all 12 individual solenoids, 5 of which were also tested when out of the circuit.

it is 4 ohms, and that is the resistance of the solenoid. Whatever the other component in the circuit is (capacitator/MOV/whatever), it is not having ANY effect on the reading.

proceed. :cheers:

 

[jfoj]

Useful info here.

I just ordered the soleniod O-ring kit from Dr. Vanos. I plan on pulling both my Vanos units in the next few weeks, cleaning, testing and replacing O-rings and will most likely put jumpers on all the solenoids to hopefully eliminate any future solder joint problems. Give the age of these cars and the heat and vibration they are subject to, I expect the solder joints may be getting toward failure.

I have never driven any other M5, so I do not know if my problem is unique, however, I have a lower RPM misfire/chuggle that happens under about 25-30% load up until about 2k RPM. After 2k RPM things appear fine. No CEL/MIL or codes showing up. The other day I tried to keep the car loaded and keep the misfire/chuggle going as long as I could to see if I could possibly get the CEL/MIL to trigger, but no dice.
I realize that there is a lot of discussion about cam sensors as well, however, I figured that it is cheaper to inspect and clean up the Vanos relay boards first and see if there is any improvement, then move on to the camshaft position sensors if needed.

I also have a Fluke Scope meter I may use to check the cam sensors before I wholesale replace them all. Given the car has 2 of each type of cam sensor, if I can get my Scope meter to monitor the signals, I may be able to identify a quesitonable sensor by comparing the output signals to others.

I will report back anything I find during my clean up, inspection and repair if I find anything of interest.

 

[dolemite]

Well, you fellas are not going to believe this. The problem is gone, and worse - mysteriously. I had TONS of codes - misfires, vanos r*tard valves, O2s, etc. All of them gone. I must have somehow found my way into the good graces of the BMW gods.

I was about to put the solenoid rack back in the car Saturday night after calling every electronics repair center I could find in Charlotte to no avail. I started to think... maybe there's another issue. I studied the board with a magnifying glass and found no real noticeable spots where the traces looked cracked or suspect... nor any of the solder joints. I tried getting some readings w/ my multi from a couple spots and didn't really come to any solid conclusions. I scraped a few spots between solder joints where it looked like remnants of flux just to make sure there was no contact. I must've spent an hour on this thing. Nothing.

When I was about to put it back in the car (with the new OEM o-rings I had swapped the other day) I noticed how little clearance there was between the square aluminum cover (mine is an 11/99 build date so it has the old cover w/o the pretensioned allen screws 'behind' the solenoids) and the small PCBs (printed circuit board) where both the solenoid and yellow+black wires are soldered to connect. I also noticed the small yellow wire from the pigtail/harness was slightly frayed close to where it was soldered to the solenoid board. I looked at the cover and wondered if the center screw housing had been rubbing or was grounding out against that wire, it looked as if it could be touching but hard to tell w/o seeing inside when the cover is on. I put a little heat shrink tubing over the wire close to the board to ensure this wasn't an issue.

Back to what I was saying - the little sections of PCB where the solenoids and black+yellow wires are soldered to, if not rotated to a certain position when installed, looked as if there could be contact w/ the cover. Not sure if the cover is grounded or not, but I would assume so. It is fairly easy to rotate the solenoids themselves even when pressed into the VANOS unit, obviously thus the reason for the length of the black and yellow wires. Anyways, I did rotate the two solenoids that were closest to the pigtail towards the middle of the board to ensure that there would be no possibility of contact with the cover. Again, I don't know for sure if there is a possibility for contact there, but better be safe than sorry. So, basically, the solenoids are turned to the point where the black+yellow wires from the board to the solenoid PCB are at full 'extension' wrapped around the solenoid. I also turned the top two more towards the center to avoid the potential for electrical contact as well.

Trust me - I'm ecstatic the problem is resolved, but I wish I knew exactly what happened here, or what I did exactly to avoid a repeat issue. Here's what still doesn't make sense:
- How did the old solenoid I replaced test fine OFF the board but didn't 'click' when using 5v directly at the contacts?
- A related question to the above, why is it that when applying 12v to the green & brown wires (C1 in the diagram) causes a spark that appears to signify a short to the same solenoid I replaced -- this was the case for both the old (previously assumed to be bad yet tested good OFF the board) AND the new solenoid?
- 5v applied directly to the contacts of the new solenoid after it was soldered to the small PCB connector did nothing. The other solenoids would click in similar fashion to the way they would when I applied 12v to the other three would when using the pigtail connectors.

It would seem like there is some kind of an issue testing the one solenoid on the bottom right (if you're looking at the board from the back of the solenoids, when the pigtail is on the bottom) WHEN it's connected to the board...

 

[Sailor24]

Best guess that yellow wire that was frayed was doing you in. They can get pinched on removal. I did that twice, the second time I did my best not to, but still did. Glad it all worked out for you. You definitely had a short only thing that explains it. Then again maybe you are right BMW Gods, best go pray just to be safe.

 

[paul88]

Where do I purchase the MOV?

 

[sikessr]

Where do I purchase the MOV?

Did anyone ever figure this out??

 

[sikessr]

Did anyone ever figure this out??

You can order them from Dr. Vanos for $10 each, I just got off the phone with him.