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MEI VN2500 bill validator not accepting bills

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does not even pull them in at all even though power seems to be on

Just acquired a dixie narco series II soda can machine at work. it has eight soda choices. Three are wide, five singles, three deep each. After replacing a honing switch next to one of the soda motors, I basically have all eight sodas working and all are priced at 75 cents

So the MEI vn2511 bill validator is not working properly. The red light is on and steady, which should mean that power is on and there are no problems. The two green arrows (compact bezel) are flashing on the outside of the bezel to attract people to insert their dollars. Problem is that putting a dollar in the slot does nothing at all (although green arrows go out). It doesn't even suck it in a little and reject it.


Looking in the back side, it doesn't look like the wheels are spinning. When I remove the LED housing and put it back in, the wheels do spin some as they reset (?). Last night I also folded a bill in half the long way and slid it in past the first set of wheels and the wheels started to spin backwards to reject it. So I think I know the bill motors are working. I also know that some if not all the optics are working.

I'm concerned if the very first set of optics that detect that a bill is in the slot are working. There are two pairs - top and bottom each side. I cleaned all lenses. there was also gunk on the lower white idle wheels so I cleaned them up too. When I put a bill in the slot, even though the wheels don't suck it in, the green lights go out and the power light goes out as well, only to turn back on shortly after I remove the bill.

just as a test I removed the whole unit so I could get to the switch settings. It was on 4-way acceptance, high security but I switched it to high acceptance thinking that might help (we don't have any kids messing around here), and set to accept $1 bills only. I'm not sure what pulse timing is but it is still on the factory default of short pulse.

the machine's control panel only has two red buttons (set-up and diagnostic). Not knowing what they do, I haven't touched them.

While cleaning I made a little progress. Somehow I got it to pull one bill in, even though it rejected it after a few seconds and I only got to do it once. So at least I know the motor wheels and belts are working like I think they should. And back to the pull sensor, I think it is partially working cause every time I put a bill in the slot, the green flashing arrows stop flashing, so it must know that something is there, right? I folded a bill in half and put it in the right side, then the left and it seemed to detect that something was there both times so I take it that they are both sensing. So, maybe there is some logic problem that is not telling the motor to start pulling once the pull-sensor sees that a bill is in the slot.

re-reading some of the other issues that people have had...My change collector is well stocked with all three coin types. It gives proper change of nickels, dimes, or quarters when I put various amounts in such as 80, 85, 100 cents when a vend costs 75 cents. I also found some dip switches on the change collector but did not touch them. they were labeled with such things as "25cent highest coin" and "accept dollar coins" and so on. As far as I know, if the bill validator worked in the past, it was with these same settings. I should find out from the prior operators at what point the validator stopped working if I can.

my next steps are to clean clean clean with rubbing alcohol since simple damp cloths don't help. I will also pull down the harnesses and check the continuity of each wire with a mutli-meter.

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I don't think I'm there yet .  Besides, until I figure out what is wrong, how do I know that another VN 2500 won't have them same problem in the same machine.

I'm not in a total bind yet though.  I also have a snack machine right next to this soda machine.  I put up a small sign so the guys here know that if they want a soda and only have a dollar bill, to put the bill in the snack machine and hit the change button to get four quarters that can then be used to buy soda.  The only small hassle is making sure the snack machine is stocked with quarters, no biggie.

I just checked the continuity of each wire on the harness and everything checks out.  I'll be putting the validator back in the soda machine tomorrow.

If it doesn't work and I get no additional advice, my next step might be to get a price quote for repair from GEKAY Sales & Service in MA.  Their sticker is on the validator from a repair they did in the 90s.  Maybe they will be the cheapest option.

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Welcome to the board. Where are you located?

You may also want to send a PM to Technivend here on the board and invite him to respond to your question. He is our resident full line repair guy!

Here is a link to his profile...


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Sorry for the late reply. I never got notification of a PM in my email.

I have a few questions if you are still playing with this.

Sounds like you have this in a Dixie Soda machine. Yes?

What type of interface are you using, serial or MDB?

What type of snack machine do you have next to it and what type of validator is in that machine?

Have you tried swapping out the coin mech?

Based on your diagnostic steps (which are very thorough) it does sound like an issue in the validator but we really do want to rule out any other possibility. Remember, the validator in the machine for the most part are stupid and just want to take in and validate bills. It is left up to the machines logic to tell the validator if it should or should not accept the bill.

If it is a Dixie with an SII board you must pull the interlock switch out when testing with the door open or you will get a disabled from the VMC error. This is normal and a correct function. Now we need to be sure the machine wants to let the validator accept the bills. Depending on the board we may need to check the validator acceptance settings or the coin mech my not be sending a proper signal to the VMC.

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Thanks for helping Technivend.  So far, people have been using the snack machine as a change machine as requested by my sign so I've been selling a good deal of soda.

Okay, it is a Dixie Narco series II soda machine.

How do I know about the serial or MDB interface?  By the harness type?

The snack machine (a Snackshop 4000) has a different MEI Validator.  It is a VFM1- L1.  The harnesses look different so I haven't tried interchanging them, if that is even possible.  I have another Dixie Narco Soda machine, an older one, that also has one of these MEI VFMI validators that is working too.  It is just the VN2500 that isn't working.

Well, as far as accepting bills logic goes, I don't think I am even getting to that step in the logic.  It is failing to even "pull" the bill in at all.

What is VMC (it is not in the glossary)?  And where is the interlock switch?

I've tried both "high security" and "high acceptance" with no improvement.  I haven't played around with the other dip switches on the DBV or the Coin Mech.  And I have not touched the two red buttons (set-up and diagnostic) on the SII board since I haven't been able to find any guide on how they work.

Thanks again for the input.  I'll be away for a week staring Saturday.  I'll be sure to have the Snack Machine's Coin Mech stocked full of quarters :)

BTW, Caserri, I am in NYC.

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According to  my charts your VN2500 should use a 110 volt standard Mars hookup. The VFM1 is also a 110 volt validator. In theory the VFM should be able to work in the Dixie. Of course the AP4000 never came from the factory with a validator in it so you do have some sort of kit in it and some of them had very strange interfaces. Obviously, it would be easiest if we had a known good validator to test in the machine or another machine to try your VN in.

If you are telling us the harnessing is different then you cannot swap the validators around in that location. Do you have other machines that you may be able to test the validator in? Do you have any spare valdiators you can try in the machine (ie Coinco)? The VN2511 being 110 volts rules out an MDB hookup so a Coinco BA/MAG30SA should work as well.

The interlock switch is located on the door above the coin acceptor and is a white switch. VMC stands for Vending Machine Controller and is a term that Mars uses on their diagnostics.

Did this validator ever work? DId you get the machine this way? Depending on the interface the VN can use either a harness that plugs directly into the control board of the machine, just use the 9 pin white connector, or use the 9 pin connector with an 18 pin connector together. If you can email me some pictures of the interface it may help.

I hate to say it but you may be at the point of having to send your unit out to be tested. Even though some of your customers are using the snack as change you more then likely are losing some sales without the validator working in the snack.

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I have an AP435 that uses a VFM1 that I changed to a VN2500 that worked, so you can hook up the 2500 in the 4000 to see if it works.Hope this helps.


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you guys are right (of course), re-examining the harnesses and ports I see that the VN2511 and the VFM1 are interchangeable. I can see that the AP4000 snackshop's DBV was modified, the DBV being where there used to be the 'G' row gum selection window.  Anyway, it's DBV is hard to get to behind the service buttons.  So the easier option is to take the VFM! out of the older Dixie Narco across the plant.  I'll just swap them temporarily to see how the VN2500 works over there and it's VFM1 works in the SII.  Obviously if the VN2511 doesn't work in the other machine, I'll swap back since the other machine doesn't have an adjacent "changemaker" like the SII does.


I share your feeling (Technivend) that I will probably end up sending the VN2511 out.  I really doubt it will work in the other machine.

Funny thing was, playing around with the VN2511 in it's SII, I was unplugging the SII power whenever messing with the VN2500's plugs.  Well, since it is already essentially broken, I unplugged and replugged the 10-pin harness going into the control board, and the 9-pin plug as well while the SII was still powered up.  After replugging the 9-pin, it pulled the next dollar in all the way ("YAHOO!") only to reject it after a few seconds.  Then I couldn't get it to pull again, even after repeating my action of unplugging and replugging the 9-pin ("damn").

I see the white interlock switch.  When I close the door, it gets pushed in and the digital display shows "...." for a moment.  I never noticed any difference in how the machine operates for me with the door open.  DBV obviously doesn't work any better.  Today, I taped the white switch down while working but noticed no change/improvement except for that one moment above.

I don't know the last time this VN2511 worked.  I did adopt the machines this way just a few weeks ago.

"Depending on the interface the VN can use either a harness that plugs directly into the control board of the machine, just use the 9 pin white connector, or use the 9 pin connector with an 18 pin connector together. If you can email me some pictures of the interface it may help."

---yes, now that I took a closer look, a 10-pin comes out of the VMC and splits to a (8-pin? i think) plug that is just hanging there.  Down the line is another split.  One splits to the 9-pin that goes to the lower of two plugs on the side of the VN2511,  the other split goes straight into the 18-pin.

is there anywhere that I can get more infomation an how to operate the SII VMC?  I still haven't pressed either red button.

Machines are fully stocked, including their change dispensers.  I won't be back for a full week.  When I return I will do the VN2511 / VFMI swap just to verify that it is the VN2511 alone that is failing and not the SII.  I'll take some pictures too.  thank you.

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