I need help diagnosing my National 797 combo machine

[timlitw]

the one of the soda vending slots will not vend.  If I test the slot from the console it works fine.  This is my first / only machine and I don't have a repair manual as I bought it used.

 

So any links to a diagnostic manual would be welcomed.

[AngryChris]

I'm not familiar with that particular machine off the top of my head, but some of those combo machines won't even allow you to vend a selection unless there is a can already in there.  WIth that said, it shouldn't even allow you to test-vend it if that's the case.  I don't know how the sold-out process works with those combo machines, but I would venture to say that your sold-out switch is defective.

 

If it's your first machine though... it's tough to say.  Worst case scenario, you can try to call some local vendors and ask them if they will repair your machine for cheap (meaning, $50/hour or less).  If you tell them the model number (national 797) and the problem (soda selection not vending, might be the motor/switch), they might be able to come out and diagnose/fix it.  I think you would be looking at $150-$200 to have a company come out and fix it but that machine might be worth it if you have a location for it.

 

You could also simply not use that selection.  It looks tacky, but it won't cost you any more money.

 

The first thing to do is to make sure you have enough cans in it (possibly as many as 3 or 4) to trigger the switch and rule out the possibility that you didn't have enough cans in it to make it vend.

[moondog]

the one of the soda vending slots will not vend.  If I test the slot from the console it works fine.  This is my first / only machine and I don't have a repair manual as I bought it used.

 

So any links to a diagnostic manual would be welcomed.

Here's the manual http://www.dsvendinginc.com/pdf-manuals/nv18.pdf.  I have a couple of the 474 combos - they're older than yours but appear to have the same soda box.  You can repair the ejector mechanisms on these but from your description, I'm not sure that's your problem.  A broken ejector wouldn't work in "test vend"

[AZVendor]

Make sure you actually have a price set for that selection by entering that selection number into the keypad with no money inserted beforehand in the machine.  What does the machine then say on the display when you then try to buy that selection with money?   When you open the door do you get any beeps and an error code on the display such as ERR X where X is the tray number associated with the problem selections?  You could have a bad vend motor that won't communicate properly, a bad diode board below the can module, a bad connection at the diode board or the snack driver board.  If you have a bad sold out switch, the selection will either vend when there is no product in the column or it will show sold out when the column has 2 or more cans in it.

[timlitw]

Thanks for the suggestions

Make sure you actually have a price set for that selection by entering that selection number into the keypad with no money inserted beforehand in the machine.  What does the machine then say on the display when you then try to buy that selection with money?   When you open the door do you get any beeps and an error code on the display such as ERR X where X is the tray number associated with the problem selections?  You could have a bad vend motor that won't communicate properly, a bad diode board below the can module, a bad connection at the diode board or the snack driver board.  If you have a bad sold out switch, the selection will either vend when there is no product in the column or it will show sold out when the column has 2 or more cans in it.

Ok, tried these.  It shows the correct price when I try the selection without money, when I try with money it says make another selection.  So I decided to take the cans out and leave that one empty till I find parts or decide what to do.  

 

Then when the other slot didn't have room for all the cans I put the remaining ones back in that slot and now it works.  So I guess it is fixed and I'll have to double check it the next few weeks to see if it keeps working.

[AZVendor]

You might have a faulty door interlock switch that isn't forcing the board to scan all selections after closing your door.  You might also have a bad sold out switch that is simply not telling the machine that the product is in the column.  There is a lever that the second can lifts up as it rolls under it, activating the sold out switch.  There could be corrosion on the switch contacts making it intermittent.

[timlitw]

You might have a faulty door interlock switch that isn't forcing the board to scan all selections after closing your door.  You might also have a bad sold out switch that is simply not telling the machine that the product is in the column.  There is a lever that the second can lifts up as it rolls under it, activating the sold out switch.  There could be corrosion on the switch contacts making it intermittent.

 

Thanks, I've worked on electronics on and off for years so I'll see if this is something I can fix.

[chris in bc]

Have you had a can explode in there lately?

[timlitw]

Have you had a can explode in there lately?

 

I don't think so, there is no sticky mess.