Professional Carwashing & Detailing

Efficiently troubleshooting coin-operated vacuums

October 11, 2010

Having kicked myself more than once for wasting time investigating problems with equipment, I thought I would share what I believe to be an efficient way for troubleshooting problems with coin-operated vacuums.

The basic premise for troubleshooting is to check the simplest things first. Problems fall into two general categories:

  1. The vacuum turns on but there is little or no suction at the nozzle.
  2. The proper number of coins is inserted, but nothing happens.

After determining the general category of the problem, you can proceed through the rest of our troubleshooting list.

Scenario #1: The vacuum turns on but there is little or no suction at the nozzle

1. Check nozzle for obstruction.
Remove foreign objects or particles. If no obstruction is found, continue to the next direction.

2. Visually check to make sure the clean-out door is closed properly.
I have experienced customer complaints after someone left the door open or it was not latched properly. Some people install locks on the clean out doors. I have tried this, but the end result is the latches and hinges are broken when people need to retrieve jewelry or money.

If an open clean-out door is a recurring problem, use nylon zip ties to keep it closed. These tend to keep the people looking for loose change out, but allow easy access for more serious issues.

3. Remove hose from body of vacuum and see if there is suction at hose connection.
You should visually check the hose for obstruction and use a probe to make sure nothing is stuck a little further in.

If there is no suction, remove the clog in the hose by shaking, or using water or compressed air. I keep a spare hose to change out any clogged hoses so the vacuum is not out of service while I work on the hose.

If the hose is flushed with water I prefer to let it dry before reuse since a wet hose will cause dirt to stick to the interior and moisture sucked onto the filter bags turns dirt into mud adversely affecting the suction. (In cold weather the moisture will freeze on the bag adversely affecting suction.) The hose can dry over time, be flushed with compressed air or held up to your automatic or tunnel blowers if you have them.

4. Make sure there is a good seal at the clean out door.
It is easy to check by running a piece of tissue paper around the edge of the door while the vacuum is running. The tissue should not be sucked toward the door. If the seal is bad you may need a new one. They are available from your equipment supplier. A simple alternative is to use foam self-sticking insulation sold at home centers. Clean the interior perimeter of the door and apply the insulation.

5. Check motor.
If you have a two or three-motor vacuum, it is possible one of the motors is broken. If your vacuum has a door where you can see or access the underside of the motor, make sure any screen below the motor opening is not clogged.

If it is clogged, you most likely have a bad or improperly sealed filter bag. If the screen is not clogged, turn on the vacuum and use a piece of paper to check to make sure each unit has suction.

CAUTION: If there is no screen, don’t use this method. There is a risk anything you use may be pulled in to the motor and cause damage or injury.

If you cannot access the motor intakes from underneath, you will need to remove the dome and with the clean-out door open start the vacuum. Any bad motor will not rotate. If you leave the clean-out door closed, the bad motor(s) may rotate due to suction from the other motor which will mislead you into thinking the faulty motors are good.

If you find a faulty motor, replace it, but make sure that the exhaust ports are not clogged with debris. If they are, your filter bags are either installed incorrectly or have a hole allowing debris to pass into the motors. A new motor installed without addressing this problem will fail quickly.

You should also check any screens below the intakes for large holes. Some vacuums do not have such screens, but it is a good idea to have them as a secondary line of defense if a filter fails. I have saved a few motors when they were making a lot of noise due to debris in the exhaust ports. I pull out whatever I can by hand and use compressed air to blow out the rest.

6. When all else fails…
If there are good seals, no obstructions, and all the motors are working then you will need to clean the filter bags. Shaking them will sometimes loosen some debris, but if they have gotten so bad that they severely impair the suction, I recommend they be removed for a thorough shaking, washing and drying.

By holding the bag inside a garbage can and shaking it, most of the debris stays in the can instead of going all over the carwash lot. Again, I keep a spare set of filter bags on hand so that the spare can be installed while I clean the others and let them dry thoroughly.

Scenario #2: The proper number of coins is inserted, but nothing (allegedly) happens

First things first, deposit coins yourself to see if this report is accurate. Few things are as frustrating as troubleshooting to learn the complaint was based upon depositing the wrong number or type of coins.

However, on occasion there is a problem where a unit will “miss” a coin periodically, and repeated complaints will need to be investigated. My general rule of thumb is that if it works correctly four times in a row, it does not warrant further investigation. If the proper number of coins is inserted, but nothing happens, continue with the following steps.

1. Check to make sure the circuit breaker controlling the unit is in the “on” position.
The next frustrating item is to learn someone accidentally turned off a circuit breaker — or forgot to turn it on as the case may be. If the breaker is in the “off” position, caution needs to be exercised to determine it did not trip due to a mechanical problem. After turning on the breaker you need to let the unit run through a full cycle to see if it happens again.

If the breaker trips again:
a. Visually inspect all wires and connections for a bad connection or burnt wire. Correct as appropriate. If there are no apparent visible issues, then;
b. Disconnect one motor at a time and re-test to see if breaker still trips. This will reveal a bad motor. If breaker still trips and all motors are replaced, try;
c. Changing out the timer, relay and transformer. Test after each change out. If breaker still trips, then;
d. You — or a qualified technician — will need to determine where the problem lies by tracing all elements of the circuit.

2. Check the coin mechanism.
Your first step is to make sure coins are falling through as they should. If this appears to be happening correctly then, make sure all wires from the coin acceptor are properly connected.

To check the coin acceptor, use a short wire to touch the “coin switch terminals” on the timer and provide the required number of coin pulses. If the vacuum starts it shows you have a bad coin acceptor.

If your vacuum unit has a mechanical coin switch, you should check that there is continuity from the switch terminals when the switch is activated. If not, change the coin switch or acceptor.

3. Check the access timer.
First, use a voltage meter to make sure there is power to the timer. This may be 110 volt or 24 volt depending on the unit.

If there is no power to the timer you will need to check the next closest location to the timer that should have power. If it is set for 24 volt operation, locate the transformer and see if there is power entering and exiting the transformer. If it enters but does not exit, replace the transformer.

If there is no power entering the transformer, the supply wires will need to be traced back to the next closest junction to test for power and proper connection at that point. If they cannot be traced to a point where there is power a qualified technician may need to open the breaker box to make sure power is exiting the breaker, and there is not a broken connection between the breaker and the unit. That problem will need to be addressed as appropriate, by replacing the breaker or pulling new wires through the conduit to the unit.

If there is power supplying the timer, use a short piece of wire to the coin switch terminals of the timer to provide the required number of coin pulses. If motors start you have a bad or improperly connected acceptor. Replace coin acceptor.

If motors don’t start after the correct number of coin pulses, use a voltage meter to determine if there is power exiting the timer.

If there is power and the motors don’t start then you have:

  1. Bad motors;
  2. A bad connection to the motors;
  3. Or in some units a bad relay.

You will have to check for power at the motors or relay to make sure there is not a bad wire from the timer to the motors or relay.

If a relay is used, check the power entering the relay and exiting the relay. If it enters but doesn’t exit, replace relay.

Check for power at the motor(s). As strange as it seems I have found all motors go bad at the same time. I can only guess one failed and the other shortly thereafter.

Following the above procedures should help you cure the cause of any problems as efficiently as possible.


Earl Weiss is the owner of four carwash locations in the Chicago area.

Professional Carwashing & Detailing recommends you first contact your supplier or manufacturer before developing a troubleshooting, repair or maintenance program to learn their recommendations and suggested processes.