Central Vacuum pulses

I have an AirVac Gold series, model #ZX6000, that has decided just to pulse rather than run when any remote outlets are used. The pulsing is on / off at about 2-second intervals. It works just fine with the tank switch. The pulsing occurs at all of the remote outlets. Any solutions or suggestions on where to start analyzing?

 

The switches are all open circuit and all connected in parallel.
There should be two terminals right on the unit.... try shorting them with a screwdriver.
Does it run ok there ?

 

When I short across the two control wires at the tank, the unit does not come on. I am not certain I am making good contact though as when I remove the control wires and jumper across the two tank terminals the unit comes on and runs fine. If I install the two control wires to the tank and go to a remote outlet and jumper across the two terminals there, the unit pulses.

 

Ok... good. So that's telling you that the vacuum itself is ok and the problem is strictly external.

With that being said you have a confusing problem. Most central vac hose connection ports create a short when the hose in inserted. You've tried a short and get the system pulsing. On the surface that says the wiring is too small/thin. That would be very rare as the unit has an internal transformer and the remote is forming a basic low voltage switch. The amount of current should be minimal.

Can you post the model number off the vacuum ?

 

The unit is an AirVac Gold series, model number ZX6000

 

That's a standard AirVac open circuit connection. As I explained before.... a short anywhere on those two wires should make the vacuum run and stay running. The specs call for #18 wiring. I've seen smaller used and work.

Do you have the wall connection plates with the 120v for powered tools ?

The wall plate is held in with two screws. It can be removed without harming the vacuum pipe in the wall. The plate was designed to be changed. I would pull it out and try shorting the low voltage wires there.

This is a rare problem as the system is so basic.
Nortek AV-ZX installation - pdf

 

The wires appear to be 18 guage and the outside sheathing says "Type CL2". There are 3 conductors, white, red, and black. The red goes to the green indicator light that flashes when it is time to change the filter. It is getting power as it is a constant green.
I have opened the wall plate and jumpered across the two conductors at the screws and that is when the system pulses. I opened another wall plate and it reacted the same way when I jumped across the same screws.
You mentioned a transformer inside the unit. Could it have developed a problem? The unit is about 23 years old.

 

The CL2 makes is type accepted for in wall low voltage wiring.

I'm at a loss. I've never seen a system with the filter light on the plate and I've worked on many.
I can't find a control board that supports the filter light.
There are basically two boards. One has the transformer on it and the other has a separate transformer.

Can you shoot and post a few pics of the system for me. The top of the motor should come off and you can see into the unit there.... How to insert pictures.

 

The way my system is mounted, the motor cover is on the bottom. Here are a few pictures of its workings. It does look to be rather simple, but I guess the real system is on the little board. It does have the transformer on it. I included a picture of the outside of the tank where the control wires plug in. The button is a fuse and the little light is the one that is on solid green all the time, but it begins to flash green to indicate the filter needs changing. This same green light is on all the wall outlets and will flash green there at the same time.
Incidentally, I decided to check the voltage across the two screws on the wall outlets. When I touch a voltmeter to them, the unit came on and still pulsed. But the interesting thing is that when I removed the voltmeter leads, the unit continued to run. I had to unplug it to turn it off.

 

Good pictures

That is a M-CB15A control board. Very basic. No logic. Transformer and relay. A typical two wire system that's found in most central vacs.

We need to clear up some previous discussed issues.

You said there was a three wire connection from the vacuum to the plates. I don't see a three wire connection at the vac. I see a red and white wire connected. At the plates you have three wires ?
You said the red wire goes to the LED. That would not be correct. A direct short is required on red and white. The LED in the red line would be a problem.

I have a feeling that you have plates there that do not not belong to that system. You need the red and white wires to be on the switched contacts. So far.... I haven't seen anything that would require the third/black wire.

 

You are correct in that there is only a red and white conductor. However, the red is connected to the green light that I mentioned and there is a black jumper from there back to the other side of the switch. The green light is only on if the hose is in place and shorts across the two wires. The green light is on continuously at the tank. Here is a picture of a wall outlet. I opened another wall plate and it is wired the same way.

 

Disconnect the LED.
Connect the red wire to where the black wire is currently connected.

The vac won't fire up with the LED in series.
I've never seen that type of plate and I'm not sure how the LED is electrically supposed to work.
I haven't been able locate that type of plate in any of my supply company catalogs.

 

Will I need to do the disconnect at all wall plates, or can I do it at only one as a test? The system has been in place for over 20 years and worked until a week or so ago.

 

I would try it at one plate as a test.

I've never worked on a vac system that had the LED in the plate. I'm trying to find more info. If you see a model number on the plate.... post it. Maybe post a picture of the LED area.

With most vacs the transformer and the control relay are both AC. The LED inline would send DC to the relay. That would keep the relay from getting a true 24vac. The Electrolux system uses DC switching and those plates would work there.

 

I rewired one wall outlet to take out the filter status light. When I jumpered the outlet, the vacuum came on and ran fine. When I removed the jumper, it stopped. I then rewired the other 3 wall outlets downstairs and decided to test the system with the vacuum hose and carpet head. It worked just fine. When I turned the switch on the head off, the system turned off. But when I removed the hose from the wall outlet the system turned back on and began pulsing. Maybe I have to complete the rewiring of all wall outlets for the system to work.
Here are some pictures of the wall outlet plates. The brand appears to be Electravalve.

 

Pete,

Thank you so much for your patience and help. I know it took me a long time, but I finally finished rewiring all of the wall outlets to remove the led bulbs and wiring. Low and behold, the system seems to work normally.

Thank you again!
James

 

I had emailed a fellow installer to see if he was familiar with that system.
I hadn't received a reply yet.

I'll keep looking into it. Glad it's working normally again.