Car Wash Forum
This is a sample guest message. Register a free account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members through your own private inbox!
D & S vacuum
- Thread starter aca carwash 2
- Start date
MEP001
Well-known member
I see you have a volt meter out in your picture. It's an easy chain to check for power. Check for voltage to the transformer, then voltage from the transformer to the timer, check for timed load from the timer when you start it, then check for power at the mercury relay, both power in and out. At some point you'll not have power where you should and you'll know what's wrong.
aca carwash 2
Member
Thanks MEP,
Is the mercury relay the part on the top left ? Whats its part in the chain of command. I think I have 124 volts to the timer, but won’t start?
Is the mercury relay the part on the top left ? Whats its part in the chain of command. I think I have 124 volts to the timer, but won’t start?
Fatboy769
Living the American Dream
Yes, it is the part on top left. When it receives power from the timer, it transfers the hot side of your 120V from the second terminal down from the top of it, to the top terminal. Those 2 wires are the hot side going to each motor. In your pic, you can see at the bottom of the mercury relay that the coil voltage is 24V, when the timer is energized, you should have 24VAC between the black and white wires one the bottom of the mercury relay. There should not be 120VAC to the timer, what ever voltage you have going in the timer, is what you will have coming out of it, on the load side. That voltage should be 24VAC, since your coil voltage on the relay is 24VAC
aca carwash 2
Member
If the vac timer doesn’t energize can it be mercury relay? How do I check the mercury relay if the timer doesn’t energize ? 
Fatboy769
Living the American Dream
If the vac timer doesn’t energize can it be mercury relay? How do I check the mercury relay if the timer doesn’t energize ?
What kind of timer do you have? Do you have a picture of your timer? I sent you a private message this morning
MEP001
Well-known member
The vac timer needs to output voltage to energize the mercury relay. You'll have to check for voltage out from timer. Go back to the chain of voltage checks I listed earlier. Your logic of "If the vac timer doesn’t energize can it be mercury relay?" is like wondering if a light bulb is burned out because it's not working during a power failure. Check the chain of power and you'll find a failure somewhere.
aca carwash 2
Member
Ok, based on this information I went back yesterday and worked on this vac. The mercury switch had 2 volts going to it. When I activated the timer (the vac didn’t come on) I now had 24 volts to the mercury switch, like the other vac I checked that was working. I then checked the voltage to the motor and had nothing. On the other vac I was comparing it to it had 120 volts. So I have assumed it’s the mercury switch, normally open and ordered on yesterday. Does that sound correct? One thing I did notice yesterday when fixing it with this information is the ground wire on this vac came lose and was touching the lead wire to the motor. Could this of shorted the mercury switch? It looks like it took a good piece off of the end of the wire.
Fatboy769
Living the American Dream
Sounds like there is an issue with the mercury relay. Only other thing I would have checked, would be voltage between the second terminal down from the top of the mercury relay to ground with the timer not activated. Should be 120v, that is what is transferred to the top terminal when the mercury relay is activated, which goes to your vac motors. I would think that if you had a ground wire touching the hot lead going to a vac motor, as soon as the relay engaged, it should have tripped your main breaker in the electrical panel due to a dead short. I can't see how that would damage the mercury relay. I know you said earlier in this thread, that you thought you had 124V to the timer you replaced, if for some reason you did and you activated the timer, that would damage the mercury relay.
I’m going to have to go with Fatboy on this one. It’s a pretty simple control system. If you have 24 volt power coming out of the timer and 24 volts at the mercury relay solenoid and 110 volts at the lower top terminal, but no power on the top terminal your problem is with the relay.
Be sure to order the right voltage mercury relay. I have a changer customer who had a 24 volt mercury relay go bad. He replaced it with a 110 volt relay and it wouldn’t start, he replaced the timer, still wouldn’t start, he replaced the coin acceptor and it still wouldn’t start. He called me and told me what the problem was and told me what he’s done. I sent him my spare 24 volt mercury relay and it works. 24 volts isn’t enough power to pull in a 110 volt coil.
Be sure to order the right voltage mercury relay. I have a changer customer who had a 24 volt mercury relay go bad. He replaced it with a 110 volt relay and it wouldn’t start, he replaced the timer, still wouldn’t start, he replaced the coin acceptor and it still wouldn’t start. He called me and told me what the problem was and told me what he’s done. I sent him my spare 24 volt mercury relay and it works. 24 volts isn’t enough power to pull in a 110 volt coil.
aca carwash 2
Member
I replaced the mercury switch today and it fired up first try. Thanks for all your help.
