Intermittent loss of pressure

[Legacycarwash]

Good afternoon everyone.
still learning so don’t tear me up too much.
4 bay self serve wash. 310 cat pumps. Have a bay that sometimes when it’s switched to rinse the pump turns on but only city pressure. Turn it back to brush and back to rinse it works fine. When it doesn’t have pressure everything seems okay. Pumps turning. No noise. City pressure is running thru. Just no pressure. I just can’t get it in my head why it’s intermittent. It’s not electrical, that would explain it. But how can pressure be intermittent? Then just turn the knob back to brush then back to rinse and it’s perfect?? What the heck

that’s for any tips!

 

[MEP001]

If it's only on rinse, it's one of two things. Next time it happens, look at the contactor while it's on but no pressure. If it's buzzing, try to push it in. If it goes in and stays, you have too much current draw for the low voltage wiring. If it's not buzzing and you can press in the contactor and it doesn't lock in, the rotary switch is failing.

 

[Legacycarwash]

If it's only on rinse, it's one of two things. Next time it happens, look at the contactor while it's on but no pressure. If it's buzzing, try to push it in. If it goes in and stays, you have too much current draw for the low voltage wiring. If it's not buzzing and you can press in the contactor and it doesn't lock in, the rotary switch is failing.

So when it’s happening the pump is spinning. Motor sounds normal. No abnormal buzzing. That’s what’s weird. Everything seems normal just no pressure.

 

[MEP001]

Can you post some pictures of the pump and plumbing?

 

[Legacycarwash]

 

[MEP001]

Might still be the rotary switch. Test the rinse solenoid with a screwdriver, you should feel a magnetic pull when you hold it just above the coil. If you have this failure again, check the coil with a screwdriver (You can also use a voltmeter to check for power, the screwdriver is faster). The rotary switch can do this when it starts to fail.

 

[Legacycarwash]

Might still be the rotary switch. Test the rinse solenoid with a screwdriver, you should feel a magnetic pull when you hold it just above the coil. If you have this failure again, check the coil with a screwdriver (You can also use a voltmeter to check for power, the screwdriver is faster). The rotary switch can do this when it starts to fail.

Okay. I k ow I’m being a pest here. But if the switch is failing the motor wouldn’t turn on correct? That’s why I’m getting confused. It’s spinning yet no pressure.

 

[Randy]

My wild ass guess from looking at the pictures you’ve got a bad PR-1000A Zero Pressure Regulator. I’ve seen a few of those act like what you’re describing. But normally when they go bad, they go bad, they don’t work intermittently. Open it up and take a look inside, I'll bet the pot metal plunger is cracked or broken.

 

[MEP001]

Whenever I've had a PR-1000A fail it doesn't regulate the water pressure, it just sends it straight through and the pump doesn't draw soap or wax anymore. It won't affect the pressure.

The switch could be failing and not opening the rinse solenoid. There are typically two outputs, one for just the motor and one for the solenoids. That's why I recommended you check the solenoid for the cold water. I'm pretty certain that's the only thing that can cause your problem.

 

[Legacycarwash]

Sorry for the late response, took a while to find time. But Randy you nailed it. replaced the zero pressure regulator and everything went back to normal. Still seems weird but whatever.
Thanks for your help guys!