This is a continuation of a brief thread I started back in January, dealing with the issue of my Pavoni PUB 1V overfilling while espresso is being extracted. I removed the FloJet and let the machine's Procon pump draw water directly from a 5 gal bottle, and that made things much better, and I've settled for using it that way for the past six months or so, but it's time to try to fix it.

To clarify, the pump and sensor work fine when I draw water from the hot water valve, filling the boiler just over half-way when the level drops below that. But when I want espresso, the pump runs while it is pulling the shot and fills the boiler to excess. The consensus now seems to be that there is a crack in my heat exchanger.

I removed the fill valve to make sure it was connected correctly and free of debris, and I've double checked the fill sensor, and all that looks good. What I need help with now is how to check the HX. On this model, it cannot be removed, but is integral to the boiler, so if the HX is bad, so is the boiler. And according to La Pavoni importer, that boiler is no longer available.

Please tell me if my logic is correct: If the HX is good, then I should be able to empty the boiler but the HX remain full of water. But, if the HX is cracked, then it will leak into the boiler and empty along with the boiler. Am I missing something about how HX's operate? What else can I do to check the HX?

Thanks for any advice you can shoot my way.

The other thing it could be is:

When you activate the pump to extract espresso the following occurs
1. pump turns on
2. solenoid to group opens (to allow flow)
3. solenoid for filling boiler also opens (incorrect wiring connection?)

The above scenario is a possibility, as I have first hand experience of such a thing.

To check that this is not the case, disconnect the fill solenoid only. Then run a shot as per normal and check to see what happens to the boiler level.

Otherwise, a split in the HX is a possibility

To check for split in HX:

Drain boiler
Disconnect element
Disconnect autofill solenoid

Then run shot through group as per normal. If you have a split in HX, then boiler will fill with water.

Well, I ran both tests, and the boiler keeps filling even though I disconnected the fill solenoid. The strange thing is, I couldn't keep the boiler empty because the the pump kept filling it up, even with the fill solenoid disconnected. So I disconnected the fill sensor, but that didn't make any difference. After I emptied the boiler, as soon as I turned on the machine, the pump immediately filled it up. After it stopped, I ran a shot, and the boiler filled up some more. I would conclude then that the HX is cracked, but why does the boiler fill up with the fill solenoid disconnected? Do I need to have the wiring looked at?

Back to my first question: Can I empty the boiler and then look into the HX and see if it is empty too, which would indicate the the HX is cracked?

If the crack is located up high, then the hx will not completely drain. Your logic is good on that line of thinking however.

Disconnecting the fill solenoid and the boiler still filling up, could be that you have some debris keeping the valve open. If you had the machine plumbed in, the other thing that would happen with this scenario is that the boiler will fill overnight by itself since the water is pressurised. The debris is keeping the seat of the solenoid ever so slightly open.

Have you disconnected the heating element as previously advised? Can you post some pics of the appropriate machine internals? Simply disconnecting the level probe causes the fill solenoid to open (if it is electrically connected) and the pump to run. This is how the boiler fill control system works.

But when you electrically disconnect the solenoid, that takes it "out of the picture" unless it is mechanically faulty. The fill solenoid valve should have numbers embossed on the inlet and outlet ports. "1" is the inlet from the pump and "2" is the outlet to the boiler.

Disconnect the tubing line from the fill solenoid to the boiler at the boiler end. Electrically disconnect the fill solenoid. Plug the boiler port with a simple rubber cork. Attach some clear flexible tubing to the line.

Run the pump with a blank filter installed. If there is flow from the clear tubing, the solenoid valve is mechanically faulty or installed backwards. If the boiler is filling, the hx has a crack. This is all easier said than done but you want to make sure you know the source of the problem.

I have to leave shortly for a three day trip, but I'll apply your further tests when I get back. I did notice just now however, that the body of the fill valve is uniform, and can be installed either way. I didn't consider that it could be reversed because it looked like it could only fit one way, but now I see that I hadn't considered the connectors could have been mounted wrong by the previous owner. So I'll start with that, then proceed with the other tests if that doesn't fix anything and post results with pictures. And yes, I always disconnect the heating element when working on my machines, unless of course I need the heat.

Thanks for helping out.

Well, I dismantled the fill valve/solenoid, and sure enough, it had been assembled wrong by the previous owner. Although it has caused me a lot of headache, and some embarrassment for not seeing this sooner, I can see why I got the machine for such a good price! Everything is flowing now the way it should, and the machine is back in business. Many thanks for all your help!