Vibratory pump in-line resistor?

#1: Post by **Shuka** » September 29th, 2022, 11:30 am

Folks -
While trying to reduce pump noise in my "new" Andreja Premium, a component in-line with the pump wiring (photo) shorted to the case (interestingly fusing the pump switch at the group closed). I've measured its resistance - it now looks like a DC-short. Does anyone know what it is or what it's purpose is? A guess from an electronics nerd was that it was a positive-coefficient resistor to temper the vigor that the pump starts with. The writing is: "F11Z" and on the back "F11" with a logo that appears to read "MIO".
Thanks,
Shuka

#2: Post by **cafeIKE** » September 29th, 2022, 11:43 am

Photo missing.

It's likely a thermistor to reduce the voltage to the pump if it gets too hot. It should measure nearly 0Ω when cool.

#3: Post by **Nunas** » September 29th, 2022, 11:47 am

Some machines, but far from all, with vibe pumps have a device in series with the pump. It's a thermostat (thermistor). If the pump gets hot, the devices shuts it down to save the diode or coil from self-destructing. If your device is mounted right up alongside the pump, then this is likely what it is. Vibe pumps have a duty cycle, often in the order of 50/50 on/off, and a max running time of 60 seconds. You can look your pump up on the ULKA site and see the parameters. This should not be confused with some other vibe pumps that have an external diode (the ULKA pumps have an inbuilt one). If your device tests as a short in both directions, then it's a thermostat. If it tests as a short in one direction and an open in the other (or nearly so), then it's an external diode.
Edit: I originally said external resistor...a senior moment. I meant external diode, which is what I said in the subsequent post. Getting old sucks

September 29th, 2022, 11:51 am

Boom - asked and answered. Thanks folks. I'll tuck that in with the pump (hadn't realized it shouldn't be loose).
Cheers-
S

#5: Post by **Nunas** » September 29th, 2022, 11:53 am

If it's a thermostat/thermistor, it has to be tucked in tight. If it's a diode, it should be kept in the open.

September 29th, 2022, 12:13 pm

It's a Klixon F11 microtherm for overheating protection. It goes in the slot as in the pic CafeIKE posted.

#7: Post by **WWWired** » September 30th, 2022, 2:41 am

Fantastic info by cafeIKE, Nunas and balheadracing!

A bit of extra info can be found also at HB site-sponsor Stefano's Espresso Care

I read somewhere that if a pump begins to overheat regularly causing the thermal cut-off component (similar to the one pictured above) to open the electrical circuit and shut the pump down (due to coil deterioration or faults developing), that while a new one is being ordered in, some folks might pull the thermal cut-off from its pocket on the pump coil housing to prevent the thermal cut-off from being exposed to the pump heat and to keep the pump circuit from from begin opened at the thermal cut-off component (just a very temporary measure).

#8: Post by **Jeff** » September 30th, 2022, 1:18 pm

If your pump is overheating, fix the problem. If you're lucky, all you'll do is melt the coil insulation and have it pour over the inside of your machine. If you're less lucky, short circuits and resulting fires are a distinct possibility.

(If you're trying to pull two-minute extractions or the like, buy a machine with a rotary pump. The typical Ulka pumps are only "good" for a minute or so, and that's with 20°C water in a 25°C environment. Neither of those conditions are met in most home espresso machines.

#9: Post by **cafeIKE** » October 1st, 2022, 1:23 pm

Jeff wrote:The typical Ulka pumps are only "good" for a minute or so, and that's with 20°C water in a 25°C environment. Neither of those conditions are met in most home espresso machines.

That being said, I've never had one fail in 30+ machine years. Back to back shots in a 4 shot series don't raise the temperature in the thermistor well enough to make any difference. Ditto running for a couple of minutes during descaling.

In my 2006 e61 Vibiemme HX, I added insulation between the pump and the boiler. Only replaced before I sold the machine in 2021.

Replaced w heavier duty model in 2008 Vibiemme DB in 2020. Original pump was still working fine

#10: Post by **Jeff** » October 1st, 2022, 1:35 pm

Not everyone has the same luck with Ulka-style pumps' longevity.

Here is someone else's, which pretty clearly is suffering