Ulka EFX5 Stalls

Equipment doesn't work? Troubleshooting? If you're handy, members can help.

#1: Post by A99x1 »

I have a Bezzera Magica and after 10 years of service the EX5 pump died. I replaced the EX5 with an EFX5. The new pump works fine with the exception that once I pull a shot I have to wait several minutes before it will work again. My typical shots are 20-30 seconds. If I try to flush the machine immediately after the shot, the pump just hums. No water is pumped. A few minutes later it works fine. I never had this issue with my EX5. Is my EFX5 defective? Any advice is appeciated.

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#2: Post by civ »


Welcome to HB. 8^D!
A99x1 wrote: ... Bezzera Magica ...
EX5 pump died.
... once I pull a shot ...
... several minutes before it will work again.
Any advice is appeciated.
Please do take a look at these links:

/search-res ... 1089664j16

As you can see there are a great many entries but that only reflects the incredible breadth of the data stored in posts at HB.

See this one also: Difference between Ulka EX5 and EFX5 pumps



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#3: Post by cafeIKE »

Short answer is likely the thermistor is overheating due to a change in pump orientation - or the pump itself is faulty causing the thermistor to function.

You can test the thermistor by measuring cold resistance and immediately after pulling a shot. With the machine unplugged, measure across the two thermistor leads. It should read less than 1Ω on a cold machine and only a few Ω after several back to back shots.

The thermistor should be fully inserted in the pump with the metal side facing toward the pump body.

Many Bezzera machines have the pump poorly oriented.
It very close to the boiler and the thermisitor faces the boiler.

Any change in the boiler / ambient / location that could cause a temperature increase?

A99x1 (original poster)

#4: Post by A99x1 (original poster) »

Thank you for the replies. I will check out the links and test the resistance on the thermistor. Here is a photo showing the proximity of the pump to the boiler on the Magica. Would that be considered to be close?

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#5: Post by cafeIKE »

Looks like it should be OK.

If the wires are long enough and there is enough clearance for the connectors, I'd rotate the pump body so the connectors are on top. The body will rotate around the outlet if the out is held with a wrench [or pliers] on the flats.

Make sure the wires have a drip loop so water cannot run into the connectors.

How hot does the pump body get after a shot?
How hot does the thermistor feel after a shot?

There is a possibility the control box is having an issue with the higher wattage pump. Where is it located and how is it oriented?

A99x1 (original poster)

#6: Post by A99x1 (original poster) »

Great point. I did not consider the wattage difference when I ordered the EFX5. That could be the issue. I've ordered a new EX5 pump just to be sure.