How to Fix Heating Pump, Vaillant F75 Faulty Pump, Replaced the Capacitor in the Pump and its Fixed

[@RockinRedRover]

Many thanks Mark for this very helpful video - I'm a DIYing mech engineer albeit with no prior experience of combi boilers. Boiler had gone u/s, ironically after cleansing the system ? (moved sludge maybe), so had to redrain down the system again and then the boiler too (my first time), all relying wholy on researching YT vids esp yours !. Despite initially thinking (hoping) was just a dirty pressure sensor, I then got the impression the pump was dead, BUT visually was fine and impeller shaft rotated freely. Belatedly after seeing this video I opened the lid and the capacitor had exploded ! - no idea why, hopefully "just" old age as it runs hot and its probably over 10 years old. Anyhow managed to find a local shop with a second hand one out of a different brand pump, but still same size and impedance (2.5 microfarad, seems standard), and now all is running again and we have hot water in taps and rads for first time after 4 very cold and grubby days. Fingers crossed it will stay so. As part of the "service" I also cleaned the pressure sensor and AAV, and touch wood rads are hotter than ever now. Thanks to you Mark and your fellow engineers on YT.

[@InvictaBuilding]

Very helpful video enjoy your detailed information regarding appliance issues

[@miqul76]

Thanks a lot! You saved my pump and money :)

[@macpatel7810]

Nice job. We'll explained

[@committoget]

I am one of your subscribers who keeps watching your videos regularly. I had F75 error with red light on in my Vaillant Ecotec Pro 24 (old type). I called a local Boiler Engineer who replaced the water pressure sensor. Red light and code F75 gone, hot water started coming but there was no central heating. I called the same guy and this time he took the 22ml black rubber pipe from the copper pipe which is coming to the water pressure sensor socket and he put it back with the jublee clips after cleaning the badly clogged pipe. However, hie did not take out and clean the similar black rubber pipe which was on the other side above the pump, Anyway, fault F75 came again even after replacing the water pressure sensor and boiler pressure is not going above 0.8 Bar after resetting. That guy left the job and did not turn up. When he was cleaning the black rubber pipe and replacing water pressure sensor somehow he left unconnected two small white connectors of purple and black wires and black connectors of yellow and black wires which were fixed on a little rectangular copper strip that I guess supposed to go somewhere on or around the hear exchanger plate but I cannot see any place or any sign on heat exchanger plate where this slipped on copper plate with two black connectors should go. Probably these unconnected connectors are causing the error F75 and water pressure is not going up. If you give me any clue where these connectors will go and what I suppose to do to run my boiler it will be very kind of you. This is an old ecotec pro 24. I appreciate your reply. Many thanks David.

[@carlsimpson4875]

Good video well explained, I have a lazy capacitor on solar system pump it works for four or five days but then it gives in and I have to manually get the pump running by tweaking the speed switch on the pump. I’m going to replace the capacitor and see if it solves the issue.

[@waheedali1674]

Good helpful video please share parts link is well in future videos Many Thanks in advance

[@ShafaqIftikhar-pw9ld]

Great a video!!!!

[@louiepage6623]

Hi can u used 1 of theys pumps to move water ..not installed on a boiler

[@mustafanaser9789]

What does it mean if water consistently comes out of the hole after the screw is taken off? Water don't stop flowing

[@sirajesakjee5092]

Great video. Can you advise which capacitors are common. I might start to keep these in the van as stock.

[@andrewashburner]

Hi, do i need to drain the system pressure before removing the pump screw?

[@whatsmining9917]

You can turn off the radiator feed & return taps at the boiler then drain using the red pressure release valve so you only have to drain the boiler

[@noslrak2000]

Cool stuff, what would you say about the pump that has hiccups? What do I mean by that? Well, the pump is running but one once every few moments it that sound that comes of it changes the pitch. 4 years ago the other pump died by becoming too noisy to sleep at night. So, it is only capacitors that fail. Why do they change sound???

[@RockinRedRover]

maybe knackered bearings within the pump ? - how old is your pump ?. Does it run hot, can you touch the pump's surface when it's running, not only does the motor generate some heat, so it can absorb heat from the hot water it's pumping, ideally the pump should be on the return side of the circuit so its pumping cooler not heated water. Bearings do NOT like high temperatures as their lubricating grease drys up. Plus the pump's internal seals can fail, so allowing the water into the bearings, also very bad for their happiness. Also worth bleeding the pump, loosen the screw-in plug in centre slightly to let any air out, but beware hot water will follow, use a cloth. If lots of air in system then can cause cavitation, where the pumps alternately pumping water and then air, hence changing the noise it makes.

[@noslrak2000]

@@RockinRedRover Thank you for your comeback on my earlier comment. I've tracked it to boiler's PCB. Looks that it was cycling the pump between high and normal RMPs. Changed the PCB and that issue is no more. Hopefully another 13 years of running ahead (Or at least without PCB issues)...

[@RockinRedRover]

@@noslrak2000 welldone sir, hope the PCB wasnt too pricey, maybe 15? years ago I fixed our Gloworm boiler with a second hand pcb costing a fiver iirc. (and btw, even tho I'm biased as am a mechanical engineer, I'm not surprised its the electronics that have let things down, yet again... ;). - indeed, using these vids I've jsut serviced and fixed our Vaillant boiler of similar age to yours (different house than before), turned out the start capacitor inside the pump housing had exploded, age and heat fatigue I guess, replaced with another 2nd hand one for a fiver again lol.

[@noslrak2000]

@@RockinRedRover No, £54 BNIB but off Ebay. Screwfix has it too but for a touch under £300. Hopefully it will last another 13 years. For £54 well worth the price!

[@RockinRedRover]

@@noslrak2000 too right, you wouldnt have been able to get a heating engineer to enter your house for just £54, nevermind do anything else ;-) !

[@LewMeredith]

How do you test a capacitor?

[@jamesasprey2092]

Esr meter is the best option. Multimeter can also test if it has that function.

[@whatsmining9917]

You can spray in some wd40 or silicone spray

[@geoffaries]

Interesting, but 10 minutes too long. I would suggest that you discharge a capacitor before removing it as it could give you an electic shock. Then I would test it with a multimeter which has the capacitors test function, to ensure that its faulty, nowadays it's rare for a pump capacitor to fail. You probably wont be able to get the correct capacitor locally, so it will be mail order, so potentially no heating for 3 days only to find out that the pump is faulty. I would recommend the use of a screwdriver with a much wider blade and rugs under the pump to collect the water.

[@RockinRedRover]

Hi, my pump's just stopped working, rotates freely but nothing happens when powered-up. I find the capacitor has exploded, was this a cap failure OR did it explode due to another failure within the pump ? Chicken or egg. Thanks. (PS a week later and pump still running perfectly).

[@CaliforniaLloydUK]

F75 IS A PRESSURE SENSOR not a pump

[@pizzamad3334]

But if the sensor doesn't register a pressure change because the pump not working....

[@amoksedas1676]

Man u saved me a lot of headache and money, thank you very much.. My pump was stucking. After turning few rounds my boiler just works like a charm again🫶

[@madmaycon2531]

Amazing video !!!!!