Baxi 105E Instant ch no hw

[jd_hants]

ch is fine.

Needle on differential valve does not move when hot water flows - no matter what flow rate. Checked diaphragm - looked ok but replaced anyway. Needle moves ok and doesnt seem to stick. Checked the two sensing pipes - clear.

When microswitch triggered manually then divertor operates, boiler fires up and heats water as normal so PCB seems ok.

have already replaced HE as hw took ages to heat up / start to run cooler when flow increased.

any ideas???

 

[baxpoti]

The pin (needle) comes out about 10mm more when on demand, so about 20mm total.

Does yours come out this far?



Long shot......

Hot and cold reversed?

 

[jd_hants]

Hi

Hot and cold right way round. Needle is about 10mm out. Doesnt move at all when hw tap opened. If pulled with pliers it will come out the extra 10(ish)mm and operate the valve. Otherwise nothing. Wondered if it could be the valve itself?

 

[baxpoti]

Part No. 248734

 

[doyle]

done exact same job after a service water end of divertor valve..diaphram kit can be bought but the needle tends to s4ize so its easier to just change entire water end cost £62 approx depending where you buy the part.


try turning on bath tap full, if hot water prevails then im right could also see if you get hot water if central heating is on, another indicator to the fault on baxi 105 e

 

[jd_hants]

Turning on the bath full has no effect. Just stripped it down again - cant find anything - thought maybe some bits of debris might be stuck in the sensing pipes or filters but everything clear. ch works absolutely fine. hw works fine when microswitch operated.

should the needle of the hw differential switch move when hot water flowing even if not inserted into the valve??? just trying to narrow down problem. think it must be either the valve - i.e. weak spring or something or the diff switch - although had both apart and things look fine.

completely baffled

 

[ChrisR]

Is the gland in the front end of the diverter section seized?

In the mauve bit.

Also check the front red bit

 

[Rob]

Best thing to buy is the HW diaphragm repair kits. which includes diaphragm, gland nut and push rod. No need to buy the brass housing.

 

[ChrisR]

Sure but you can't buy just the part in the last pic above...

 

[Rob]

Sure but you can't buy just the part in the last pic above...

Why would you want to? Isnt it the flow switch faulty rather than DV?

 

[ChrisR]

I'm not sure that the spring in the diverter section doesn't help push the spindle which operates the flow switch. Are you Rob?

If it IS , and the gland was sticking, it could be causing the problem the OP has. Too lazy to get one out to check!

If the DV section does nowt, the boiler should come on as long as the red gland and diaphragm are ok.


This doesn't stack up though:

When microswitch triggered manually then divertor operates, boiler fires up and heats water as normal

Operating the microswitch doesn't move the diverter...

 

[Vic Spanner]

Guys posting above the OP is talking about the instant not the E version..

Sounds like new Pressure diff required

 

[namsag]

Chris that is a picture of the 105e the topic is the 105e instant which has a different set up

 

[doyle]

save yourself the hassel, buy the front end and change it.


the needle should move out towars the microswitch every time the tap is turned on, as ive said these can seize, it cost 62 quid for the front section.

it isnt the micro switch, you can test that by operating the switch where the needle makes contact if needle aint moving its the hw divertor, which also has a diaphram inside.

ref to images.

turn off water inlet and drain boiler, remove the micros switch, undo pipes undo the two screws at rear and bobs your uncle blue section comes out and fit in reverse order pushing part hard into the ch divertor

 

[doyle]

just read its instant,

on this one change entire divertor valve, yours is still seized cost around 80 quid + for that one. have done one of these also and pushrods are likely to seize with ware and tare
note hw divertor does seperate from the manifold at rear end