Oven Repair I

Moving along, the next item suffering is the oven. There are two faults, a broken button on the control panel and a failed seal on the top oven/grill. The oven is a Zanussi ZGC551GXC gas oven.

I started with the seal, just because this should be the easiest one to sort, in access terms at the very least.

Broken top oven door gasket

Removing the damaged seal was not a problem, it was held on with 4 hooks at each corner. So the whole thing just pulled out easily. The next part of the job was to get a bucket of hot soapy water and start cleaning both the stuff as it came off the oven and the exposed areas left behind.

Rear view of removed gasket 

You can see from the picture that the top portion of the seal has had more heat damage than the bottom which why it has parted there.

A quick trip to the Zanussi support pages yielded no information. Not even a link to their on-line parts shop where all the part diagrams, part numbers and prices are! So a replacement seal would have been £21 plus £2 p&p and another £8 for a replacement timer button, or £31 for the pair. The seal is only mildly expensive compared to button which costs its weight in 9 carat gold. Time to make do and mend I think...

Cross-section of door gasket

On inspection I found that gasket was originally sealed by inserting a joining piece into a void running the length of the gasket. It seemed that I could just replicate this. As I wasn't sure how hot the gasket would get in operation I plumped for a piece of thick aluminium foil folder over.

Foil from top of coffee can

Folded across a wire to make require profile

Using this and a piece of wire to form the spike in the profile I made a 4 inch piece to join the ends.

Home-made joining segment

As you can see from the photo, this was only partially successful as the perished rubber had a tendency to part. When I refitted the gasket to the door the aluminium kept slipping out of the rubber so to prevent this and deal with the perishing I reinforced it with four staples underneath the flap of the gasket.



Repair reinforced with staples

This worked and the whole thing went back into place with no problems.

Repaired and refitted top oven gasket

The less damaged part of the seal is now at the top of the oven aperture and hopefully we'll get a further 4 years of service out of it before it needs properly replaced. On to the snapped button!

Time spent : Day split over an afternoon and morning
Cost : £0.00

Dishwasher cleaning products

Yes, I have got the bit between my teeth regarding maintenance of the dishwasher. As I noted the water matrix looked a bit gunky but impossible to clean manually. What to do? Use a dishwasher cleaner I guess.

Based on a Google search for dishwasher cleaning products, the three most commonly mentioned are Finish, Bosch and Dr Beckmann. But what's in them, what do they do, and are they really required anyway?

Let's start with Finish which has been available in two formats.

New Finish

Old Finish

The older one appears to mostly be citric acid (15-30%) and a non-foaming detergent (5-10%). Why non-foaming? Because this is what happens if it isn't. While the newer one is exactly the same thing but with a splash of EDTA and bit of glycol ether (presumably to help form the upper blue phase and assist the detergent's effect). So in both cases it appears to be a bit of acid/chelator to descale and break down any fatty deposits and a non-foaming detergent to help shift any stubborn stuff.

As it's a powder, Dr Beckmann's has a different set of active ingredients being mostly sodium percarbonate (20-25%) and some coyly named oxygen-based bleaching agents (15-30%) which are probably also peroxide derivatives or activators for the percarbonate (I wouldn't be surprised to see EDTA in the mix again as well).

Dr Beckmann

Finally the Bosch dishwasher maintenance powder has a more comprehensive set of ingredients but the main constituents are citrate and percarbonate. There is also sodium silicate (an astringent), sodium carbonate (washing soda), longer chain detergents, EDTA, and a couple of industrial enzymes, amylase (a starch buster) and subtilisin (a protein buster).

Bosch maintenance powder

In summary the cleaners appear to be either citrate and/or percarbonate based plus/minus a non-foaming detergent. They are targeted at descaling, dissolving fatty deposits, and shifting stubborn residues that your regular dishwasher detergent isn't moving.

On the question of "Are they worth it?" there seems to be a lot of debate. The commercial cleaners generally recommend a monthly application. So, at anywhere between £2 to £6 per dose (or £25 to £75 a year) and given that a reasonable dishwasher will cost about £300 and should last ten years, if you are not using one of the commercial products and if (and it's a big if at that) this halves the lifespan of your machine you would have paid almost as much on even the cheapest cleaner as it would cost to replace your dishwasher every five years rather than ten. In that light they appear to not be very cost effective. More so as the bulk cost of the component chemicals is only a few pence.

The following comment from the Money Saving Expert forums gives an expert perspective,

"So do use the salt chamber and keep it full, buy rinse aid and add it and you will get nice clean stuff out every time, don't waste money on Calgon, dishwasher cleaner or tablets with added rinse aid or salt either because it's just a marketing con, I used to build and repair £20,000 commercial dishwashers so I know a thing or two about them."

Reading the thread a range of cheaper substitute options are suggested, vinegar, bleach, baking soda, washing soda, and bicarb. Of these vinegar seems the most commonly recommended, both as a cleaner and as a rinse aid (see here and here).

However there is some controversy about whether using vinegar (aka 5% acetic acid) will damage the seals and internal tubing of your dishwasher. A bit more digging shows that more seals are compatible with citric acid than with acetic acid, which may be one of the reasons why some of the cleaners are citric acid based. Whether this matters if vinegar is only being run in the machine a few times a year as a cleaner rather than routinely as a rinse aid I can't be sure.

Certainly some manufacturers specify that vinegar is safe to use in their machines, but the manual for ours didn't. The best way to establish if it is safe or not would be to contact the manufacturer, but with Neff that's another story...

In the meantime, the Finish bottles contain about 30-60g of citric acid which is easy to get hold of in food grade form. Five pounds will get you enough for twenty 50 g (=2 tbsp.) doses that can do the job of £80 worth of Finish cleaner. The loose crystals just be bunged into the powder compartment and run through a hot program. Percarbonate is also readily available but replacing the non-foaming detergent is a more awkward, but not impossible, proposition.

But if I'm just trying to replace a vinegar clean then a citric acid only swap seems most straightforward. I think I feel a trial coming on.