# Gaggia Classic: fixing the on-off light on the switch assembly



## phario (May 7, 2017)

I wanted to write a post here describing my experience with fixing the on-off light on a pre-2009 Gaggia Classic. Unlike components related in the main body like the pump and boiler, there is a lot less information out there on the switch assembly, and there is some general fear about disassembly of this mechanism. Here was the problem in my machine. The on-off light would almost randomly turn on or off. Most of the time, it would be non-functioning, but sometimes it would turn on, and might turn on with slight presses of the switch.

Here is a video of the error: https://streamable.com/l3i664

Based on this, some people suggested that it might be the actual physical switch within the assembly or the light itself.

Before you open the switch, there are two main references you can find on this:

[1] http://coffeegeek.com/forums/espresso/machinemods/641078: this reference is a text description of the disassembly; combine it with

[2] 



Basically, you want to follow the idea in [2]. I'll add a few points:



There are two metal clips that attach on the side of the assembly and clip into the main Gaggia body. You want to lift up the small tab with the hole while simultaneously pushing on the larger tab. Be careful because these clips are not particularly robust. 









The idea of [2] is that you can tape the centre section. This means that when you slide the rod out of the main assembly, the three buttons don't go flying. You can basically slide the rod out in one direction and operate on either the left or right switch.


** However, I would advise you to tape not only the centre section but tape also the other button that you don't intend to work on. Tape them tight. You do not want these switches to pop out because there are essentially springs in place holding them in. If the button is accidentally popped off and pushed back on at the wrong angle, the springs may be bent.


Once I managed to pop off the switch corresponding to the on-off light, I cleaned the various areas with a cotton swab. Apparently that was enough to get the light working again!









*Extra notes: *



Be careful about bending your springs. I managed to bend my coffee-on switch spring for the reasons indicated in ** above. That is, the switch popped off, and I tried to stuff it back in at a slight angle. I managed to get the spring bent back enough to not cause any harm. The spring dimensions are 15.9mm in length and 4.1mm in diameter.


I was afraid that I might need to replace the neon bulb and resistor. I believe that the resistor is 150 kOhms +- 5% (bands of brown, green, yellow, gold from left to right). I do not know where you should source the LED, but from reference [1] above someone recommended Lumex Part Number 1.7mA GT-NE4H1125. From [1] they indicate that the LED neon bulb is 11mm high and 4mm diameter.


Be careful rubbing electrical contact solution on the front buttons! Apparently that was enough to rub off the ancient white writing! Damn! Anybody have a suggestion for a white pen that can be used to fill it in?


*Question: *

I encountered something I don't understand. I wanted to test the LED. I placed the probes of a multimetre in diode testing mode at points A and B below and there was no current. When I place the probes at B and C, the multimetre beeped as it should. And yet the LED works. Why is this? The only thing I could think of was that the resister was 'screwing' this up and I would need to use a higher voltage input. But I would have thought that the resistor played no part if I hooked it up at point A to B.


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## Norvin (Sep 10, 2014)

Its a neon bulb, there will be no continuity between A and B. It needs a higher current to ionise the neon.


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## phario (May 7, 2017)

Norvin said:


> Its a neon bulb, there will be no continuity between A and B. It needs a higher current to ionise the neon.


 Ah. I see. Stupid, I didn't understand the difference.

So I would have to connect a battery or something to test?

If in the future, we wanted to replace with an LED, is there a particular LED we should be picking?


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## Norvin (Sep 10, 2014)

I would think that you would have to connect to the mains to test although I don't know enough about it to recommend (I now think that it may be PD not current that ionises the Neon).

I would like a replacement myself as the neon bulb in the switch on my OWC has the same problem i.e it works intermittently. Waiting with interest for someone else to answer.


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## jjstorgaard (Jan 19, 2019)

Nice writeup, thank you. I had an issue with what turned out to be a defective resistor a while ago and also wrote a bit about what I found out, although not as in much detail as here. Here's the thread:

https://www.coffeeforums.co.uk/topic/44654-home-making-a-brew-light-for-gaggia-classic/?tab=comments&do=embed&comment=745462&embedComment=745462&embedDo=findComment#comment-745462

JJ


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## phario (May 7, 2017)

jjstorgaard said:


> Nice writeup, thank you. I had an issue with what turned out to be a defective resistor a while ago and also wrote a bit about what I found out, although not as in much detail as here. Here's the thread:
> 
> https://www.coffeeforums.co.uk/topic/44654-home-making-a-brew-light-for-gaggia-classic/?tab=comments&do=embed&comment=745462&embedComment=745462&embedDo=findComment#comment-745462
> 
> JJ


 Darn it. I wish I read your post more carefully (which I had seen in my searching). I didn't catch the reference to the German website. Since I'm not able to edit my original post I'll include it here for others to reference: https://www.kaffeewiki.de/wiki/Reparatur_des_Hauptschalters_der_Gaggia_Classic_Coffee

For reference, do you mind linking us with the replacement bulb that you bought? Also link the spring that you bought?

I didn't quite understand what you wrote about the metal rod:



> The bulb linked to in the video description comes with a resistor, so I replaced the old resistor with a tiny metal rod, like in the video. I don't know if it would be possible to find a tiny metal rod like that to buy, I got my father in law to ask a work colleague to produce one with the old resistor as guidance for the dimensions.


 Where does this occur in the video?

The German website is really excellent. I wish I had it when I started.


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## jjstorgaard (Jan 19, 2019)

Here's the spring that I bought: https://www.ebay.co.uk/itm/2-4mm-OD-2mm-Stainless-steel-compression-spring-up-to-1000mm-long/231460537749?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

The bulb seems to have disappeared from eBay, the product description was the following: Barthelme 000823R0 Coloured Neon Lamps Red 0.25W Ø3.8 x 30mm

I'm pretty sure the yellow sleeve at 10:29 in the video is just for insulation, I suppose so the current doesn't skip the resistor. I'm not sure if I put anything on, if I did it will have been electrical tape.

At 4:04 in the video you can see the tiny metal rod being inserted as a replacement for the resistor, as the replacement bulb used comes with a resistor (which differentiates it from the stock bulb). Since the replacement comes with a resistor, the original one needs to be replaced with a little piece of metal to keep the connection from the spring to the switch. In my case, it turned out that it was actually not the bulb but the resistor that was defective. I don't know how to read the markings on the resistor that was in there to start with (it doesn't have the standard colour code), so replacing with a bulb with integrated resistor plus a tiny metal rod was the easiest option.

JJ


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