Hello,

The other day the thermofuse on my old Gaggia Classic blew.

I also noticed that one of the female spade connectors on the upper 145 C thermostat has melted out and burned a bit black.

Am I correct in guessing that both problems are likely related, and possibly due to a loose connection on the female spade connector attached to the upper thermostat?

I believe I need to replace:
(1) both female spade connectors on the Thermostat (the
second connector is not melted but slightly discolored brown),
(2) the 145 C Thermostat (which has one blackened terminal),
and of course
(3) the Thermofuse SKU 309

Does this seem right? Any other recommendations I might be missing?

Any recommended budget crimping tools (& tips) for the spade connectors?

I've done a number of repairs on this old second hand machine -- my 10 yr old daughter was teasing me the other day that I should have bought a new one and saved myself some money. But to be honest I've enjoyed the task of figuring things out.

Thanks in advance for your help.

Tom

Hi Tom -
I have an old Classic and went through a very similar thing (replacing top thermostat and thermal fuse). I didn't have a problem with the connectors, but if I did, I would probably just solder them so that I could have an espresso the next morning, and as I'm lazy. The thermostats are pretty simple, so I don't think you'll need to anticipate this problem cropping up again soon.
Have fun!
S

Does this seem right? Any other recommendations I might be missing?

I think you've done a good job figuring it out and have got it about right. A thermofuse will only blow in case of over heating. Thus, the thermostat probably stuck on. It might have done this on its own, or, as you hypothesize, a loose connection on it could have caused local heating which led to its demise, it then stuck on and the element overheated as a consequence. Here's a few hint and tips.

When you replace the primary connectors, do not solder, with all due respect to the other poster. Connectors in and around heating circuits are only crimped or spot welded, never soldered. The melting point of solder is low enough that it might contribute to a subsequent problem. When replacing connectors in high current circuits, especially those that may have overheated, it is imperative when stripping to cut back the wire until you see fresh, clean copper. When a lose joint overheats, it sometimes anneals the copper. Left long enough in fault, the copper will turn to powder. This effect can take place under the insulation even several inches back from the original joint. If the wire is degraded, you cannot make a proper joint to the new terminal, and the repair will not last. If there is not enough wire, you may have to replace it. Should this be necessary, it is proper practice to replace the whole piece if possible, not just splice on a bit, as you want to keep the number of joints in a high current circuit to the minimum.

As for connectors, buy good ones, not department store ones. There are a lot of really crummy connectors, usually supplied in Chinese kits for the homeowner. The same goes for the crimper. While I can appreciate you don't want to spend a ton of money on a crimper, high current circuits should really be done with ratchet-type crimpers, not the ones that look like skinny pliers. Whichever crimper you use, give the connector a good tug to be sure it's solidly attached...don't rely on how it looks.

Thanks for the tips. Got the parts, installed them, and everything working fine again. Plenty of advice concurs that crimping, not soldering, is the correct method.