VAM/Caravel thermostats - anatomy and issues

#1: Post by **Italyhound** » April 27th, 2014, 1:46 pm

It's hard to break away from the caravel mega thread. I tried to get an electrical thread going, and will try to get a separate discussion going about the thermostats. The assembly changed over time.

I actually have an old VAM and a newer Caravel 2.0. Both of these machines have the same issue, and that is that the element shuts off way before the boiling point. I am going to try and use this thread as a focal point for discussing these different tstats, and their problems since I have them on both.

DrGary outlined his tstat on the Caravel 1.0 here - Thermostat versus PID on a Caravel

Here is a post on calibrating the TSTAT: Caravel Thermostat Problems

Here is an edited to add post that may have relevance to me. Dumpshot and sorrentinacoffee working it out: VAM Caravel - 110v element and powder coat!

I will add other relevant posts as I find them. Feel free to point me to them too.

======

Meantime, here is what my caravel 2.0 looks like. I would like to try and find out where to start getting the tstat to allow the kettle to boil water.

At first the kettle didn't appear snug but after looking at one of the referenced threads up top, I got it snug but the tstat kicks off even earlier now.

The thermostat assembly is here, and is the key to what actually to adjust.

The top of the assembly is where the little adjustment screw (with a spring along the shaft) on the back presses into the bar (located just below the horizontal piece at the top of the photo), allowing it to maintain contact longer and keep the element on. At the moment, this knob position is maxed out, so it is not the answer for me.

In the middle, at the level where the element mounts, is a spring and a screw (pointed downward below the philips head screw holding the assembly to the frame.

At the very bottom is a small flathead screw which attaches to the on/off switch on the rear bottom. When the switch is moved, the rocker moves a little. Looks like there is a spring there too.

So, anyone who has experience here - where do I start?

#2: Post by **danetrainer** » April 27th, 2014, 2:04 pm

Number 1, especially from the evidence in your photos are the electrical connections them-self. High resistance as the result of dissimilar metals, moisture and heat over time are seriously affecting the thermostat to work properly. I would consider the wires, the connections & the mounting point to the metal bar all are suspect. Removing just the wires where they bolt down to the bar and creating a clean connection would not likely be enough to restore its original functionality as the wire to connector crimp will likely be a factor too. It may also be difficult removing the screws without distorting the metal...it all needs to be done with close attention to returning it to "like new" condition.

April 27th, 2014, 2:17 pm

Thanks, Pat

I am an admitted electrical neophyte, but the 'loose' positioning of the bar seems to be behind the problem. If adjusting the right spring could make it 'tighter', it would seem to make contact with the kettle longer.

If the contact were good, and it still kicked off, I would be more suspicious that it was the electrons as the problem.

Am I wrong?

#4: Post by **danetrainer** » April 27th, 2014, 2:38 pm

No, you are not wrong...and the mechanical bar is also affected by the same conditions that have caused the electrical to degrade, ie: the spring is certainly weakened by heat and corrosion, along with the pivot point of the bar. The ideal solution is always to correct all the aspects in the system because it can cause continual fiddling to try and maintain the setting.

My 2.0/2.1 (it seems to be somewhere at the change point in the model) is new/unused other than my testing of essentially the boiling & kettle. It boils readily but has a wide deadband after the thermostat shuts off before it heats again. I turned the adjustment screw on the back as you had done to find it changed little.

You certainly may find that assembly in the lower part with the screw head and spring allows for centering the rear adjustment screw and worth trying.

#5: Post by **drgary** » April 28th, 2014, 12:55 am

Evan,

Thank you for starting this thread. In the Caravel mega thread it's hard to find focused information like this. I'll post a link there to help build out this information.

#6: Post by **drgary** » April 28th, 2014, 1:22 am

The reference site for VAM and Caravel version designations is built and maintained by Francesco Ceccarelli, an Italian collector. His history of the VAM and Caravel is here, including descriptions of the evolving temperature regulation systems of these machines. If you select links of successive models you can see how they changed over time.

Arrarex by Francesco

April 28th, 2014, 11:46 am

OK

So I have made some progress, hopefully enough that someone can pinpoint the issue. I spent the morning with the machine apart and looking at the various things that make that rocker t-stat assembly tick.

I am thinking the issue is at the top where the temperature adjustment screw sits. The end of that screw pushes the rocker forward and, at some point, the element kicks on.

Here is what I noticed:

If the kettle is seated, and the on/off knob is 'on', the rocker is pushed back and it will not kick on the element. That rocker has to be at some forward position to activate, not just pushed on by the kettle.

If the back temperature control is pushed (like a regular button), then the rocker moves forward and the element clicks on.

So, my issue seems to be that my rocker is rocked too far "backward", so it will not start the element. I would think once handily forward enough, then fine adjustments with the temp screw would be possible.

My hunch is it's the temperature screw, and it's little spring - but I am not sure - maybe it isn't feeding tension forward. As I said before, it takes pliers to turn it - that can't be right(? other caravelistas - can you confirm?). I played with the screw at the bottom which connects to the on/off knob. That didn't do anything but stop it from turning it on - at all costs - when the spring was too tight.

Full disclosure, this all started when I used it and it worked but wouldnt come to temp. I may have made my life more difficult now - but not sure how. All I did was play with the 3 springs at the base of the kettle (two in front - 1 behind that attaches to the rocker)

Here is a video of the rocker being pushed forward and then let to drop back. That "click" is the collective sound of the rocker switch clicking and the transformer powering the element simultaneously.

I hope it makes sense to someone. I really do!

April 28th, 2014, 12:45 pm

I had high hopes after finding this post from Jack (sorrentinacoffee) and I had some progress doing what he said.

I now have the rocker positioned so that it will pop on when the on/off switch is turned to the on position. Decreasing spring tension at the very bottom screw behind the on off knob helped get that rocker pushed 'forward' instead of backward. It is definitely as 'see-saw' as it gets with those adjustments.

However, it is still cutting off very very early. If I push the temp screw on top like in the video above, it clicks on. Adjusting the screw doesn't seem to help. The rocker is being clicked off somewhere else.

How to keep that rocker forward, and the element on longer, this is the crux of it!

One thing I am noticing, and this has been talked about with respect to the new elements. The machine frame gets BLAZING hot, to the point where I cant touch the temp knob when it kicks off. I checked the kettle and it seems seated very well.

I have recently worked on several Caravel thermostats. usually I find it is just a matter of calibrating it correctly. You don't need to take many things apart:

1) remove the kettle and base

2) turn the power knob to 'on' position

3) turn the thermostat screw to approximately the middle position- you can see the end of the screw protruding (below the kettle release catch) onto what I will call the 'switching lever'. This is the important part- it is a basic see-saw with the on switch at one end- and the thermostat screw at the other- the fulcrum is at the thermostat switch.

4) when the machine is working correctly- at this time you should be able to able to press both the 'on' knob- and the thermostat screw- alternately- switching the lever back and forth- you should here a definite click as you do this- this is the switching lever activating the thermostat switch. You should hear the same click when you turn the 'on' knob on and off. If you don't here the click- you can adjust the movement of the 'switching lever' via the thermostat screw- and via a small screw located directly behind the on switch- inside the base- above the power cable. You can get a small driver in there without changing any of the wiring. Basically the adjustment should be simple- turn the two screws to try and find the center point and have the switch operating. If there is little movement in the see-saw- adjust it until it start rocking. There may be no click and it seems like the switch is dead- then you hit the sweet spot! Once you get the lovely 'click, click' you know you have it right. Also now the on/off switch should work correctly.

5) Reassemble and test- adjust the thermostat to taste with subtle adjustments only. Allow the machine to cool- then make a small adjustment- retest. I try and set mine so they switch out just after a medium rolling boil.

6) your all cool to go.

DISCLAIMER

if you cannot get a nice click- you have failed- or the switch has failed. I have yet to find a failed switch. Sometimes you need to push on the back of the switch and little with a driver to get it clicking nicely- it seems they may stick with storage. Once unstuck they seem fine.

April 29th, 2014, 10:09 am

My next step to thermostat normality will be to replace the springs as outlined on page 89 of The Arrarex Caravel thread

My rocker seems to be working, and both adjustment screws are maxed out. Something is clicking the switch below the level of the top screw.

In looking at my element, it does not lie flat, and the machine is blazing, and painfully, hot to the touch. This tells me that the element seating and/or kettle position might be awry - causing excess heat to stop the TSTAT or poor kettle positioning.

I am going to hit the store and try new springs. Of the three springs holding the tray, the one in the back where the tray hooks up to is the one which I am unsure of its function. It is the downward facing nut that adjusts on a screw which contains a spring.

April 30th, 2014, 5:17 am

it has been a while since i tinkered with a Caravel thermostat. It can be a tricky business and is very hard to describe.

If you have no joy fine-tuning yours: One thing I do remember from when I used to fiddle with them was that you can adjust the see-saw in such a way that the machine is permanently on. This is not a bad situation: asyou become the machines thermostat and turn it off manually at the power point when it reaches a boil. The bonus here is that you are less likely to forget the machine and leave it running unattended...