Looking for a otter switch

[AC Ace Bristol]

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   Robin.
   
   Don't throw your toys out of the Pram............
   
   It is only the select few ACOC Members who use the Forum, many have still to master time travel and enter the 21st Century.
   So let's buy a couple of months and advertise in the next issue of ACtion and see response []..........No, No!! not another Fuel Filler Cap SAGA...[B)]..
   
   Seriously, It is one of those items required by many but not readily available, May I suggest that you continue with your prototype and hopefully a small batch run will be viable and appreciated by many..ACOC members and AC Enthusiasts[]
   If a positive response then I will put the project forward at suitable ACOC Council meeting..to help financially..[]
   In the meantime I will speak to Terry Webb regards letter and pictures in ACtion .....Good Luck with the prototype..[^]
   
   Keith...[]

[Robin A Woolmer]

Keith
   I am afraid my pram was disposed of many years ago probably to make Spitfires!
   I will complete what I have started in respect to making a sample Thermostat, so we will see!
   There is one issue, my thermostat is open & makes contact (closes) @ temperature which appears not to conform to the ACE handbook description of the operation, it would help if somebody would confirm if the switch should be normally open or closed!
   Robin

[B.P.Bird]

Robin,
   Closed at ambient temperatures, open at elevated temperatures. So we need to know the trip out temperature ( it must be quite low, 30 or 35°C ?) There are other Otter switch patterns doing the same job - notably in Jaguars with the starting carburetter so maybe Otter would know ? As I understand the electrics the starting carburetter solenoid has 12v supply from the ignition loads and the Otter switch is in the earth connection. Thus, with a cold engine, there is a circuit and the starter carburetter is in operation as soon as the ignition is switched on - there is an audible click as the solenoid opens the starter carburetter feed. As the engine warms the Otter switch goes open circuit and the starter carburetter drops out. You will notice the obvious weakness in the system in that it is fail dangerous. See Ace and Aceca  General Instructions page 22 and 23.
   I would offer to check my switch to get an open circuit temperature, but as it is at least 60 years old there might be some variation from original specification.....
   I would put a couple of spares on the shelf if that is any help.

[Robin A Woolmer]

Barrie
   Thanks for the information, your description aligns with the Car Manuals & is basically a fail safe circuit so it does not run rich if a failure of the switch, I can get either type switches so is not a problem, the information I have is that the switch operates at 35 degrees centigrade with just over one Amp to operate the solenoid!
   I do not know why my switch (the one in the picture) I have is open normally & closes on temperature!
   
   Regards
   
   Robin

[Flyinghorse]

Robin,
   One explanation is car earthing polarity (ie positive earth changed to negative) may have been changed,but otter left the same?
   Graham

[B.P.Bird]

Graham, nought out of ten for 'O' level Physics - polarity would make no odds to current flowing - the Otter switch opening would still break the circuit. I rather suspect the switch Robin has is far from well and is operating in reverse; they are temperamental things if dropped or tweaked. The failure mode of course depends whether or no the switch cooperates and opens at 35°C. If it fails to open then you run too rich, whilst if there is an electrical failure the starter carburetter drops out. There is a lot to be said for an on/off switch and a nice bright warning light - a solution often adopted in period. However an original solution is the best aim so well done Robin.

[nikbj68]

To compound the issue, I couldn`t find anything at the NEC autojumble, but a couple of helpful souls suggested contacting Burlen.
   Must away to my pillow... it has been a loooooooooooooooooooong weekend!(But V enjoyable!!)

[Robin A Woolmer]

Have ordered a thermostat switch of each type, open normally also closed normally, so we can test either type, one point when cars are in high ambient conditions I would suggest that an over ride switch as indicated earlier would be needed, fortunately or unfortunately this is not normal in UK!
   It will be a couple of weeks before I receive the sample thermostats & will then have some housings made to fit them into for testing, we then need a volunteer to test them as I do not have a car fitted with these enrichment devices!
   
   Robin

[Robin A Woolmer]

I now have the sample Otter Thermostat which is set to 35 degrees Centigrade plus or minus two degrees, I also have designed & had made a few housing plates into which the thermostat will be fitted & held in with a shouldered screw, I will machine the cavity for the switch & fit the switch next week.
   Ian Mahany has agreed to carry out a test on the thermostat for me & subject to that being successful will then get some costing's together, it should be realised that there are minimum charges to make special parts & some work time needed to machine & assemble the parts!
   It might be best for the Club to take on the manufacture of a batch, I anticipate that at least thirty switches should be made due to minimum charges for parts, what is essential are how many will be required/ordered so it will shortly be up to you guys to make some commitments / recommendations on this matter, I will take some pictures of the final assembly & will arrange for a short article to be put in AC Action!

[Robin A Woolmer]

The sample Otter Switch is now made & will be tested by Ian Mahany for me shortly, Nik has been requested to put some pictures on the forum for me so you can see how it is, I anticipate the production types will be bonded into the housing as well as having the clamp screw to hold the thermostat into the plate.
   It will be noticed that the wiring consists of wire tails so if you have them you will need to terminate them with a suitable connector!

[nikbj68]

The photos of Robin`s sample:
   
   
   
   
   
   
   
   
   
   
   
   

[Robin A Woolmer]

I understand the new Otter Controls Thermostats are now available in AC Spares, these are the new design as described in the April issue of AC Action, these are very simple to fit as described & can be purchased from the Club Spares.
   
   I hope this solves any problems for you.
   
   Robin