Trouble with Baso pilot safety switch

Very old forced air furnace has thermocouple sitting in continuously lit pilot light. End of tcpl "wire" is screwed into a Baso pilot safety switch, model 850. It appears that the current from the tcpl energizes a small solenoid inside the Baso. I could not get the Baso to stay in the on position so this evening I replaced the tcpl, eventually twice. The first one worked for one cycle of the furnace, then the Baso tripped and could not be reset to on. I then installed the second tcpl, and it will occasionially let the burner gas come on for about a second, before the Baso would trip.
I can think of four possibilities as to what's wrong.
1. The Baso needs replacing. The only reason I haven't done it is that it is $90 and I can't see anything in it that could fail. It appears to be extremely simple.
2. The pilot is under driving the tcpl. It gets the last 1/2" up to medium red.
3. I have a bad connection where the tcpl is screwed into the Baso.
4. The pilot is overheating and killing the tcpl.
I would appreciate if you would please hold the comments that any furnace with a pilot safety switch is an inefficient dinosaur and must be replaced. It is in an area with extemely moderate weather and our gas bill is less than $40 monthly in the middle of the winter, including gas water heater and stove. Thus, the break-even date on a new more efficient furnace would be... never. And, I like equipment that you can fix with a large hammer.
Any ideas as to what's wrong?
Henry
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You are not burning out the thermocouple that fast, 4 is not the answer. Do you have a millivolt tester. The thermocouple should be putting out 30 mV if you huld down the reset button to keep the pilot burning and test the baso end of the thrermocouple. 20 mV should be enough, but thermocouples are rated 30 mV.
If you SNUG the conncetion at the BASO with a crescent wrench, you should rule out #3
If you can adjust the plot flame to be a little bigger with the needle valve, that will take care of #2
That leaves #1 and the possibility that you are buying cheap home center thermocouples that will never be reliable.
If this does not help, call a compentent contractor or buy a honeywell thermocouple tester to test the thermocouple. A digital meter won't do it because it puts no load on the thermocouple. The analog Honeywell meter will add some load to the circuit and give you a better answer. Or call a competent contractor.
Stretch
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Attaboy, Stretch...
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It was # 1. Today I bought a genuine Baso, very heavy duty tcpl. It mounts solidly to the pilot support bracket using a compression nut, so gets a much better cold source too. It cost $18, several times the cost of a Home Depot tcpl. But it was worth many times the extra money - it'll probably outlast the house.
H
HeatMan wrote:

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hey henry,
what place has a $40/month heat bill?
I want to move there!
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Small house in deep wind-sheltered canyon in Los Angeles. No insulation in attic. Heating is cheap but houses are expen$ive! Move-in also includes earthquakes and Governor you could swear you've seen somewhere before.
Henry
cowboy wrote:

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Hi Henry, hope you are having a nice day
On 20-Jun-05 At About 03:50:28, Henry wrote to All Subject: Trouble with Baso pilot safety switch
H> Very old forced air furnace has thermocouple sitting in continuously H> lit pilot light. End of tcpl "wire" is screwed into a Baso pilot H> safety switch, model 850.
That's an oldy alright :) the problem is that I am not there to take the needed readings and do the tests. you really should call someone local to check this for you as it could be any one of several things you did and didn't list here.
-=> HvacTech2 <=-
.. Pilots are just plane folks.
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ys751 wrote:

Thermocouple produces millivolt range of electricity. It shoulce make a clean tight connection at the valve end. Also you can adnust pilot flamer size. There must be a adj. screw hiddin upder a cap on the main valve. If you have a meter, you can check the pilot driven solenoid coil. Good luck.
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