A question in the round, TB 20: Conversion of the old oil pressure gauge to Aerospace OL 100.
Is it a good idea to eliminate the red alarm lamp to indicate low oil pressure?
Or is it better to reconnect this lamp?
Thomas wrote:
A question in the round, TB 20: Conversion of the old oil pressure gauge to Aerospace OL 100.
Is it a good idea to eliminate the red alarm lamp to indicate low oil pressure?
Or is it better to reconnect this lamp?
That depends on conspicuity of the lamp and the oil pressure instrument and whether there is a master warning light.
Does the red alarm lamp has its own low pressure sensor? The alarm lamp and the oil pressure instrument should agree on what is a warning situation.
In any case, if you don’t reconnect the lamp you should remove it. (Or cover it.) Of course, there may be regulatory requirements to keep the lamp.
I would not remove it because it has its own switch so is a standalone indicator with no dependencies.
The OL100 is a microprocessor based box so basically you can’t trust what it says by itself 
< anal mode on >
I would also be surprised if it has an STC for a TB20 which requires the removal of the oil pressure lamp and switch. And if you remove the switch then the STC needs to contain instruction on how to plug the hole.
< anal mode off >
Out of interest, where does the OL100 pressure sensor install? I’ve been around this loop, with a backup oil pressure gauge, and it isn’t trivial.
The great thing is that I have owned this TB 20 for 10 years. My preparation before starting the engine I press the test button
to check the indicator lights. everything is in order the red oil lamp lights up. 2 weeks ago I noticed that the oil pressure switch was leaking a bit.
It exits through the switch adjustment screw hole. Apparently the membrane of the switch is leaking.
A closer look at the function told me that the low oil pressure switch works perfectly (on and off) but the wrong way and it is not connected to the red alarm lamp.
This alarm is out of service. I assume it was done during Aerospace Ol 100 installation. This plane works in this way for more than 10 years, it is worth changing
anything? I could easily do it. Purchase a new low oil pressure switch which works in the right direction and reconnect it to the alarm lamp.
What I don’t know is whether the new OL 100 device has an alarm function as well?
I will try again. Is there anyone in the group with a TB 20 and with a device Aerospace OL 100 oil indicator and the
ALARM RED LAMP in front of your face? Does your TB 20 still have the red light and does it work together?
I understand nobody wants to see the lamp in flight. But that’s why it’s so important to know if it works.
I found the OL100 STC here.
It is certified as primary for the TB20 so you could remove tht oil pressure lamp and its pressure switch. But why would you want to?
The OL-100 is very old and discontinued so I can’t find an installation manual, but other manuals here are completely useless, so I wonder how this one was installed. What year is your TB20?
Hi Peter,
thanks for your effort again.
Here a picture. These indictors was installed 2010 and I’m very happy.
I have two Low oil pressure switch and one oil pressure sensor in my
plane. The sensor is conneted to OL 100 Unit and works properly.
But the 2 Switches work as well but they are not conneted to the
Red Lamp. I found this curios in regarding to the oil leaking.
In the past I have never seen the red alarm light go on. Only by test button I could see the lamp went on.
There are 2 ways: I remove both Low switches and am happy
with my OL 100 indicator or for more comfort I install the
the Low oil pressure switch and connect it to the Red Lamp.
Sounds like somebody disconnected the red low oil pressure warning lamp ut left it in the panel. You should get it reconnected.
I am sorry but I can’t get my head around what somebody has done. It sounds really stupid, but nothing surprises me in GA
You have two oil pressure switches and neither does anything!
The test button does nothing; it just applies power to the lamp.
To be continued for anyone who is still interested.
I installed a new low oil switch ( NPT 1/8 -27, alarm pressure 0,8 bar) and connected it to the panel.
This switch works reverse to my old one. But now appropriate to the function of the TEST SWITCH at the panel.
Without pressure the red lamp lights up and when the engine is running and there is pressure in the system, the lamp goes out.
I hope I don’t have to experience with the red lamp during a flight.
Without pressure the red lamp lights up and when the engine is running and there is pressure in the system, the lamp goes out.
That is how the switch is supposed to work.
I can’t believe somebody was messing about with this stuff and did it backwards, then sold the plane. And a prebuy didn’t pick up that there was a permanent oil pressure warning.
