Pitot Tube Heat Failure

[tim417]

Is there an option to have the heating element replaced on the PH502-12 pitot tube or is the only real choice replacing the entire thing? Prices on 12v heated pitot tubes are crazy. 

[Skates97]

3 hours ago, tim417 said:

Is there an option to have the heating element replaced on the PH502-12 pitot tube or is the only real choice replacing the entire thing? Prices on 12v heated pitot tubes are crazy. 

Not that I am aware of. I had to replace mine a few years ago and was able to find one on Ebay. 

[tim417]

1 hour ago, Skates97 said:

Not that I am aware of. I had to replace mine a few years ago and was able to find one on Ebay. 

Well this makes me sad. 

[EricJ]

10 hours ago, tim417 said:

Well this makes me sad. 

+1 that AFAIK they're apparently not servicable.    I have one that got removed due to a leak after it wouldn't pass static leak test.    It'd be great to keep as a spare, but I haven't figured out how to take it apart and fix it if it's even possible.

[Skates97]

11 hours ago, tim417 said:

Well this makes me sad. 

I understand...

I have my old one sitting on the shelf but like @EricJ mentioned I don't see how the element comes out if you could even buy a replacement.

[PT20J]

Try calling the OEM  https://www.aerosonic.com/repair-oh.

Dumb question, but did you verify voltage at the pitot tube itself?

[OR75]

not sure why but the 12V are a lot more money than the 24V version 

 

[tim417]

Well, here’s an update. I connected the pitot tube directly to my car battery with a 15A fuse and it heated right up, so that rules out the heat element. I brought my multimeter to the hangar this time and I’m getting good voltage at the connector to the pitot tube (12.5v) but only 3 amps. Checking my breakers, I see that the pitot heat is tied to the AUX BUS breaker which is 40A. I am guessing there is a weak connection somewhere that is robbing some power. 

 

Any suggestions as to where to look? My A&P stopping by the hangar periodically as he has time to check on me but hasnt had time to troubleshoot it directly. Once I isolate the issue will get him to address it. 

Tim

[Fly Boomer]

10 hours ago, tim417 said:

good voltage at the connector to the pitot tube (12.5v) but only 3 amps

Spruce says the AERO INSTRUMENTS AN5812-12 is supposed to pull 8 amps, so something is off.  I wonder if there is circuitry to limit the temperature?

https://www.aircraftspruce.com/catalog/pnpages/AN5812-12.php
 

[MikeOH]

10 hours ago, tim417 said:

Well, here’s an update. I connected the pitot tube directly to my car battery with a 15A fuse and it heated right up, so that rules out the heat element. I brought my multimeter to the hangar this time and I’m getting good voltage at the connector to the pitot tube (12.5v) but only 3 amps. Checking my breakers, I see that the pitot heat is tied to the AUX BUS breaker which is 40A. I am guessing there is a weak connection somewhere that is robbing some power. 

 

Any suggestions as to where to look? My A&P stopping by the hangar periodically as he has time to check on me but hasnt had time to troubleshoot it directly. Once I isolate the issue will get him to address it. 

Tim

Not sure I'm following...is the 12.5V you measured at the pitot heat connector open circuit (connector unplugged from the pitot)?  Or, is that while power is being applied to the pitot heater?  It would be very odd to have only a 3A draw AND the full 12.5V.

I would look at the pitot heat switch first; try jumpering around it to see if you then get full pitot heat current.

I'm assuming in all of this that, based on your test with the car battery, the pitot heater itself is now known good.

[EricJ]

12 hours ago, tim417 said:

Well, here’s an update. I connected the pitot tube directly to my car battery with a 15A fuse and it heated right up, so that rules out the heat element. I brought my multimeter to the hangar this time and I’m getting good voltage at the connector to the pitot tube (12.5v) but only 3 amps. Checking my breakers, I see that the pitot heat is tied to the AUX BUS breaker which is 40A. I am guessing there is a weak connection somewhere that is robbing some power. 

 

Any suggestions as to where to look? My A&P stopping by the hangar periodically as he has time to check on me but hasnt had time to troubleshoot it directly. Once I isolate the issue will get him to address it. 

Tim

How did you measure the current?     Measuring the voltage at the heater while current is flowing will tell you whether there's a voltage drop elsewhere (e.g., the switch) that might need to be addressed.

FWIW, in many Mooneys the switch is the breaker.   On a J model the pitot heat switch is a 10A breaker.

3A at 12V is 36 Watts, which will still get plenty hot.   Think of grabbing a 40W light bulb after it's been on for a while (old people example).

[tim417]

Latest and final update. My tech came by and found a weak connector in the line and rewired with new terminals. He also found that one of the terminals at the switch was loose. Once that was tightened, he hooked it all back up to test and the tube heated up immediately. 

 

Good reminder to check the obvious things first 

 

Tim

[Jim Peace]

Just curious if you gave it enough time to heat up.  This is not the pitot heat quality you see on jets.  Mine takes a while from the time you put the switch on but it does heat up eventually.  

[OR75]

14 hours ago, Jim Peace said:

Just curious if you gave it enough time to heat up.  This is not the pitot heat quality you see on jets.  Mine takes a while from the time you put the switch on but it does heat up eventually.  

I believe it actually should heat up fairly fast (feels warm within seconds the switch is turned on)

[PT20J]

Mine heats up enough within a minute to burn your hand if you were to grab it. Are you sure someone didn't mistakenly replace it with a 28V unit? Or, maybe there is a bad connection somewhere (which would be a problem because if it's dropping voltage enough to affect the pitot heater, it's probably getting hot).

[MikeOH]

Uh, you guys realize the OP got it fixed, right?

[tim417]

12 hours ago, PT20J said:

Mine heats up enough within a minute to burn your hand if you were to grab it. Are you sure someone didn't mistakenly replace it with a 28V unit? Or, maybe there is a bad connection somewhere (which would be a problem because if it's dropping voltage enough to affect the pitot heater, it's probably getting hot).

Yes, it turns out it was a loose terminal at the toggle switch on the panel. Two seconds with the flathead and thr issue was resolved. I love my tech buddies.