[Kent Shaw]

Kent Shaw on May 14, 2022 at 2:24 pm #21399

First check all the defroster scat hoses for cracks and brakes. Next, check operation of the defrost cable. If it is broken or disconnected, you may need to order a new cable or fix the connector hardware. If you need new hoses, check out this guy. (sorry, this referenced an outdated link which has been removed. 

[STEVE]

STEVE on March 16, 2022 at 11:12 am #21284

Hi Rod;
I don’t know if you did this and didn’t write it down, but from your write up I wonder if you checked to determine if the pressure you plugged into the air inlet hole in the cowling was getting to the heater vents below the windshield when the hoses from the “muffler” were attached to the defroster control slider boxes?
Is it possible that something is blocking the tubes between the defroster control boxes on the firewall and the defroster vents at the windshield??
Let me know what you find,

Steve

[STEVE]

STEVE on March 16, 2022 at 11:12 am #21285

Hi Rod;
I don’t know if you did this and didn’t write it down, but from your write up I wonder if you checked to determine if the pressure you plugged into the air inlet hole in the cowling was getting to the heater vents below the windshield when the hoses from the “muffler” were attached to the defroster control slider boxes?
Is it possible that something is blocking the tubes between the defroster control boxes on the firewall and the defroster vents at the windshield??
Let me know what you find,

Steve

[Rod]

Rod on March 13, 2022 at 8:04 pm #21281

Hi Steve. Thanks for the reply and the advice. I pulled the hoses and inspected the slider valves. Everything functions correctly and the holes in the slider plates align perfectly when the defroster control is in the full on position. I blew air back through both hoses into the heat muff, and they appear to be unobstructed. Finally, I attached a hose from the exhaust of a shop vac to the air inlet for the heater in the cowling. I got good airflow through the defroster hoses with them unattached from the slider valves, so it appears the entire system is working normally. While flying the airplane the other day, I turned the heater control off and the defroster on. I was not able to detect any hot air coming out of the defroster vents. I’m beginning to think the defroster is under-designed. I get lots of hot air from the heater when it’s turned on.
Thanks again for your input.
Rod

[STEVE]

STEVE on February 19, 2022 at 1:01 pm #21253

Hi Rod;
There should be more than sufficient heat to clear (most of) your windshield from your defroster system.
Both the cabin heater and the defroster system use heat that’s picked up as ram air is ducted around what looks like a muffler on your exhaust system.
If there’s sufficient cabin heat, there should be sufficient defrost heat.
As an experiment, see if lessening or turning off the cabin heat increases the effectiveness of the windshield heat.
Yes, it could be that one of the flexible tubes (Aero Duct tubing) is blocked or collapsed, or that one of both of the on off valves in the defroster system are rusted to the point the flapper valves no longer move.
Of the wire from the defrost on-off valve is broken.
These discrepancies are pretty easy to troubleshoot.
As an aircraft owner, you can legally remove the top cowling and take a look at the various tubes and valves in the defrost system. Most of the parts are forward of the firewall. Take off each AeroDuct and check for obstructions. Clean the tubes and re install them.
Move the defrost on off control to max heat and check to see that the flappers in the valve box move. Lube the pivot points with LPS 2.
If the flappers don’t move when the on off control is moved, your mechanic will need to take a look and will most likely have to get a new control wire and housing.
Take a look and let me know what you find.
Thanks,
Steve

[Rod]

Rod on February 14, 2022 at 6:22 pm #21246

I was flying practice instrument approaches in IMC conditions (ceiling broken 1800) in an Arrow III and picked up a small amount of ice. Airframe icing was negligible, but the windshield iced over except for a small area in the lower left corner. I had the defroster turned to its full on position, but it was totally ineffective. Temperature on the ground was about 36F, so I terminated my approach with a full stop landing and waited on the ground until the ice melted off the windshield, then returned to my home airport VFR. I am wondering if the defroster in my airplane is not working properly (obstructed hoses perhaps?) or if it is merely inadequate. Has anyone else had a similar experience, and is there a solution?