DokuWiki Instructions (local)
DokuWiki Manual
Site Checker (Orphans Wanted)
This is an old revision of the document!
On the Challenger 604, the forward Drain Mast heater is electrically open. The symptoms reported by the crew are that the circuit breaker keeps popping. Perhaps this is caused by an electrical wire internal to the heater shorting to ground.
| Heated Drain Mast | 115677-114 | Electrofilm Mfg. Inc. |
|---|
We are now trying to obtain a replacement Drain Mast heater.
Note that while this schematic page is excellent, what is absent from the drawing is that Pin B1 on the relay is actually connected to Pin c (lower case, with bar), which connects to “L” in a hex shape and then to multiple line heaters via two terminal blocks.
The relevant circuit breaker (probably not defective): 7274-11-7 1/2 Klixon, 7.5 amp. The schematic specifies that the expected draw is .96 amps. There are two Drain Masts. The forward was open, and the rearward was about 64 ohms (about 100 ohms expected). This circuit breaker supplies 115V at 400 Hz.
Discovered that there was a line heater for the Water Valve (FILL SOLENOID, see schematic below), located in the cargo hold area, right side, that was shorted against a bolt. Severe charring was present.
For the aircraft to be flyable, awaiting the acquisition of a replacement line heater, we disconnected the lead going to the line heater, and also clipped that wire near the point it connected to the heater, and removed the line heater. Tied back the lead with crimped-loop and zip tied to wire bundle.
Tested by powering the aircraft, resetting 7.5 circuit breaker. Jumpered temperator sensor to ground to activate relay required because temperature was not below 40 degrees, and the aircraft is not in the air). System seems stable, aft drain mast is obviously heated, measured by feeling it from outside.
We invited David Hill to assist with the repair. In preparation of this, prepared the following notes, which describes some of the steps taken.
[typed 9/25/2019] Disconnected Forward Drain mast connector at J11. Heater (white to White/Blue) measures open. (Unpowered, relay off) Measured resistance in connector, which measures resistance of Aft Drain Mast, measures 64 ohms.
Pilots noted that Drain/Line Heater circuit break popped during flight. Likely because “Gnd In Air” activated relay K16.
Powered system. Disconnected connector Thermal Switch connector J31. Jumpered across the two pins. Jumpered J31 connector pulls diode cathode to ground. With Forward Drain mast connector disconnected, Drain/Line Heater circuit break pops immediately.
Disconnected After Drain Mast Heater at J21. Repeated same test as above, with Powered system, and Jumpered connector J31, Drain/Line Heater circuit break pops immediately.
Searched and cannot find J103, or Relay K16. Assuming it is in “Cabin Control Accessory Unit”, schematic Drawing 34-138W021 says it is in “Lower Galley” because relay K17 is in the Cabin Control Accessory Unit, and because J103 (which has about 40 pins) is shown as connected to K16, and also to the Cabin Control Accessory Unit.
Circuit breaker only pops when relay K16 is activated.
Suspect J103 has damage around pins a, b, or c. Or Relay K16 has unused pin B1 grounded or is otherwise damaged.
David came today to help with the Challenger 604.
We looked at additional locations, including in the tunnel, and in the closet. While my brother was looking in the closet, I was bored and looked in some of the drawers. Noticed when looking in the ice box that there was a panel with screws in the corners. We removed this, and the relay panel was inside.
Relay Panel Location
Relay K16 Closeup
Looked at relay K16. Some relay info It functions correctly. Took home, measured fine - checking for shorts. Noticing that even when powering with 25 volts, less than the 28 rated, it is getting quite warm, so going to run it for a while to see if internal shorts develop. Draws about 76 mA.
But what seemed to be the root cause is that on pin B1 of the relay, which connects through J103 pin c, there was a 16 ohm load. This was unexpected.
But when we looked at the schematics, discovered that this is connected to a line heater. The schematic for the Drain Mast doesn't show anything connected to pin c, or relay B1.
This probably accounts for the circuit breaker blowing.
Schematic showing wiring for Line Heaters. The heater which was shorted to the bolt is called “FILL SOLENOID” wire 1WTR017H18. The terminal block called “1WTR TB2 LAV VANITY” is actually located in the panel at right of Cargo Hold. Wire with a “L” in hex shape goes to the K16 Relay, Pin B1, via wire c.
The rear drain mast was a 64 ohm drain
Drain Mast:
64 ohms 1.79 amps 207 watts
Pin C (originally thought was one line heater, but schematic shows various line heaters)
16 ohms 7.2 amps 827 watts
What we didn't know at the time we measured the resistance is that Pin C is actually connected to about 8 line heaters shown in the schematic. The “FILL SOLENOID” heater was shorted to ground.
[9/26/2019] Brother opened right-hand wall of cargo hold, exposing some of the plumbing for the cabin water supply.
A terminal block is present. Measured resistance of each of the 5 wires to ground, found one, H1B, that had low resistance, approximately 30 ohms. On close examination, noticed that the wire went to wiring that was wrapped into foam insulation. When opening it, found charred ribbon heater end. Measured resistance, and noticed that movement cause resistance to fluctuate. Looked under heater end, saw that it touched sharp nut point, which was also charred.
According to other references, the unreadable part number was probably 3043-110-6-621.
Ebay possible match: https://www.ebay.com/itm/NOS-Gulfstream-P-N-3043-110-6-21-Heater-Ribbon/263828284040?hash=item3d6d642288:g:qZgAAOSwLB9bU49w:sc:USPSFirstClass!98055!US!-1&autorefresh=true
