I'm trying to puzzle out the electrical system in my Hatz. Specifically, why I'm having trouble cranking the engine (O-290, old style Delco starter, Odyssey PC680 battery). The battery was new this past fall, but I'm suspecting there may be multiple issues.
The battery is behind the seat, the master relay is near it, then there's a long cable going to the engine compartment where the starter relay is. I've been keeping the battery on a trickle charger (one recommended by Odyssey) since early December.
I've had battery issues before, including one verifiably bad battery. When the engine fails to crank (cranks real slow, then won't get over compression), the pinion stays engaged (apparently normal for this type of starter) so it can't be hand propped. In this situation, I clip a portable jumpstarter battery to the battery side terminal on the master relay (because it's conveniently accessible in the cockpit) and to a stud on the fuselage frame, and it has always started.
Today, however, it did no better on the jumpstarter than it did on the aircraft battery. I then connected the jumpstarter to the battery side of the starter relay, and it started right up, indicating I have a problem with either the master relay or the heavy cable between it and the starter relay (or with the battery ground wire, but I checked that and cleaned the terminals last fall). I didn't have a voltmeter with me to do any measurements today. The master relay seems a likely culprit, so I tried to figure out what it is, and now I'm more confused than ever.
The heavy wire on top to the BAT terminal goes to the battery, the white wire on the same terminal goes to the master switch, and the green wire goes to the other contact on the master switch (the red wire is a connector for the trickle charger). The white wire on the mounting bracket is grounded to the fuselage frame.
The part number looks like 70-111225 5, which is a valid White-Rodgers part number... but according to the White Rodgers datasheet, the 225 has two coil terminals but mine has only one.
Now, maybe those 5's are really 6's, the 226 does have a single coil terminal, but they look the same and 6 isn't valid in the last position. Aircraft Spruce sells the 226. BUT... if the coil is internally connected to the BAT, it can't possibly work because the green wire to the coil terminal is being fed +12V from the master switch. Note also that the 226 has an angled coil terminal, whereas on mine it's 90° from the contact terminals.
This is the schematic drawn by the original builder, which agrees with what I can see:
The only thing I can think of is maybe an earlier version of the 225 had a single terminal with the coil grounded to the case, instead of the "Coil terminal with ground wire" as in the current datasheet???
Regardless, it looks like I'd have to replace it with a 225 with the external ground, or the more available 224 (which appears to be the same thing without the supplied ground wire, which is trivial to add). Neither of which ACS supplies and the 225 is hard to find, but the 224 is readily available from various suppliers.
The alternative, which seems to be a more common setup, is to use a 226 and rewire the master switch to ground the coil terminal instead of supplying +12V to it. Certainly I could do that, but I'm open to input on why one approach is better than the other. Unless I'm missing something obvious?
The battery is behind the seat, the master relay is near it, then there's a long cable going to the engine compartment where the starter relay is. I've been keeping the battery on a trickle charger (one recommended by Odyssey) since early December.
I've had battery issues before, including one verifiably bad battery. When the engine fails to crank (cranks real slow, then won't get over compression), the pinion stays engaged (apparently normal for this type of starter) so it can't be hand propped. In this situation, I clip a portable jumpstarter battery to the battery side terminal on the master relay (because it's conveniently accessible in the cockpit) and to a stud on the fuselage frame, and it has always started.
Today, however, it did no better on the jumpstarter than it did on the aircraft battery. I then connected the jumpstarter to the battery side of the starter relay, and it started right up, indicating I have a problem with either the master relay or the heavy cable between it and the starter relay (or with the battery ground wire, but I checked that and cleaned the terminals last fall). I didn't have a voltmeter with me to do any measurements today. The master relay seems a likely culprit, so I tried to figure out what it is, and now I'm more confused than ever.
The heavy wire on top to the BAT terminal goes to the battery, the white wire on the same terminal goes to the master switch, and the green wire goes to the other contact on the master switch (the red wire is a connector for the trickle charger). The white wire on the mounting bracket is grounded to the fuselage frame.
The part number looks like 70-111225 5, which is a valid White-Rodgers part number... but according to the White Rodgers datasheet, the 225 has two coil terminals but mine has only one.
Now, maybe those 5's are really 6's, the 226 does have a single coil terminal, but they look the same and 6 isn't valid in the last position. Aircraft Spruce sells the 226. BUT... if the coil is internally connected to the BAT, it can't possibly work because the green wire to the coil terminal is being fed +12V from the master switch. Note also that the 226 has an angled coil terminal, whereas on mine it's 90° from the contact terminals.
This is the schematic drawn by the original builder, which agrees with what I can see:
The only thing I can think of is maybe an earlier version of the 225 had a single terminal with the coil grounded to the case, instead of the "Coil terminal with ground wire" as in the current datasheet???
Regardless, it looks like I'd have to replace it with a 225 with the external ground, or the more available 224 (which appears to be the same thing without the supplied ground wire, which is trivial to add). Neither of which ACS supplies and the 225 is hard to find, but the 224 is readily available from various suppliers.
The alternative, which seems to be a more common setup, is to use a 226 and rewire the master switch to ground the coil terminal instead of supplying +12V to it. Certainly I could do that, but I'm open to input on why one approach is better than the other. Unless I'm missing something obvious?
