Although I'm no expert on electricity, when Dr. Pepper's first mate told me that the cabin light in the head wasn't working I thought that changing the bulb would be a quick fix. But no dice.
Dr. Pepper is a Cape Dory 28 that's old enough to vote.
After an investigation with a multi-tester, here are the symptoms.
All the other cabin lights work.
The light fixture in question works when hooked up to any other twelve-volt source.
The wires leading to the fixture show thirteen volts on the multi-tester.
But these wires connected to the this fixture do not work.
My only theory is that the wires show sufficient charge, but are corroded to the point that they can't carry enough current to power the bulb. Is this possible? Any ideas will be appreciated.
everett@megalink.net
s/v Dr. Pepper's 12 volt mystery
Moderator: Jim Walsh
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D. Stump, Hanalei
Re: s/v Dr. Pepper's 12 volt mystery
Mike,
Last year I removed all the cabin lights from Hanalei to take them home, disassemble them, buff them and re-lacquer them. They came out like new! When I put them back, one thing I noticed was that CD used a silicon grease to seal the connections from moisture. The stuff was really tenacious! Maybe the problem is just a poor connection. I don't know what you could use to remove the silicon. Maybe some acetone would work. But, from what you describe, it sounds like a poor connection. Maybe you could cut the wire back a little, but there isn't much there to work with. FWIW...
Dave Stump
Captain Commanding
s/v Hanalei, CD-30
Last year I removed all the cabin lights from Hanalei to take them home, disassemble them, buff them and re-lacquer them. They came out like new! When I put them back, one thing I noticed was that CD used a silicon grease to seal the connections from moisture. The stuff was really tenacious! Maybe the problem is just a poor connection. I don't know what you could use to remove the silicon. Maybe some acetone would work. But, from what you describe, it sounds like a poor connection. Maybe you could cut the wire back a little, but there isn't much there to work with. FWIW...
Dave Stump
Captain Commanding
s/v Hanalei, CD-30
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Walt Bilofsky
Re: s/v Dr. Pepper's 12 volt mystery
Open-circuit voltage shows a connection, but doesn't, as you note, show whether the connection is capable of carrying much current. This would be dependent on the resistance in the circuit.
To find the problem, disconnect the battery. Turn the light switch on. Then use your multi-tester to measure the resistance between the 12v prong in the bulb socket and the positive battery leads, and also between the ground prong and the battery ground. If you see a high resistance in one side or the other, that could be the problem. To find the source, move one lead of the multi-tester to a point closer in the circuit to the other lead, see if the resistance is in the skipped-over portion or not, and repeat until you have isolated the problem.
A ten watt 12v bulb has a resistance of roughly ten ohms, so if you see a resistance of more than a few ohms it is significant.
This won't always work because some connections might not show much resistance until they are carrying current. You can trace these down by doing the same thing with the circuit hot and measuring voltage.
bilofsky@toolworks.com
To find the problem, disconnect the battery. Turn the light switch on. Then use your multi-tester to measure the resistance between the 12v prong in the bulb socket and the positive battery leads, and also between the ground prong and the battery ground. If you see a high resistance in one side or the other, that could be the problem. To find the source, move one lead of the multi-tester to a point closer in the circuit to the other lead, see if the resistance is in the skipped-over portion or not, and repeat until you have isolated the problem.
A ten watt 12v bulb has a resistance of roughly ten ohms, so if you see a resistance of more than a few ohms it is significant.
This won't always work because some connections might not show much resistance until they are carrying current. You can trace these down by doing the same thing with the circuit hot and measuring voltage.
bilofsky@toolworks.com
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Lyn Heiges
Re: s/v Dr. Pepper's 12 volt mystery
Mike,
Our CD28 (1981 # 307) is also old enough to vote!
The problem could be the switch on the fixture which no longer functions. I had this happen to the portside V-berth fixture on our CD28. I had replaced a similar fixture on my previous CD27 with a "goose-neck" style fixture in the main cabin and kept the old one in a "junque-box" for possible later use. (Don't let your wife intimidate you about keeping valuable items! -- Mine has put up with them for almost 34 years!) I replaced the 1981 version with the 1980 version (identical) and all is fine.
Also, I have had some problems with the bulbs' solder "flowing" on the base of the bulbs from years of constant pressure under installation. Easiest fix is to buy a hasl-dozen new bulbs.
What Dave Stump said is true of many exterior lamp connections, but I haven't found any "interior" or cabin lamps using the grease. If they did put any of the grease in the lamps, as Dave cites, you may have some troubles there. Make sure you are using the proper dual contact base bulbs too.
On the CD27 I installed a light fixture in the head which used a similar dual-contact bulb, but had a "shade" on the fixture which spread the light around the area (for reading, etc.) better than the original fixture and it had a pull-chain switch. The shade was made out of plastic of some type, but the CD27 didn't have the shower, so it didn't matter what material it was made out of.
It is important to be able to find the head, so make sure you work on this pronto! The First Mate, surely, won't let you forget!
Best Regards,
Lyn Heiges
lheiges@compuserve.com
Our CD28 (1981 # 307) is also old enough to vote!
The problem could be the switch on the fixture which no longer functions. I had this happen to the portside V-berth fixture on our CD28. I had replaced a similar fixture on my previous CD27 with a "goose-neck" style fixture in the main cabin and kept the old one in a "junque-box" for possible later use. (Don't let your wife intimidate you about keeping valuable items! -- Mine has put up with them for almost 34 years!) I replaced the 1981 version with the 1980 version (identical) and all is fine.
Also, I have had some problems with the bulbs' solder "flowing" on the base of the bulbs from years of constant pressure under installation. Easiest fix is to buy a hasl-dozen new bulbs.
What Dave Stump said is true of many exterior lamp connections, but I haven't found any "interior" or cabin lamps using the grease. If they did put any of the grease in the lamps, as Dave cites, you may have some troubles there. Make sure you are using the proper dual contact base bulbs too.
On the CD27 I installed a light fixture in the head which used a similar dual-contact bulb, but had a "shade" on the fixture which spread the light around the area (for reading, etc.) better than the original fixture and it had a pull-chain switch. The shade was made out of plastic of some type, but the CD27 didn't have the shower, so it didn't matter what material it was made out of.
It is important to be able to find the head, so make sure you work on this pronto! The First Mate, surely, won't let you forget!
Best Regards,
Lyn Heiges
Mike Everett wrote: Although I'm no expert on electricity, when Dr. Pepper's first mate told me that the cabin light in the head wasn't working I thought that changing the bulb would be a quick fix. But no dice.
Dr. Pepper is a Cape Dory 28 that's old enough to vote.
After an investigation with a multi-tester, here are the symptoms.
All the other cabin lights work.
The light fixture in question works when hooked up to any other twelve-volt source.
The wires leading to the fixture show thirteen volts on the multi-tester.
But these wires connected to the this fixture do not work.
My only theory is that the wires show sufficient charge, but are corroded to the point that they can't carry enough current to power the bulb. Is this possible? Any ideas will be appreciated.
lheiges@compuserve.com
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Larry DeMers
Re: s/v Dr. Pepper's 12 volt mystery
I ran into something like this on the galley light over the stove. Turned out to be a loose connection inside of those damnable butt splices that they used. Those things should be outlawed!! There is only a point contact with the wire, and if this is a timid connection..ie: not crimped to the right pressure, then the connection will corrode over time.
Ok, what I suspect is that left alone, that connection at the butt splice is bad. When you pulled the screws out and lifted the light off the wood the connection got moved around til it made contact properly..or even partially.
Did you try to run the light with it dismounted from the wood? Did it work? If not, but yet you measured 12-13 v there, then yuou are right, there is a current limiting connection someplace..
I also noted that one of the switches on my breaker panel that gets very little use..as it is always turned on is the interior lights switch. I noticed that occasionally, the lights would flicker and then turn back on. I exercised that switch a few times, and cured the flickering problem. I suspect corrosion had effected the toggle switch, and operating it cleaned the corrosion off the contact area (toggle switches usually use a wiping motion when the contacts close, thus cleaning them off).
Good Luck,
Larry DeMers
s/v DeLaMer
Cape Dory 30
demers@sgi.com
Ok, what I suspect is that left alone, that connection at the butt splice is bad. When you pulled the screws out and lifted the light off the wood the connection got moved around til it made contact properly..or even partially.
Did you try to run the light with it dismounted from the wood? Did it work? If not, but yet you measured 12-13 v there, then yuou are right, there is a current limiting connection someplace..
I also noted that one of the switches on my breaker panel that gets very little use..as it is always turned on is the interior lights switch. I noticed that occasionally, the lights would flicker and then turn back on. I exercised that switch a few times, and cured the flickering problem. I suspect corrosion had effected the toggle switch, and operating it cleaned the corrosion off the contact area (toggle switches usually use a wiping motion when the contacts close, thus cleaning them off).
Good Luck,
Larry DeMers
s/v DeLaMer
Cape Dory 30
Mike Everett wrote: Although I'm no expert on electricity, when Dr. Pepper's first mate told me that the cabin light in the head wasn't working I thought that changing the bulb would be a quick fix. But no dice.
Dr. Pepper is a Cape Dory 28 that's old enough to vote.
After an investigation with a multi-tester, here are the symptoms.
All the other cabin lights work.
The light fixture in question works when hooked up to any other twelve-volt source.
The wires leading to the fixture show thirteen volts on the multi-tester.
But these wires connected to the this fixture do not work.
My only theory is that the wires show sufficient charge, but are corroded to the point that they can't carry enough current to power the bulb. Is this possible? Any ideas will be appreciated.
demers@sgi.com