Foretravel Motorhome Forums => Foretravel Tech Talk => Topic started by: Merle Hench on January 19, 2012, 09:48:59 am
Title: Switches on an older coach
Post by: Merle Hench on January 19, 2012, 09:48:59 am
Greetings,
Thought to pass on something I found in going through my 20 year old coach. Had some flakey light circuits, and after mucking around some came to find the problem was with the switches. After thousands of operating cycles and weather changes, the contact resistance had increased enough to cause problems.
I've thus far replaced 12 switches, and in each case, while the switch still worked, the contact resistance measured between 1.8 and 2.4 ohms. Doesn't sound like much, but when you're dealing with low power 12 volt circuits, it will result in a significant voltage drop across the switch.
FT still sells replacement switches; I found the same size and type of switch at an online electronics surplus outlet (60 cents each here --> ON-OFF ROCKER SWITCH, 20 AMP | AllElectronics.com (http://www.allelectronics.com/make-a-store/item/RS-148/ON-OFF-ROCKER-SWITCH-20-AMP/1.html) ). The new switches measured 0.05 ohms closed.
These only take a couple of minutes to change out in most cases. Something else to watch for when in there is loose terminals. Found a few that needed a light squeeze with pliers to restore a solid mechanical connection.
Have not been able to find a source for the momentary double pole switches, used for gen starts and water pump. Those I think will have to come from FT.
Steve
Title: Re: Switches on an older coach
Post by: Don & Tys on January 19, 2012, 12:17:45 pm
Thought to pass on something I found in going through my 20 year old coach. Had some flakey light circuits, and after mucking around some came to find the problem was with the switches. After thousands of operating cycles and weather changes, the contact resistance had increased enough to cause problems.
I've thus far replaced 12 switches, and in each case, while the switch still worked, the contact resistance measured between 1.8 and 2.4 ohms. Doesn't sound like much, but when you're dealing with low power 12 volt circuits, it will result in a significant voltage drop across the switch.
FT still sells replacement switches; I found the same size and type of switch at an online electronics surplus outlet (60 cents each here --> ON-OFF ROCKER SWITCH, 20 AMP | AllElectronics.com (http://www.allelectronics.com/make-a-store/item/RS-148/ON-OFF-ROCKER-SWITCH-20-AMP/1.html) ). The new switches measured 0.05 ohms closed.
These only take a couple of minutes to change out in most cases. Something else to watch for when in there is loose terminals. Found a few that needed a light squeeze with pliers to restore a solid mechanical connection.
Have not been able to find a source for the momentary double pole switches, used for gen starts and water pump. Those I think will have to come from FT.
Steve
Title: Re: Switches on an older coach
Post by: Pamela & Mike on January 19, 2012, 02:41:07 pm
Have not been able to find a source for the momentary double pole switches, used for gen starts and water pump. Those I think will have to come from FT.
Steve
Steve,
Our water pump switches we get from Digi-Key - 432-1122-ND (Manufacturer - RD221-MB-B-0-N) (http://search.digikey.com/us/en/products/RD221-MB-B-0-N/432-1122-ND/483694). Incase this link doesn't work they are Carling switches #RD221-MB-B-O-N and the Digi-Key # 421-1122-ND. Haven't had any trouble with the generator start switch so can't say if they are the same.
Pamela & Mike
Title: Re: Switches on an older coach
Post by: Merle Hench on January 19, 2012, 05:22:49 pm
Excellent! Thanks Mike. :)
Steve
Title: Re: Switches on an older coach
Post by: rbark on January 19, 2012, 06:38:00 pm