Blower Switch Wiring Heating Up

[kevintblack]

Got a 23' 1974 Thompson. <br /><br />I went to start the boat a few days ago and my blower motors were dead. I've got 3 of them on the boat. It turned out to be an inline fuse casing that seems to have melted. The fuse was fine. <br /><br />I did run the blowers continuously the last time I had the boat out, and I'm guessing that's when it happened. I replaced the fuse casing and everything seems to be working, but the wires do seem to get pretty hot after the blowers have been running a few minutes. <br /><br />Any ideas? I'm a little concerned about the fact the the plastic fuse housing melted the way it did.

 

[Moody Blue]

Re: Blower Switch Wiring Heating Up

Something sounds fishy b-boy. Overheating to that degree is not normal regardless of how long you run the blowers for. Could be a couple of issues to look at. <br />1) the blowers are drawing to much current due to a bad connection or worn out motor (brushes, bearings etc). Probably only one of the three but could be more. If there is a bad connection, the voltage drops but the motors still need the same power so the current draw increases thereby creating more heat. Typically more heat worsens the connection problem and the condition deteriorates until something burns up or quits working or both. Are all three on the same fuse ? Sounds like the fuse rating is too high for the wire gauge being used. That is a dangerous condition because as you have seen, the wires and fuseholder could melt (catch fire ?) before the fuse pops.<br />2) wrong wire gauge used to hook-up the blowers. Is this factory wiring or aftermarket ? Improper wire gauge will get overly hot if more than the recommended current is being supplied through it.<br /><br />If it was my boat I wouldn't consider running it until I got this resolved. Sounds like a recipe for disaster.

 

[jlinder]

Re: Blower Switch Wiring Heating Up

RodC is right. Figure out what is going on before you go out again.<br /><br />Can you tell us<br />1. What guage wire do you have?<br />2. What is the rated current draw of the motors? (hopefully the motors are marked)<br />3. Measure the voltage with the motors running at a couple of places. First is at the batteries, second is after the switch, third is at the motors. Knowing where the voltage drops will be useful in diagnosing the problem.<br /><br />You may have a bad motor, as RodC says. You may need to disconnect them one at a time to find out which one is bad.<br /><br />Also, I would give thought to putting a fuse in line with each blower. Then if one goes bad it blows the fuse, protects you against overheating/fire, and you still have 2 blowers running.

 

[kevintblack]

Re: Blower Switch Wiring Heating Up

Thanks. I'll take a look at it today. I just found the problem, so I haven't had time to trace everthing all the way through the boat. Some of the wiring looks a little 'barn jobbed' to me. Is there a recommended gauge wire for running 3 blowers. These look like heavy duty units, and they look pretty old too. I was contemplating replacing them with newer units anyway.

 

[kevintblack]

Re: Blower Switch Wiring Heating Up

How many blowers does a boat need? My boat is just over 23' long. I have 2 blowers mounted on the transom, and 1 blower mounted mid-boat. There is flexible tubing running into the bilge from each blower. Does this sound sufficient?<br /><br />As far as wire gauge goes - is there ever a problem with using bigger gauge wire than needed? I tend to over-engineer everything. I'm guessing I'll end up rewiring this whole thing by the time I'm done, and I'd like to do it right.<br />The in-line fuses for each blower sound like the way to go. What size fuse would you recommend assuming a generic blower is being used?

 

[jlinder]

Re: Blower Switch Wiring Heating Up

The guage of wire you need is based on the current draw. There is a minimum size wire for the current you need to carry, and you need to take into account the length of the wire for voltage drop.<br /><br />A quick check of the listings shows blower motors that draw from 3 to 12 amps. As a guess, if you allow around 6 amps per motor you would have 18 amps total (just a guess, you need to get the real draw from the motors).<br /><br />For 18 amps I would not go below 12 guage for current carry capcity, and 10 guage would be preferred. <br /><br />If the run is long, you need to go to an even bigger wire to keep the voltage drop within limits. 10% voltage drop is maximum, I prefer the 3% level. <br /><br />I found a calculator on the web at http://www.nooutage.com/vdrop.htm . Keep in mind that the total wire length is the entire curcuit - from battery, to the switch, back to the motor, then to the ground.<br />If you have 20 feet of wire up to the switch, then another 20 feet back to the blowers, and another 6 feet to the battery ground, you have 46 feet total, or 23 feet for the calculator that asks for one way length.<br /><br />With my sample of 18 amp load, and 23 feet one way length, 12 guage will give you a 13.8% voltage drop which is too high. Going to 10 guage will get you 8.6% which is accpetable.<br /><br />You need to get your own current draw and lenght to find out what you need.

 

[jlinder]

Re: Blower Switch Wiring Heating Up

B-Boy,<br /><br />You can go bigger on the wire with no problem.<br /><br />As for fuse, check the motor. I would guess that if the motor draws 6 amps a 10 amp fuse should be fine. <br /><br />You need to account for the fact that on startup the fan will draw a high current momentarily.

 

[kevintblack]

Re: Blower Switch Wiring Heating Up

Thanks for the information. I guess this will be my project for this week. <br /><br />I can guaranetee the current setup is less than 10 guage, but I'm not sure what the exact guage is at this point. I think I'm going to rerun the wires just to be safe. Some of the connections that were made look a little dicey. They look pretty old and there is lots of electical tape everywhere.<br /><br />As for the motors, I'll test them after I run the new wire.<br /><br />Thanks again!

 

[jlinder]

Re: Blower Switch Wiring Heating Up

By less do you mean smaller, or bigger? In any event, it sounds like your best bet is to rewire from scratch. <br /><br />Make sure you have a good crimper, and seal the crip connection with heat shrink.<br /><br />Let us know how it goes.