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Old 06-24-2014, 09:28 PM   #1
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HVAC Melted connector

So my blower stopped working on my heater....pulled the controls off and found it to be melted. (see attached) Is this a common known issue? What's the best fix, just to replace it both the switch and the plug? Is the root cause the fan is old and drawing more amps?
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Old 06-25-2014, 09:06 AM   #2
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After doing more research.... Looks like this is a common problem. Time to replace the blower and switch.

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Old 06-25-2014, 09:40 AM   #3
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Optionally you can do what I just did and go to the store and buy (3) 15 cent/piece electrical female connectors (the small ones- take in that little burnt switch piece and match the size up)

Cut the 3 wires (make sure you note which wire goes where) crimp the connectors on and plug them back in one at a time...fixed my fan for 45 cents lol.
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Old 06-25-2014, 10:41 AM   #4
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Originally Posted by Letzride View Post
Optionally you can do what I just did and go to the store and buy (3) 15 cent/piece electrical female connectors (the small ones- take in that little burnt switch piece and match the size up)

Cut the 3 wires (make sure you note which wire goes where) crimp the connectors on and plug them back in one at a time...fixed my fan for 45 cents lol.
I will do that...but my fear is that reason it melted is that the blower is drawing too many amps. So plan to replace the vacuum switch and the blower along with the 3 female connectors and hopefully it will last another 15 years.
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Old 06-25-2014, 02:13 PM   #5
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I've replaced a melted fan speed switch on both TJ's I've owned. I read the wires are not big enough to handle the juice on high setting. The part number for the fan speed switch is SW2252, I got both at Autozone with a lifetime warranty. Hope this helps.
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Old 06-25-2014, 02:42 PM   #6
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The fan motor drawing too many amps is an old wives tale as is the undersize wires. Electrical engineers actually do engineer electrical circuits so that the fuse in the circuit is the weak link if everything in the circuit is in good condition. The fuse will pass less current before blowing than the capacity of the wire being used, and the connectors used.

The problem with the connector melting is simply a poor connection at the connector resulting from either loose or corroded connectors. With a poor connection there, it in fact becomes a second fuse with a smaller value than the circuit fuse and as it starts to burn through, produces heat melting the plastic connector.

Bottom line is if the fan motor was actually drawing excess amps and the rest of the circuit was in good condition, it would blow the fuse before melting connectors.
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Old 06-25-2014, 10:56 PM   #7
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The fan motor drawing too many amps is an old wives tale as is the undersize wires. Electrical engineers actually do engineer electrical circuits so that the fuse in the circuit is the weak link if everything in the circuit is in good condition. The fuse will pass less current before blowing than the capacity of the wire being used, and the connectors used.

The problem with the connector melting is simply a poor connection at the connector resulting from either loose or corroded connectors. With a poor connection there, it in fact becomes a second fuse with a smaller value than the circuit fuse and as it starts to burn through, produces heat melting the plastic connector.

Bottom line is if the fan motor was actually drawing excess amps and the rest of the circuit was in good condition, it would blow the fuse before melting connectors.
So do you recommend just replacing the female connectors like Letzride suggests? What is the risk for fire? That is probably the biggest scare/worry.
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Old 06-25-2014, 11:04 PM   #8
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The fan motor drawing too many amps is an old wives tale as is the undersize wires. Electrical engineers actually do engineer electrical circuits so that the fuse in the circuit is the weak link if everything in the circuit is in good condition. The fuse will pass less current before blowing than the capacity of the wire being used, and the connectors used.

The problem with the connector melting is simply a poor connection at the connector resulting from either loose or corroded connectors. With a poor connection there, it in fact becomes a second fuse with a smaller value than the circuit fuse and as it starts to burn through, produces heat melting the plastic connector.

Bottom line is if the fan motor was actually drawing excess amps and the rest of the circuit was in good condition, it would blow the fuse before melting connectors.
This ^^ lol... Part of the other reason is because sometimes people opt to throw higher rated fuses in those spots to...like I found a 15 amp in mine
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Old 06-25-2014, 11:07 PM   #9
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So do you recommend just replacing the female connectors like Letzride suggests? What is the risk for fire? That is probably the biggest scare/worry.
should be no more risk than the factory switch...The reason the switch no longer works is because it isn't getting power anymore because the wires/connection is burnt. If you put new connectors on, all you are doing is cleaning up the area. As long as you have the proper fuse in place, it should not catch fire.

Think about it, all you have done is repaired the wire that was burnt.... I personally put a piece of electrical tape around my middle connector so that I didn't have to worry about the snug fit possibly moving and shorting against the other wires
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Old 06-25-2014, 11:19 PM   #10
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It Is true that a good HVAC fan motor doesn't draw too many amps and won't melt wiring or connectors. The problem is that when the fan motor starts to go bad, it starts drawing too much current from its shorted windings. A good fan motor is supposed to draw something like 14-15 amps on its highest fan speed setting. They can start pulling 25 amps or more once they go bad which is what starts melting things. Which is what happened to the wiring and connector on my '97 TJ when its HVAC fan motor went bad. The fan motor being able to draw too much current for its surrounding circuitry is no old wive's tale.
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Old 06-26-2014, 09:00 AM   #11
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It Is true that a good HVAC fan motor doesn't draw too many amps and won't melt wiring or connectors. The problem is that when the fan motor starts to go bad, it starts drawing too much current from its shorted windings. A good fan motor is supposed to draw something like 14-15 amps on its highest fan speed setting. They can start pulling 25 amps or more once they go bad which is what starts melting things. Which is what happened to the wiring and connector on my '97 TJ when its HVAC fan motor went bad. The fan motor being able to draw too much current for its surrounding circuitry is no old wive's tale.
I think you misunderstood me Jerry. What I am saying is that the circuit (in this case) a 40 amp circuit which means that the fuse is 40 amps, and the wiring and connectors (if in good repair...and clean and tight) are rated at more than 40 amps. So even when the motor gets old and tired and starts drawing 25 amps, it won't burn/overheat the wires or connectors unless there is a connection issue...loose wire etc. and if the motor was to draw more than the circuit rating, the fuse should blow before the circuit wiring burns up.
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Old 06-26-2014, 09:06 AM   #12
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For ****s and giggles, what would get hot and possibly melt if there was an otherwise good circuit whose connector suddenly corroded and became resistive?

A) Both the wiring and the connector?
B) Just the connector?
C) Just the wiring?
D) The entire circuit including the switch and resistor pack?

Remember to apply Ohm's law to all this.
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Old 06-26-2014, 09:40 AM   #13
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Also, If you increase the resistance in a circuit with a bad connector, what happens to the current flow through that circuit? Does it increase or decrease? Again, keep Ohm's Law in mind here.
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Old 06-26-2014, 10:44 AM   #14
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I only lasted a 1/2 a Semester in Electrical Engineering and realized I was better suited for Computer Science. But applying lots of Voltage/Amps to Resistors to make them smoke was cool.




But has it been proven that the switch melts from the heat from resistance or is it the heat from arc'ing?
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Old 08-17-2014, 08:56 PM   #15
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So do you recommend just replacing the female connectors like Letzride suggests? What is the risk for fire? That is probably the biggest scare/worry.
So what did you end up doing? My fan just stopped working because the plug melted just like yours
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Old 08-17-2014, 09:18 PM   #16
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take them out, ditch the connector, and put new connectors on and keep them in the same order...
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Old 08-17-2014, 10:35 PM   #17
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So it happened because of corrosion and poor contact? And new connectors will fix the problem? Just trying to sort it all out in my head
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Old 08-18-2014, 10:14 PM   #18
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When you replace it, make sure to use dielectric grease on the connection, it will help get rid of any heat...
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Old 08-19-2014, 08:37 AM   #19
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When you replace it, make sure to use dielectric grease on the connection, it will help get rid of any heat...
If you use dielectric grease, make sure you only use it after the connections are made. Do not put it on the terminals before plugging them on. Dielectric grease is an insulator, not a conductor. It is made to keep oxygen from getting to a connection.
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Old 08-19-2014, 11:43 AM   #20
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Same thing happened on my 2002 Grand Cherokee. Jeep's fix was to replace the melted blower motor resistor and install a new wire harness with updated connectors. The problem was with too much resistance in the connector which generated heat. Very scary since there are numerous stories of GC's starting on fire related to this issue.
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Old 08-19-2014, 03:28 PM   #21
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So what did you end up doing? My fan just stopped working because the plug melted just like yours
I did just replace the OEM melted connector with crimp on female connectors. Seems to work fine, but it has been so hot out that I have not been able to run my blower on high for extended periods.

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