How to repair a Harbor Freight heat gun Part 1

How I fixed Harbor Freight Drill Master Heat gun Item number 62546.
Part 1
My disclaimer: Do not try to do any of the things I do in this video unless you are knowledgeable about working with electricity and meters. Even if you are knowledgeable and confident that you know what you are doing, you must be very careful to not shock or electrocute yourself. Working around.120 volts AC is dangerous unless you know what you are doing. Even if you feel you know your way around electricity, be extremely careful and follow good practices and procedures. Never test for continuity, resistance, diode test mode, with power going to whatever you are going to test.
I hope you read this before watching this video, because I will be the first to admit, it would have been easier and probably cheaper to just drive to my local Harbor Freight store and buy another one of these dual speed heat guns using a HF coupon and throw the old one in the local landfill.
However, instead of throwing it into the local landfill, I decided to try to fix it.
It had three problems
1. It needed a new thermal fuse
2. It has a small circuit board with Surface Mount (SMD) Diodes that were bad and needed to be replaced.
3. The circuit board itself had a broken copper trace that needed repair.
This video is in two parts.
This Part 1 shows how to unplug the tool from the wall outlet and disassemble it, then test the power cord, power switch and the thermal fuse for continuity. Repair any of these three items if they have no continuity.
Part 2 shows how I tested the motor with a variable DC power supply. You could probably use a 1.5 volt battery to do this motor test once the circuit board is removed. Or perhaps a 9 volt battery. Or something in between. If motor is good then the circuit board is probably bad, as it was in my case. The rest of the video shows how I fixed the broken copper trace and replaced the M7 diodes. Which then allowed the blower motor to run.
Part 2 link: • Part 2 Harbor Freight ...
I was able to buy 10 new thermal fuses for $6.79 on Amazon. Only needed one. www.amazon.com...
I was able to buy new SMD M7’s Diodes for $2.39 per 20 on eBay and they worked great. Only need 4 of the 20 M7 diodes. www.ebay.com/i...
I repaired the bad circuit board trace with some existing 10 strand 24 gauge wire I had on hand. Stripped a small piece and then used one of the 10 strands to create a new trace.
I already had some Liquid tape on hand to cover the new trace so it was non-conductive to the diode the new trace was to go under. And non-conductive to the two diode posts the new wire trace went close to. I also put liquid tape under the four new M7 diodes since it looked like they had something like that under all four of the old ones.
Here is the amazon link if you are interested in the liquid tape. www.amazon.com...
I did repair the heat gun, instead of throwing it into the local landfill. The things I learned while doing this project made the project worth doing.
I think you could use similar procedures to fix other heat guns, hair dryers, and various other devices that need power cords, power switches, thermal fuses, or AC to DC rectifiers.
I do not think you could just hook up 120 volts AC to this little green circuit board and expect it to convert that to the proper DC voltage. I believe the current first goes to the heating element for a reason, I believe the heating element provides a lot of needed resistance before current goes on to the small circuit board. I have NOT proven this, but I think there must be some resistance or voltage drop before the current reaches the small circuit board.
Make sure tool or devise you want to work on is unplugged from wall outlet before attempting to disassemble and or test for continuity, resistance, or diode test, A continuity test will tell you where most problems are and is a safe test as long as no power is being supplied or is stored up in something like a capacitor. My heat gun had no capacitors, so I just unplug it and tested for continuity.
Good luck and be extremely careful should you try to fix anything that runs on 120 volt AC.

[@thetruthrover]

I have three of these guns. Two of them have quit, and each time i've gone and bought a new one, since i needed it right then. The switch seems good, and i'm thinking the problem is similar to what you show in this video. I have been hesitant to throw them away, but not sure it is worth the trouble to fix them, and if the problem is in the circuit board, that is probably beyond my abilities anyway. Thanks for the video.

[@kyfakhro]

Good piece of information. "You must crimp the heating Fuse" Soldering it will burn it !

[@johntube2525]

Thanks for taking the time to comment. My heat gun is still working, but I do let it run on low heat for a while to help it cool down. I think this also helps to NOT burn the thermal fuse.

[@AllboroLCD]

My low speed stopped working, only had high speed, then i noticed some smoke coming out. then I caught your video, turns out the 1n5408 diode was cracked. Luckily enough I dont throw out broken electronics, found a PC power supply with perfectly good 1n5408 diodes : D

[@johntube2525]

Yeah! I like it! Good job! You Kept another one out of the land fill. Thanks for doing that and thanks for commenting!

[@AllboroLCD]

@@johntube2525 I keep thinking about where this stuff ends up and I just cant let myself throw electronics away to end up in a landfill or in some child labor gold harvesting farm in africa. thnx again!

[@MarkSWilliams27]

I guess I got lucky on mine and didn't blow the thermal fuse when I repaired the gun. What happened on mine was the section of the wire after where the thermal fuse outgoing end riveted to the heating coil/element section had broken. I put a new wire on that section, wrapping it around the rivet part and soldering it on the broken wire part. The fuse should have failed rather than the wire breaking. I will be mindful about letting mine run on low setting before I turn it off. I had not done that before. I didn't know about that. So thank you. Anyway, I got a new one for what, $18? Double the cost of the one I just repaired. Same exact gun except the old one read "Drill Master" and the new one reads "Warrior". Screw for screw the exact same gun. Double the money? Hmmm.

[@johntube2525]

Thanks for sharing your experience. Perhaps it will help someone else with the same problem. Also thanks for fixing yours and keeping another item out of the landfill. Now you have a backup. Thanks for watching and contributing!

[@rbarr04]

Great video. Could you explain what the purpose of the diode is around the switch? Mine is broken in two. Thanks.

[@johntube2525]

Sorry, must of missed the notification on your comment. I am not really positive, but I think when the current goes thru the diode on the trigger, it lowers the current so you have low heat and low blower. Flip the switch the other way and current goes directly to everything and not thru the diode. That was my conclusion back when I worked on mine. I could be wrong though.

[@MrSegersall]

Got this gun from a friend to do some plastic bending. The high speed doesn't work, the low speed does. I'm suspecting either the switch or the connector to the high speed is somehow damaged. Could be feasible to just bypass the switch all together for some usage, then revert it back ? Great video, very well explained

[@johntube2525]

Yes, I suspect the trigger or switch for high is bad, since it only works on low heat. See my comment below where I explain that I think the diode near the switch is what lowers the current for low heat and lower RPS on the blower motor. So if yours works on low heat then I think the diode near the trigger is working to lower the current. So I suspect the high switch, which you could check the continuity thru the switch and I suspect you will only get continuity with it on low and no continuity thru the high. But, hey I have been wrong many times in my life. Thanks for the comment and good luck

[@johntube2525]

My wife’s Hoover Wind tunnel vacuum cleaner’s on/off switch broke. Won’t turn on. No continuity through the switch. I am ordering another switch. Until that switch gets here, I told her she could use the vacuum , but it will not have an on/off switch. It will be on when she plugs it in. Only off when she unplugs it because I put a jumper wire in place of the switch. I think you are thinking of doing something similar. Good luck!

[@jeongkim9597]

Do we need a thermal switch? Isnt the point of this unit to blast out heat? Shouldnt we just connect the ends and bypass the fuse or just replace fuse with solid connector?

[@johntube2525]

My understanding for the fuse is it is rated for a specific temperature and should that temperature be exceeded there could possibly be a fire. Better to stop the flow of current to the heating element with a blown fuse than have a fire. I am no expert, but that is what I have gathered from my research. Thanks for your comment.

[@razhocarjr]

Do you think it’s possible to switch the motors to a different gun.

[@johntube2525]

Probably! Your only problem might be how to mount the motor on a different application. I tried my motor with just 3 volts and I also tried it with 12 volts. It turns faster and faster the more voltage you apply to it. With my variable DC voltage source I could do anywhere from zero to 12 volts. I do not remember measuring the voltage at the motor after I fixed mine, to see just how much voltage is actually going to the motor. I would image it is too different voltages. Gun on high heat, motor turns faster, Gun on low heat motor turns slower. I think the diode near the trigger or switch changes the voltage for the respective high and low. Hope this helps you out.

[@kola2018]

Is the wide plug connected to hot wire ? Black wire

[@johntube2525]

No! Just like I said in the video, the wider plug or prong should be the white wire or common. The narrower plug or prong should be the hot or the black wire. If you disassemble an outlet you will see the narrow opening is the brass which should be the hot side. Other wide side should be the common.

[@kola2018]

@@johntube2525 did I make a mistake. I always cut the long extension wire and connect the black wire to the wider one. Mostly use for heat gun. It works fine. Nothing wrong. But seems like most of my heat gun last only 2-3 months. Is that something I did wrong. Let me know thanks

[@johntube2525]

@@kola2018 Not sure? I guess the color of the wire doesn’t matter as long as everything else is correct. Not sure what you have done? One thing I do know about heat guns that do not have a, fan only, cool down mode. This would mean the heating element is not turned on, but the fan is turned on and is basically just blowing the air threw the gun to allow things in the gun to cool down. These guns without a cool down mode, might not last as long as those that have the cool down mode. I always run my HF heat gun on low heat for awhile and never just turn it off after using it on high heat. Running it on low heat, will help it cool down some, compared to just turning it off after running it on high. But an actual cool down mode would be better. I think that was the way I messed up mine and the reason I had to replace the thermal fuse and the diodes. I had run it on high for an extended time and then I just turned it off instead of running it on low for a while. The high heat was left in the gun as the heating element tried to cool down, but without the aid of a fan blowing, caused the components I had to replace to overheat. I hope this helps. I am not sure what else to tell you, except that the wider prong is supposed to be the common and the smaller prong is supposed to be the hot. That is also the way your electrical outlets are supposed to be wired. Hot to hot and common to common.

[@kola2018]

@@johntube2525 is the thermostat fits most heat gun ?

[@johntube2525]

@@kola2018 You can buy new thermal fuses on Amazon see the link I have in the description. I believe mine was rated at 133 degrees Celsius. I would try to replace it with one rated the same rating as whatever is written on the side of yours. Or if you cannot find an exact match, you could go slightly higher. Here again, your question is not very clear, but hope this helps.

[@bobbyhutcheson1084]

This guy is so slow you'd need to drive a stick to see if he moved any!

[@johntube2525]

LOL! I was wondering where that stick came from!😄

[@bobbyhutcheson1084]

Yea good sport,that's the way to see if river is riding or falling,drive a stake then 24 hrs look for change.Thumbs up to you and I subscribe