Diagnose and Repair the McElroy120V Heater Unit: Power Cord Repair

Depending on the kind of person you are, you may find the following blog post extremely interesting, or extremely boring. Apologies in advance to those of you that fall into the latter grouping.

When I’m not busy building things in my garage, I’m usually busy building things at work. It may come as a surprise to you dear reader, but blogging twice a month is not my full-time job. Without getting into specifics, I currently work in the oil & gas sector. As you may imagine, this field of work uses quite a few specialized tools that are overpriced and hard to repair. Luckily for my company, I possess a healthy mechanical aptitude and can repair just about anything we currently equip our crews with. Today I thought I would share with you a bit of my repair process. I hope you enjoy.

Front View

In the image on the left, you see a McElroy 120V Heater unit. This is a standard tool used in the field by most gas crews installing distribution pipeline systems. This tool is used to heat fuse polyethylene pipe and fittings and can be adapted to a variety of situations. This particular unit was turned in with no paperwork so I have no idea what is wrong with it. The first step in diagnosing the problem is to plug in the unit and test the heating ability of the heater. Luckily for me, the problem readily made itself know once the heater was plugged in. A very common problem with this tool is internal wire breakage inside the cord. This usually takes place right at the base of the power cord strain relief connector. Now that I know at least one issue I will begin the process of removing the breakage in the cord. Time to take it apart!

Reverse Side Of The Mcelroy 120V Heater

To begin, we flip the heater over where we can access the six Torx screws that are holding the two halves of the handle enclosure together. Removal of these tools will require a T-15 Torx Bit With a Driver or very careful manipulation of a small flat tip screwdriver (not recommended).

Removing The Torx Screws
Internal View of the Heater

Once the two halves are free it is important to do a proper layout while all of the wires are still connected to the terminal blocks on the PCB board. The top half lifts up and folds under the bottom half of the heater. This layout prevents tension on the wiring and eliminates the possibility of damaging any of the components on the PCB board. It also gives you a very clear view of your work area. Now that the layout is done, perform a quick visual inspection before removing the power cord.

Removing Wires From The Terminal Block

The black and white wires of the power cord run directly into a 4-point terminal block on the PCB board. This makes removal of the wires extremely easy. Using a small flat tip screwdriver, turn the locking screw counterclockwise on each point you want to release. The wire simply slides away from the terminal block once the pressure is released.

Wires Are Free From Terminal Block

The green wire, known as the ground wire, is grouped into a cluster of three other ground wires and secured with a pinched, closed-end splice. Often, with enough force, the closed end splice will slide off of the wires. If it does not slide away easily then the wires can be cut. Regardless, the splice will need to be replaced with a new one once removed.

All Wires Are Now Free
The Section to Be Replaced

There are two options for making this repair. Simply replace the whole cord with a new cord, or remove the damaged section and reinstall what remains of the original cord. Since I already know where the break is at based on visual inspection (and years of experience), I will opt to make the repair. This is obviously much more cost effective and shouldn’t take much time.


Double Checking Continuity

Before committing to cutting the wire, use an OHM Meter to do a continuity check. Doing this, I was able to discover that the white wire was the only broken wire and the only problem spot was the area previously identified during the visual inspection. Time to snip it.

The Removed Section
The Replacement Power Cord Strain Relief Connector
The New Connector Installed On The Newly Shaved Wire

In the above photo, you may notice the newer connector looks a bit different. The updated connector replaced the original very recently due to this very problem I am fixing. The most common issue with this tool is internal wire breakage due to stress from mishandling. The breakage almost always occurs at the same spot just below the connector where the wire exits. The new connector is a bit longer and provides more flex hopefully preventing undue stress on the internal wire from regular use. As you can see in the image, I have already shaved away the protective coating and pre-clipped the ends of the wire. We are ready to reinstall.

20190124_104735The reinstall Is more or less the reverse order of the uninstall process. I didn’t bother with any pictures of this part of the process as it would just be me repeating myself. The main difference to remember when putting all the pieces back in place is to remember where each wire goes. If you cross the wires or leave wires exposed, you may get a nasty surprise or even set your heater on fire. Another thing to consider is the wire placement. Once the two halves of the heater are seated together you will have very little room for everything to fit. It is important to preposition all of your loose wires in a way that they will fall away from any pinch points inside of the heater. With everything back in place, all we have left to do is test this thing out.

My Cool Blue Workshop (Shout Out To My Manager For Letting Me Install Color Changing LED Lights On My Work Bench)
We use Fahrenheit in America… because of reasons. 

To test out the heater you simply plug it in and wait. The heater must be able to maintain a 500°F temperature in order to pass the test. I like to use two different touch pyrometers to be sure the heat is read accurately. A potentiometer is also built into the handle that allows me to calibrate the temperature to within 10° degrees of my target temp. Once this is complete its time to let everything cool off, package everything up, and send it back into the field where all my effort can be ignored and the tool can be destroyed all over again.

If you enjoyed this post then be sure to let me know by liking or leaving a comment. If it is received well then I may consider doing more like it. As you can Imagine, I have plenty of tools that need to be repaired and would love to share the process with you.

These Guys Are In Really Bad Shape

Thanks for your time.


6 thoughts on “Diagnose and Repair the McElroy120V Heater Unit: Power Cord Repair

    1. Completely missed your comment. I didn’t know your background was in electronics, that is awesome. I am completely self-taught but I feel pretty confident in my own ability. I agree about the feeling you get when you are able to fix things yourself. It’s wonderful!

      Liked by 1 person

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