No disassembly required when you make the EEP connection
By Sam Brown, Master Samurai Tech/Appliantology
When you need to test a component, do you always need to just resign yourself to tearing apart the appliance until you reach it? Or is that a waste of time and energy (not to mention unnecessary liability), when you could be working smarter, not harder?
Let’s say you’re working on a Samsung dryer and you want to measure the thermistor. You know the Ohm spec, so all you need to do is get your meter probes on it so you can compare. Is your next step to disassemble the machine until you can find the thermistor’s harness, unplug it, and then do your measurement?
Or is there a way that wouldn’t require you to take the machine apart and spend time rolling around on the customer’s floor? Well, let’s crack out the schematic and put our big brains to work.
Aha! That didn’t take too long to spot. See the thermistor? And see the area connected to it that I’ve circled, right where the lines connect to the main control? That’s our ticket right there. That’s showing that there’s a harness connector on the control that connects directly to both ends of the thermistor, with no other components between.
We have located what’s called electrically equivalent points, or EEPs. These are testing points that are electrically identical to physically putting your probes on the thermistor itself. Why does this matter? Because in almost every appliance, the control is one of the easiest components to access. And by doing your test from the control, you’re eliminating unnecessary disassembly, which means saved time, which means saved money.
That was an easy one. What if one of those steam valves wasn’t operating? Let’s say the one on the right, labeled 22. How would you test for that?
The unskilled tech’s way would be to take apart the dryer until you get to the valve, then do an Ohms check on the coil. Now let’s see where a real tech would test from. First, you would set the machine to energize that steam valve. Then you would put your probes at these points:
These EEPs are a little less obvious than those for the thermistor, and they are not Ohms test points. These are the test points for doing a voltage measurement — very importantly, with a loading meter or a multimeter on the LoZ function. Voltage measurements are the preferred test over Ohms whenever possible, because they’re more foolproof.
Pin 3 on connector 6 is the voltage supply to the valve. That’s where we should have a good 120 VAC coming from the control board. Pin 1 on connector 7, on the other hand, is hardwired to neutral. That’s the reference for our test. With one simple voltage measurement, we can confirm whether or not the control is sending a good 120 VAC to the valve. No extra disassembly needed.
Enterprising techs might be wondering why I chose to do my test using Con 7 pin 1 as my neutral reference instead of Con 7 pin 3, which is the neutral that’s actually used by the valve. That’s because I wanted to check for voltage to the valve with a known good neutral, and Con 7 pin 1 is hardwired to neutral.
But you’ll notice that there are two components in the neutral for the water valves — the centrifugal switch and the door switch. How would you test those without disassembly? Do we finally have to resign ourselves to taking everything apart?
Of course not. One lead is in the same place as before (Con 6 pin 3), but now we’ve shifted the one in connector 7 over to pin 3. We’ve confirmed in the previous test that we have a good voltage supply, so now we’re using that as our reference for checking neutral. And just like the last time, it’s very important that you use a loading meter for this test!
If we again read 120 VAC, we have confirmed that we have a good neutral all the way up to Con 7 pin 3, which means that both the centrifugal switch and the door switch are properly closed.
Once you’ve confirmed a good power supply, that leaves only the valve as the culprit. Now, with complete confidence, we can get the part and install it. No fumbling around, no unnecessary disassembly to reach parts for testing.
All in a day’s work for a Master Samurai Tech! Want to learn more about troubleshooting with EEPs, like a real tech? Click here to enroll today in one of our online, self-paced appliance repair training courses at Master Samurai Tech — and be sure to use your BrandSource discount coupon for 15 percent off your enrollment.
Sam Brown is “Professor of Appliance Repair Mastery” at BrandSource partner MasterSamuraiTech.com (MST), an online training academy for appliance repair personnel, and administrator of its sister tech support site, Appliantology.org. For more information, email Sam at firstname.lastname@example.org or call (603) 290-5516.