Lincoln 1301 continues to heat after power off

[olivero]

What controls the heating element?

[natehatfield]

I’m not sure how to answer that question. I’m guessing something is stuck causing the contactor to be always closed when the unit is plugged in.

[fixbear]

Again, read the schematic. it is hooked directly to the lines via the mercury contactor.

[olivero]

Oooooookay, well that’s not good. It’s a lot better to trouebleshoot when you have a pretty good understanding of what the machine is doing and what the components are doing.

Looking at the wiring diagram, it seems like there’s a temperature potentiometer.

R2 which it says is the relay for the heating element might be stuck closed or welded shut, you should take a look at it.

Is the “relay” what we are calling a contactor? In which case, nevermind that.

But look, according to your diagram, R2 controls the element, so if it’s staying on, somehow those 2 contacts are closed or that same circuit is being made up somewhere else unintentionally.

You can also ohm out the wires coming from the element back to L1 and L2 and try to trace it’s path back.

[natehatfield]

Sorry, i thought you were asking were the power was coming from that causing the contactor to stay energized (ie, what is stuck open).

[olivero]

Okay, not quite.

Good, so why don’t you try this; turn off the power to the unit, then ohm out from L1 and L2 to the element and trace where it’s coming from?

[olivero]

Here’s the diagram based on the serial

[fixbear]

Olivero, you notice in my linc above on the 20th page 7 that the heating is unfused and only switched by the mercury contactor. That contactor is controlled by the temp control. So there has to be a miss wire or the main switch is not opening. That would also explain the lack of control.

[fixbear]

Being the air pressure switch stops the contactor from closing, The wiring on the line to the temp controller via the main switch is not right. Somehow there is power going to the contactor without the main switch closed.

[ectofix]

@olivero was on the right track, but there’s just not enough “technician-like” communication happening here.

SO…LOOK at the schematic Olivero posted:

The power switch should be the first component to supply voltage necessary for BOTH heat contactor coil input circuits. When the power switch IS closed, it immediately supplies L1 line voltage to the heat contactor coil. When the power switch IS closed, it supplies L2 line voltage to the electronic temp control. The electronic temp control (ETC) supplies L2 line voltage to the OTHER side of the contactor coil. There are numerous safety components in this leg, but those don’t seem to be questionable.

YET – what we’re reading from YOUR description is that the heat contactor is getting input voltage for the heat contactor to operate…DESPITE an OPEN power switch!

Either one of THREE things are happening:

The brand new mercury contactor is installed upside-down. You have a bad power switch AND a bad ETC. The unit mis-wired and needs to be gone through using a wiring diagram.

After writing all of the ABOVE, I went back and looked through this thread to find that I haven’t seen a SINGLE voltage reading to indicate you’re knowledgeable on how to use one.

If you’re NOT, then I can’t help you. If you ARE, then try using the schematic.

This is a ridiculously simple heating circuit. If you’re just NOT understanding it, then do as @Coolertapt and just call a service company.

[natehatfield]

Thanks, I appreciate the help.

[ectofix]

I wrote that several hours ago and I easily get impatient.

Sorry about that….

Helping to troubleshoot by READING, then pounding away on a keyvboard is further aggravation, since I’m not THERE – looking over your shoulder and seeing what you’re seeing.

I don’t know your skill level or skill set, but with your proclaimed electronics background, I was expecting a bit more communication.

Nonetheless, whatever further help you need – don’t let me be the one to dissuade you from asking.

Furthermore, whatever you determine to be the cause, please still share it with us.

ALL of us are still capable of making mistake, so don’t hide yours. We cann learn from yours as well as ours if you share it.

[natehatfield]

Ok so here is what i know so far.

1) The original contactor was melted and stuck closed (see pic above.

2) I installed the new contactor upside down so that explains why it was staying on as well.

3) Element is wired properly.

4) Now that the contactor is installed correctly, it will not close as it should (heating element not heating) when oven is turned on.

So that leaves the ETC or the temperature potentiometer as being bad I think.

[olivero]

Lol.

I don’t think there’s anything bad on this thing just yet, do you have a meter, can you do readings? Ohms, volts, etc?

[natehatfield]

Yes.

[ectofix]

Now you’re getting somewhere.

The potentiometer can be easily tested with an anolog ohmmeter. Follow th testing steps on pg 42 of the manual.

Same for the thermocouple. However, your meter might not be able to read such low DC milli-volts. Try reading it with an ohmmeter to give you an idea of the general condition of it. It should be just a few ohms vs anything higher will prove it’s bad.

If you’re certain that the potentiometer and thermocouple are good, you probably do need a new ETC.

[natehatfield]

Unfortunately i can’t work on this anymore tonight, but I’ll give your suggestions a shot tomorrow. My multimeter will read millivolts so I should be able to trouble shoot those items. Interestingly I just looked at the ETC and it’s wired per the 200/208V schematic on the wiring diagram. My voltage measures 240v could this be causing me issues?

[ectofix]

That could be a problem.

[natehatfield]

So if I rewire per the 220/240V schematic should itsolve my issue? I guess I’ll find out tomorrow.

[fixbear]

The power switch should be the first component to supply voltage necessary for BOTH heat contactor coil input circuits.

That’s not correct on this machine. The heat contactor is un-switched and un-fused. It’s the contrlo curcuit and fans that are fused and switched off by the main switch.

[ectofix]

I AGREE…

What gets ME is that the safety train isn’t designed to intervene if there’s a failure on the primary control side.

There sould be another contactor for safety reasons.

I’ve seen this in other equipment. In FACT…one caught FIRE at our property for that very same reason. Everyone had gone home and assumed the unit was off. But…the heating element wasn’t.

[natehatfield]

Or it’s wired for 208…

[fixbear]

Nate, the only way this could happen is if the main 2 pole switch was not opening or was jumpered on the L1 leg. There by allowing the time delay to backfeed the temp control. Test the main switch.