Lincoln Impinger 1302 question. I replace the main fan motor because I wasn’t getting air. New motor is not working either. I have 120 vac on two legs of the connector to the motor…any ideas?

[ectofix]

Mike Berry wrote:

 

I have 120 vac on two legs of the connector to the motor…any ideas?

 

I have an idea…

 

From the voltage readings you shared here, it sounds like you did your voltage tests by putting one test lead to ground to take each of those readings.  That is NOT the proper way to use a voltmeter when troubleshooting a component’s failure.

 

WHY?  Because ground is not part of the motor’s circuit and has absolutely NO bearing on the motor’s performance.   For that reason, I’ve ALWAYS instructed (or corrected) folks by telling them to NEVER reference ground while troubleshooting for a circuit or component failure (yes…I used to teach this stuff to a classroom). 

In cars?  YES. In some AC appliances having a low voltage secondary circuit (from a transformer) using ground as COMMON?  YES! For the 240v necessary to make your oven motor RUN?  NO!

A basic rule that I tell everyone is to look for voltage the same way a component gets it.  So generally, the only time I’ll ever lay a test lead to ground is as ONE method to verify a unit is grounded or to check that a circuit’s wire is hot.  In both of those cases, it’s just for matters of SAFETY.  That’s another topic, though.

 

So you referenced ground and got 120v to both legs.  WHY?

That motor requires 240v (or thereabouts) to operate.  The 120v you were reading (while improperly referencing ground) was voltage you were getting through the one GOOD line getting to the motor.  The reason you read 120v on both legs is because one of your 120v readings was voltage THROUGH the motor and you were simply reading open circuit voltage.  SO…it was the same 120v that you were reading coming in to the OTHER leg.

 

I suspect that either one side of the main switch is bad or there’s a faulty wire connection someplace.  I can’t assist you any further on that since I’m not there to troubleshoot it.  There are ways to use a voltmeter to track down the exact cause, but that would require more lessons on meter usage…which I won’t cover here.  It’s too detailed and would require direct supervision by somebody who’s well versed in it.

[ectofix]

OH…and congratulations on being the proud owner of a spare motor!  I say that because I doubt that the original motor was bad.

[fixbear]

I have to ask,  Was the motor running and not producing the air flow,  or was it not running at all?

[miltonsappliance]

kinda hard on the answers we were all rookies at some point first of all I’m not a big fan of these units worked on a few at ruby Tuesdays inpingers in general are a pain in the buttocks first thing I would have checked is the single or 3 phase coming in to the unit  has to have the initial power to begin with not specific on motor was it blower motor or cooling fan don’t remember if cooling fan is 120 or not but blower motor is 240 if this is not turning it wont heat due to internal centrifugal switch me more specific more details is helpful I work on chilis and bjs inpingers all the time but these are gas that Lincoln is electric glad Hobart took over them ruby Tuesdays now I just fix there microwaves there yeah

[fixbear]

They are a good oven if properly maintained and cleaned.  Can’t help if users don’t follow the owners manual.  And very few do.

[guest]

To ectofix, well spoken! I have a helper who still has a bad habit of checking everything to ground. I’m going to copy your reply and put it up in the shop. Hopefully he’ll come around before I retire.

[fixbear]

It all comes down to how they are first taught electrical theory.  As Electricians are taught to first test to ground for safety potential.  In other words, What will hurt me it I touch it.  But when you go inside a machine to troubleshoot, That isn’t how one can determine the problem. Potential across a load has to be designed voltage.  Not leg voltage to a neutral or ground that can back-feed and give you a false indication of what is happening. 

 

I once came across a machine that would tickle the operator.  Showed 110 volts to a good ground.   After much hunting I found the the sub-panel never had a separate ground to it. Code change to separate ground and nuetral  bus bars in sub panels was like in the early nineties. This panel dated from the late sixties and had no separate ground, only nuetral and the EMT conduit.  Conduit was in concrete, a no no for EMT.. So over the years it had lost conductivity of ground.

[ectofix]

From the discussion here, I was inspired to post this:

TROUBLESHOOTING