[Fritzbied]

Mistakenly posted this on the Dishwasher forum...Got a reply from Tom of Quality Appliance Services; was helpful but still have the problems described below.

My dryer motor died…I ordered a new motor…and it still does not work. I have measured about everything possible using the dryer diagram, including continuity (all switches, and fuses) and 120VAC.

The following failed:
When I checked for 120VAC at the PTS switch and Motor Relay, I expected 120VAC (reference Neutral) present at (1) One side of the PTS switch (was GOOD) and (2) One side of the Motor Relay contacts, large terminals, (was GOOD).
***The problem I have is 120VAC on both sides of the motor even when the push to start (PTS) button is not pressed.***

This seems to be telling me that my brand new shiny motor is bad. But I think the motor is good…wishful thinking…?

I was doing some continuity tests on the timer switch (T to BY – Good) then in the “Time Dry” position…I expected T to BY to open and BY to W contacts to close.

Bottom line….I need timer switch troubleshooting procedure….

Thanks in advance…
-----

Additional comment…
The most suspicious thing I am seeing right now is on the timer switch (T to W, T to BY). “W”-“BY” (should be Open) and same thing on “T”-“W.” Of course right now I think I need to start all over again.

R/Fritz

[denman]

ust a short note
***The problem I have is 120VAC on both sides of the motor even when the push to start (PTS) button is not pressed.***

If you have 120 at both sides of the motor you have 0 Volts across the motor, for the motor to run you need 120 across the motor where ground is does not matter

Sorry but I do not have a schematic for this unit

[Fritzbied]

Denman,
Thanks for the response…

What do you mean when you say…”where ground is does not matter”?

The procedure I am reading from says “120VAC (**reference Neutral**) should be present at:
One side of the PTS switch
One side of the Motor Relay contacts (large terminals)…until pressing the PTS switch, then 120VAC on both sides.

*** Silly question, where do I reference to neutral with my multimeter? My circuit drawing says “Neutral Terminal linked to cabinet.” Sounds like it is saying “chassis ground,” as in DC voltage checks…? The diagram shows Neutral connected to ground on one side of the “Door Switch”

Am I measuring AC voltage referenced to the wrong place? If I am, that would explain why this does not seem to make any sense. I think I need to pick up a good functional description book on appliances or home power systems.

Thanks in advance…R/Fritz

[denman]

OK here goes
You have 240 volts, basically this is two 120 volt supply lines at opposite phases with a center neutral (as one side goes positive the other goes negative relative to neutral). For the sake of argument lets take a specific point in time so we can read what essentially is a DC voltage. Neutral to a point on the alternating current wave reads positive 120 volts. If you now read the other side of the line, your reading will be negative 120 volts. Therefore if you read 240 volts line to line.

Your dryer motor and timer motor are 120 volt devices so only they use one side of the 240 volts. The heater coils use the 240 volts.

Now you measured from neutral to both sides of the motor and read 120V. From your description I got the impression you felt the motor should be running.
But what you should see is 0V on one side and 120V on the other. Then you would have 120V across the motor and it should run.

A motor is basically just a piece of wire so a voltage reading on one side will be seen on the other side until a connection across the supply is made. Same goes for a relay coil

I wish I had a wiring schematic for this unit but no such luck

You said you had a motor relay (is this a separate device, do not confuse it with the start motor windings in the motor) and the push to start switch, are these wired in series.
So with the start switch not pressed and using neutral as one side of the meter you should have
1. 120 volts at both sides of the relay coil
2. 120 volts at one side of the start switch
3. 0 volts at the other side of the start switch
When you push the start switch you now have 0 volts on one side of the relay and 120 volts on the other and the relay should close. This should complete the circuit to the motor and it should run. What complicates this is that you may also have a set of timer contacts in the circuit.

Also having 0 volts referenced to neutral does not tell you that you are actually connected to neutral. Unplug the the dyer, remove the 0 volt wire from the switch and check the continuity of this wire to the neural. It should be zero ohms.

Here is a quick and dirty check
1. Unplug the dryer
2. Remove the wires from the start switch and tape them together
3. Remove the contact wires from the start relay and tape them together. Be careful that you have the contact wires and not the coil wires.
4. Ensure that none of these can short to the frame
5. Plug the dryer in, if it runs then the problem is either the start switch or the relay coil. Do the below.
6. Unplug the dryer
7. Reconnect the relay contact wires
8. Plug the dryer in if it does not run, your relay is shot. If it runs your start switch is shot

If you have the dryer opened up you have to close the belt break sensing switch if you have one.

[Fritzbied]

Denman,

I attached a pdf copy of the Kenmore Series 90 Model 67902790 diagram. I don't see it here anywhere...perhaps you can see it. I also replied to the Forum email with the attachement...not sure if that was OK or not.

From your description I got the impression you felt the motor should be running.
--Comment…no….I was just echoing the procedure I used. But what you should see is 0V on one side and 120V on the other.

--Comment…This is what I expected to see without the PTS pushed. Then you would have 120V across the motor and it should run.


--Comment... I tested the timer switch (Open/Close) IAW the diagram chart for “Timed – Regular” setting indicated on the chart above the diagram. I checked them in “Time-Regular” and “Off”. . . They all worked correctly (Open/close). I also noted that the timer drive motor was turning.

--I will perform the remaining test you described soon as I can ....Thanks very much...Until then..R/Fritz

[denman]

I did not get the pdf

[Fritzbied]

Looks like the attachment size is too big to send using the forum...I can email it if you wish.

R/Fritz

[denman]

I am sorry but I do not like to show my personal email address on a public forum

When you said you checked the thermostats did you find all four of them, the parts break down shows 4. You should have three near the heater ( thermal bias (cycling) thermostat, self resetting thermal fuse and a non resetting thermal fuse. You should also have a non resetting thermal fuse on the exhaust vent.

[Fritzbied]

Danman...Yes. They all had good continuity. I still need to conduct the checks you mentioned earlier.

R/Fritz