Tip & How-To about APPROVED VENDOR Potential Relay, 35A, Pick Up 166 to 180 - 5MLY9

# How to wire and size a potential relay

To size a potential relay you must read the Start winding voltage (the BEMF)
which will be above the supplied line voltage, in this example I use 300 volts for math.
BEMF = 300 volts,
300v x ,50 = 150v minimum
300v x .80 = 240v maximum
300v x 1.20 = 360v continuous
So you want the Start capacitor to stay in the circuit to at least 150v BEMF or risk stalling, and you do not want the Star capacitor to stay in beyond 240v BEMF or risk
exploding the Start capacitor.
The 120% continuous rating is to oversize the coil in the potential relay that remains in the system to protect it .
If you have a compressor that is not running you will need to jump it with a Start capacitor(a large one) to the run capacitor for 1 second or so to bump start the compressor, then you can read the Start winding for the BEMF reading.

Posted by on

## Related Questions:

### 2005 Chrysler 300 3.5 engine will not start ? WILL JUST CLICK BUT WILL NOT START GOT \$7e8 ; \$7e9 CODE BUT NOT SUB MENUS ?

CODES \$7e8 & \$7e9 ? P0xxx example. What clicks ? starter solenoid ? Relay ? etc.... Do a starter system voltage drop test ,go to youtube an check out no crank - no start videos . Also check out voltage drop testing starting system .

Dec 31, 2015 | 2005 Chrysler 300

### My fridge starting after some time stopping and not starting it self unless switch off power supply and then on it will again in auto

AT TIMES YOU MAY HEAR THE COMPRESSOR CLICK OFF AND ON OVER AND OVER. Signs of a bad start relay or capacitor. Check with an OHMS meter for continuity (ohms) and voltage, capacitor can be checked for Microfares. ( if in series with the windings)
To check ur compressor with multi meter:
Disconnect and remove the relay and capacitor from compressor, somes located next to compressor in a casing.

You wills see 3 prongs coming out of compressor. 1 goes to ur start winding, 1 goes to ur run winding and the center goes to ur ground or COM

Place ur meter connector or prong on the start prong and the other on the ground (center prong) take note of the reading in OHMS for example 5 ohms.
Next place meter prong on run prong and the center ground prong agin. Take note of the reading in OHMS. Example 4 ohms

Next place meter prong on the start prong and the other on the run prong, now take note of the reading example 9 ohms. Now match the total of this ohms test with the total of ur two separate test. 9 ohms, if they match ur ok give or take 5 percent plus or minus. One more test to make to test of there is a short in compressor attach meter prong to ground prong and rub the other end of meter prong to metal ( scrape the metal clean of paint and test on metal surface not painted surface. If it shows continuity or ohms , u have a short in ur compressor. It should show infinity
God is so good: so this is why I give free advice so please thank him not me.

May 01, 2015 | Refrigerators

### Fan runs continuos

Compressor won't run or it is "clicking' on and off: This normally could be a bad start relay and over load for the compressor, dirty condenser coils need cleaning, condenser fan motor is not running or the compressor itself. To check the compressor properly you should test it with an amp meter, each compressor is rated in running amps  ( see model/serial tag or the sticker on the compressor )...if the compressor is drawing too much current, this may be why it is shutting off. Check the model tag for proper amp rating. Some relays will be easy to notice the broken with them, they may be burnt. Example oneexample twoexample three. Some of these relays can be removed and give them a little shake, and if they rattle around inside the relay is likely bad. Compressors can also seize and click on and off or one of the electrical windings inside the compressor could have opened up. You can use a test cord to help check the compressor and this also will help with the amp test. If the compressor checks ok and you want to install areplacement start relay. You will need to find out which winding is which. You will need an ohm meter to determine the windings. First check to see if you have windings in the compressor. Then check to see if they are grounded. If the compressor has windings and they are not grounded, you can find which winding is which. Check for grounded windings by reading from each terminal to a good ground on the cabinet. Read from the top terminal to the lower left terminal. Read from the top terminal to the lower right terminal. Read from the lower left terminal to the lower right terminal. Write down the resistance of each reading as you go. The highest reading you get will be the run and start winding of the compressor in series with each other. The other terminal left will be the common terminal. Read from the common terminal to each of the other terminals. The terminal with the lower resistance will be the run winding. The higher resistance the start winding. Using the original style relay is always preferred, but using a general replacement can "get you by" if needed.

Apr 03, 2009 | Refrigerators

##### Not finding what you are looking for?

1,946 people viewed this tip

Level 3 Expert

Level 2 Expert