42-25105-01 RELAY

Rheem/Ruud ProTech genuine OEM potential start relay used with a start capacitor to boost single-phase compressor starting torque and drop the capacitor out of the circuit once the motor is up to speed. Rheem publishes it as relay code A with a 336 V maximum continuous coil voltage and a 40-90 V drop-out range.

Specifications published by the manufacturer. Source: manufacturer documentation.

Specs

• BrandProTech (Rheem/Ruud OEM)
• TypePotential (start) relay
• Relay codeA
• Maximum continuous voltage336 V
• Drop-out voltage40-90 V
• Frequency60 Hz
• Dimensions2.70 x 2.60 x 2.40 in.

Cross-reference numbers

This part replaces the following OEM and aftermarket numbers:

• 42-25105-01
• 90370
• K8861-1013

Not sure if your number matches? Call (214) 340-9421 or bring the old part in — bench-testing is free.

What is the difference between a fan relay and a contactor?

Duty and scale. A fan relay switches a blower or an accessory at a few amps off a 24 volt pilot duty coil. A contactor switches a compressor and condenser fan and is built for that inrush and arcing. A relay is not a small contactor. Use one as a contactor and it will pit and weld shut.

How do I pick the right replacement relay?

Match four things: coil voltage, contact arrangement, contact rating and the mounting. A White-Rodgers 90-370 is a Type 184 SPDT with a 24 VAC coil around 77 ohms DC resistance. A 90-340 is a Type 91 DPDT with a 24 VAC coil around 175 ohms. They look alike and are not interchangeable. SPDT gives you one normally open and one normally closed set, DPDT gives you two of each.

How do I test one?

Ohm the coil first, because an open coil is a dead relay. Then energize the coil with 24 volts, listen for the pull-in, and ohm the normally open contacts closed and the normally closed contacts open. A relay that clicks but will not pass current has burnt contacts, and that reads as a dead blower even though the control board is fine.

Why did the relay burn up?

Usually the load, not the relay. A blower drawing high amps because the run capacitor is weak or the wheel is caked with dirt pits relay contacts quickly. Fix the load or you will be back for another relay before the season ends.