Ruud UGPH-07EAMGR Error Code 4 Blinks (2-sec pause): Pressure Switch Shorted
What Does Code 4 Blinks (2-sec pause) Mean?
A 4-blink code on the Ruud UGPH-07EAMGR means the pressure switch contacts are remaining in the closed position when they should be open. The pressure switch is a safety device that monitors exhaust venting — it should only close when the inducer motor creates sufficient draft. When it stays closed at the wrong time, the control board cannot confirm that the venting system is working correctly.
The most common cause is a faulty pressure switch with stuck internal contacts. Over time, the diaphragm inside the switch can become stuck or the contacts can weld together, keeping the switch permanently closed. Less commonly, water or moisture accumulation in the pressure switch or its hoses can hold the contacts closed, and shorted wiring between the switch and the control board can mimic a stuck switch.
Do not attempt to bypass or jumper the pressure switch, as it is a critical safety device designed to prevent carbon monoxide exposure. A qualified HVAC technician needs to test the pressure switch, inspect the hose connections, and replace the switch if its contacts are stuck.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Stuck pressure switch contacts | Most common | ✗ Call a pro → |
| Shorted wiring to pressure switch | Uncommon | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- When this code appears — pressure switch replacement requires professional diagnosis to rule out wiring issues and ensure safe operation
✓ Verified against manufacturer service manual — March 2026