Battery
Common no-start cause. Match size, terminal layout, and cold-cranking requirements.
Generac Error Code 1300 — Low Oil Pressure Fix
What it means: The Evolution controller detected low oil pressure during generator operation. The oil pressure switch is normally-closed (grounded to engine block) when oil pressure is present. When the controller sees an open circuit from the switch, it initiates shutdown with error 1300.
This is a protective shutdown — the generator will not restart until the fault is cleared and the condition is corrected. Error 1300 can also appear on Generac generators with adequate oil if the switch or wiring is faulty.
Common Causes
| Cause | Frequency | Fix Difficulty |
|---|---|---|
| Low oil level (most common) | High | Easy |
| Failed oil pressure switch (stuck open) | Medium | Easy |
| Chafed wiring in harness | Medium | Moderate |
| Oil viscosity too thick (cold weather) | Low | Easy |
| Failed oil pump (rare) | Low | Hard |
| Evolution controller fault (rare) | Low | Hard |
Step-by-Step Fix
1. Check Oil Level
Turn off the generator and disconnect the battery ground. Remove the dipstick, wipe, reinsert, and check the level. Low oil is the most common cause. Generac recommends 5W-30 synthetic oil for most Guardian models. Fill to the F mark only — overfilling can cause aeration and false low-pressure readings.
2. Test the Oil Pressure Switch
The oil pressure switch on Generac generators is a normally-closed (NC) switch located near the oil filter base. Disconnect the single wire from the switch terminal. Using a multimeter set to ohms, measure between the switch terminal and a clean ground on the engine block:
- Engine off: Should read near 0 ohms (continuity)
- Engine running: Should read OL (open, no continuity)
If the switch shows no continuity when the engine is off, it’s failed open — replace it. Generac oil pressure switch part 0D4567 (~$20).
3. Quick Jumper Test
Unplug the wire from the oil pressure switch. Use a short jumper wire to connect the disconnected wire terminal directly to the engine block ground. Clear the error code on the controller. Start the generator. If the generator starts and runs without error 1300 returning, the oil pressure switch is faulty. Replace it.
4. Inspect Wiring Harness
If the jumper test still shows error 1300, the problem is in the wiring between the switch and the controller. Trace the oil pressure wire through the harness — it often runs near the cooling fan shroud where vibration can chafe through the insulation. Repair any chafed sections with heat-shrink butt connectors. Test continuity from the switch connector to the controller 8-pin connector.
5. Clear the Error
After repair: Press Enter on the Evolution controller, select Clear Active Alarms, confirm. Attempt a manual start. If the code does not return and oil pressure is normal, the repair is complete.
Parts That May Need Replacement
| Part | Part Number | Cost | Where to Buy |
|---|---|---|---|
| Oil pressure switch | Generac 0D4567 | $15-$25 | Generac Parts |
| Oil pressure switch (alt) | Generac 0G0086 | $20-$30 | Generac Parts |
| 5W-30 synthetic oil (1qt) | — | $8-$12 | Hardware stores |
| Wiring harness (8-pin) | Generac 0G3978 | $35-$55 | Generac dealer |
Technician Tips
Generac generator fault codes are displayed as flashing LED patterns on the controller. The red LED indicates a fault condition; green means normal operation. Code 1500 (low oil pressure) is the most common Generac fault — check oil level first, then the oil pressure switch. Generac generators have a built-in exercise cycle (every 7 days) — if the generator fails its exercise test, it logs a fault that may not trigger a warning light. Check the controller’s fault history to find these logged events.
Maintenance: Generac recommends oil changes every 100 hours of operation or annually. Skipping oil changes accelerates wear, sludge buildup, and low-oil shutdowns, so log each service interval and verify the controller maintenance timer after service.
Need Replacement Parts?
Before ordering, match the generator part to the model number, electrical rating, and failure symptom. Check current prices on Amazon - prices and availability change frequently.