Generac Generator FAQ: Starters, RPM Sensors, Spark Plugs & More – A Quality Inspector’s Take

Quick Answers to the Generac Generator Questions You Actually Ask

I’ve been reviewing Generac generators for over four years – roughly 200 units a year, from the 6kW standby up to the 38kW commercial models. In that time I’ve seen the same questions pop up again and again, and I’ve made my share of mistakes too. So here’s a no‑fluff FAQ covering the stuff that actually matters. No lectures, just what I’ve learned the hard way.

1. Where is the RPM sensor located on a Generac generator?

Look, I’ve had this conversation more times than I’d like. The RPM sensor (sometimes called the speed sensor) is usually mounted on the top of the engine housing, right near the flywheel. On most Generac air‑cooled models (e.g., 10‑22 kW), it’s a small black plug with two wires – you’ll find it on the valve cover side, about 2 inches from the oil fill cap. I once spent an hour hunting for it on a 26kW unit because I assumed it would be on the opposite side (ugh). Here’s the thing: the exact position can shift slightly depending on the build year. On a 2024 22kW model I inspected last month, the sensor was tucked behind a bracket – not where the manual diagram showed. So always double‑check with the serial number before you start pulling things apart. Misidentifying the sensor can lead to false error codes (we rejected a batch of sensors that were installed 1 cm off spec – cost the supplier a $12,000 redo).

2. How do I choose a starter for my Generac generator?

“Starter” doesn’t mean the same thing to everyone. Are you talking about the starter motor itself, or the battery starter that cranks the engine? For the actual starter motor (the electrical component), compatibility comes down to voltage (12V for most residential units) and tooth count on the gear. Generac uses two main starter families: the E‑Series (found on 6‑14 kW) and the R‑Series (16‑38 kW). I made the mistake of ordering an R‑series starter for a 14kW unit once – the mounting holes were 3 mm off. Cost me a rushed overnight replacement ($85 extra for shipping – a classic total‑cost oversight). My advice: pull the part number off your existing starter (it’s stamped on the side) and verify it against Generac’s online parts lookup. Also, if you’re replacing a starter because of a “no crank” issue, check the RPM sensor first – I’ve seen bad sensors misdiagnosed as dead starters in about 10% of the cases I’ve reviewed.

3. How to remove a broken spark plug from a Generac generator?

Yep, this happens. Usually because someone overtightened the plug, or the plug seized from corrosion. If the porcelain is still intact and just the electrode is broken, you can try an easy‑out extractor kit (the spiral type works best). But if the ceramic is shattered and pieces fell into the cylinder – stop. I’ve seen a $6,000 engine ruined because someone cranked it after the plug broke, grinding the ceramic into the piston walls. Real talk: for a homeowner, the safest approach is to remove the cylinder head and fish out the pieces. I know that sounds extreme, but a head gasket set runs about $40, vs. a short block at $2,000. I rejected a “repair” job in Q1 2024 where a technician used a pick tool and left metal shards – that cost us a $22,000 redo and delayed a project by three weeks. So if you’re not comfortable removing the head, call a pro. And always use a torque wrench when installing the new plug – Generac calls for 18‑20 ft‑lbs on most models (spec per the service manual, not my opinion).

4. Do I need a compressed air filter for my Generac generator?

Short answer: no, unless you’re feeding compressed air into the generator (which you shouldn’t). The “compressed air filter” people often ask about is actually for air tools or spray booths – totally different system. What your Generac generator needs is an engine air filter and a fuel filter. The engine air filter (the big rectangular one, part #0E9030A on many models) keeps dust out of the intake. I’ve seen customers try to rig a compressed air filter in place – it’s the wrong shape, wrong micron rating, and can starve the engine of air. (One guy told me “but it’s cheaper!” – yeah, until you burn a valve because of lean mixture.) Stick to genuine Generac or a high‑quality aftermarket like Briggs & Stratton. Change it every 100 hours of run time, or once a year – whichever comes first. That’s not a company line; it’s what I recommend after seeing dozens of units with dirty filters that caused hard starting.

5. Can I use a Sony Cyber‑shot battery charger to charge my generator’s battery?

I get this question so often it’s almost funny. No. A Sony Cyber‑shot charger (or any camera battery charger) outputs around 4‑5V for lithium‑ion cells – not enough to charge a 12V lead‑acid or AGM battery. I’ve had customers say “I just need to top it off” – that won’t work, and it could even damage the charger. Your generator’s battery requires a proper 12V automatic charger (like the Battery Tender Junior or Generac’s own charger). Trust me, I’ve rejected warranty claims where the battery was ruined because someone tried to “trickle charge” it with a random wall wart. Spend the $30 on the right charger – it’s way cheaper than replacing a $120 battery. (And yes, this is the same total‑cost thinking I apply to everything.)

6. So should I just buy the cheapest Generac model to save money?

Here’s where the “total cost of ownership” mindset kicks in. I’ve reviewed quotes where a customer chose the 10kW over the 16kW because it was $800 cheaper. Then they added a portable A/C unit to handle the extra load, which meant buying a second generator – total outlay actually increased by $1,200. And the installation: the smaller unit required a different transfer switch, which added another $400. So the ‘cheaper’ option ended up costing more. My advice: size your generator based on your actual peak load (I use a 48‑hour load test, not the sticker rating). Also factor in maintenance intervals – the 38kW units require oil changes every 50 hours, while the 22kW can go 100 hours. Over five years, that difference adds up. If you’re a contractor needing portable power, the GP5500 might look like a bargain, but if you’ll use it 8 hours a day, the GP6500’s larger fuel tank and better oil capacity will save you refueling time and wear. That’s the kind of math I do every day, and it rarely points to the absolute cheapest sticker price.

7. How often should I have a professional tune‑up?

Annually, at a minimum. I know the manual says “every 200 hours or yearly” – but I’ve seen units that sit for 11 months then get hammered for 100 hours in a single outage. Those years are tough. A proper tune‑up includes oil change, spark plug replacement (and checking for broken plugs – see above), air filter, fuel filter, and valve lash adjustment. I also recommend a load bank test every other year to ensure the generator can handle full capacity. In our 2024 audit, we found that 18% of maintenance‑avoidant units failed within the first 30 minutes of a 2‑hour outage. That’s a $22,000 average loss for commercial facilities (I’m citing an internal study from our service division, which tracks about 500 generators). So don’t skip it. And if you’re doing it yourself, at least check the RPM sensor location and clean the contacts – that sensor is the first thing to go when corrosion builds up.

(Note: All part numbers and specs mentioned are based on my experience with mid‑range units from 2018–2024. If you’re working with an older model or a specific variant like the 38kW Protector series, things may differ – especially the RPM sensor location. Always verify with your unit’s data plate.)