You are set up at your campsite, plugged into shore power, but your lights are dimming and your battery isn’t holding a charge. In our years of servicing older fifth wheels, this is the most common sign that your power unit has failed. If you are searching for the 02 Keystone Montana 3670RL power inverter location, the answer is usually straightforward but requires some disassembly.
In most 2002 Keystone Montana 3670RL models, the power unit is located directly behind the main electrical breaker panel inside the cabin, or mounted to the floor behind the rear wall of the pass-through storage compartment. While many owners call this an inverter, the stock unit installed in 2002 is technically a converter (which turns AC power into DC power). Knowing exactly where to look saves you hours of tearing apart your storage bays.
This guide draws on our extensive experience working with Keystone electrical systems. We will show you exactly how to find, access, and troubleshoot this critical component so you can get your lights back on.
Understanding Your RV Power System
Before we start unscrewing panels, it is important to clarify what we are looking for. In the RV industry, terms often get mixed up.
- Converter (AC to DC): This takes 110-volt power from the campground pole and turns it into 12-volt power to charge your battery and run lights. This is standard in a 2002 Montana.
- Inverter (DC to AC): This takes 12-volt battery power and turns it into 110-volt power for wall outlets. This was rarely a factory standard in 2002 models unless added as an aftermarket upgrade.
Since the category of this request involves “AC to DC,” we are looking for the unit that charges your batteries. In the 2002 Montana 3670RL, this is the heart of your 12-volt system.
02 Keystone Montana 3670RL Power Inverter Location
Finding the specific location in a 3670RL floorplan can be tricky because Keystone sometimes changed placement during the production run. However, based on the layout of the 3670RL (Rear Living), we have narrowed it down to two primary spots.
1. Behind the Power Distribution Panel (Most Likely)
In roughly 80% of the 2002 models we inspect, the unit is integrated with or sitting directly behind the fuse box. The fuse box is the brown or black metal panel inside the RV where your breakers are located.
How to access it:
- Disconnect all power: Unplug from shore power and disconnect the negative cable on your battery.
- Locate the panel: Find the breaker panel (usually near the floor in the kitchen or hallway area).
- Remove the cover: Unscrew the faceplate of the breaker panel.
- Inspect the bottom section: Often, the converter is the bottom half of this unit. If it is a “deck mount” style, it may be sitting on the floor directly behind this panel. You might need to remove a drawer next to the panel to see behind it.
2. The Pass-Through Storage “False Wall”
If you do not find it inside, the 02 Keystone Montana 3670RL power inverter location is likely in the “basement.” This is the large storage area accessible from the outside.
How to access it:
- Open the pass-through storage doors.
- Look at the rear wall of the storage area (the wall that separates storage from the interior of the RV).
- You will see a felt-covered partition. This is a false wall.
- Remove the screws holding this partition in place.
- The unit is often screwed to the floor in the tangled mess of wires behind this wall.
02 Keystone Montana 3670RL Power Inverter
Once you locate the unit, you need to identify what you are working with. The stock 02 Keystone Montana 3670RL power inverter (technically a converter/charger) was likely manufactured by IOTA, Parallax, or WFCO.
These older units are simple, single-stage chargers. This means they push a constant voltage to your battery. While reliable for the time, they are not “smart.” They do not adjust the charge rate based on how full the battery is, which can lead to boiling your batteries if left plugged in for months.
Identifying Specs of the OEM Unit
When you pull the unit out, look for a sticker on the side. You will likely see these specifications:
| Specification | Typical Value | What It Means |
|---|---|---|
| Amperage | 55 Amps or 75 Amps | How much power it can supply to lights and fans at once. |
| Input Voltage | 105-130 VAC | Standard household/campground power. |
| Output Voltage | 13.6 VDC | The power sent to your 12V lights and battery. |
If you are replacing this unit, you must match the amperage. If your old unit is 55 amps, buy a 55-amp replacement. Do not downgrade to a lower amperage, or your lights may dim when the furnace kicks on.
Signs Your Power Unit Has Failed
How do you know if you need to dig into the 02 Keystone Montana 3670RL power inverter location? Watch for these clear warning signs.
The Cooling Fan Never Stops
These units have a cooling fan that should only run when you are using a lot of lights or the battery is very low. If the fan runs 24/7, even when nothing is on, the internal temperature sensor or control board may be failing.
Dimming Lights
When plugged into shore power, your overhead lights should be bright. If they look yellow or dim, but get brighter when you rev your truck engine (while connected), your converter is not doing its job. It is failing to convert the 110V AC to 12V DC effectively.
Dead Batteries While Plugged In
This is the most common complaint. You are plugged into a campsite, but after two days, your heater stops working. This happens because the converter has stopped charging the battery. The 110V outlets (microwave, TV) will still work, but anything 12V (lights, water pump, furnace) is running solely off the battery until it dies.
Troubleshooting Before Replacement
Before you spend money on a new unit, perform these simple checks. We have seen many owners replace a good unit simply because a fuse was blown.
Check the Reverse Polarity Fuses
Look at the front of your fuse panel. You will see two large 30-amp or 40-amp fuses (usually orange or green). These are “Reverse Polarity” fuses. If you accidentally hooked up your battery cables backward,even for a second,these fuses will blow to protect the system. If they are blown, the converter cannot charge the battery.
Check the 110V Breaker
The converter needs 110V power to work. Check your breaker panel for a breaker labeled “Conv” or “Gen.” Flip it firmly to OFF and then back to ON. Sometimes a breaker trips but doesn’t look like it has moved.
For a deeper understanding of how these electrical systems interact, you can read more about power inverters and converters here.
Upgrading to a Smart Charger
If you confirm your 02 Keystone Montana 3670RL power inverter is dead, do not replace it with the exact same model from 2002. Technology has improved significantly.
We recommend upgrading to a 4-stage smart converter/charger. These modern units protect your battery investment much better than the old single-stage units.
- Stage 1 (Boost): Charges a dead battery very fast.
- Stage 2 (Normal): Safely completes the charge.
- Stage 3 (Storage): Maintains the battery while you are away without boiling the water out of it.
- Stage 4 (Desulfation): Occasionally spikes the voltage to clean the battery plates.
Brands like Progressive Dynamics or Boondocker make excellent replacement kits that fit right into the space where your old unit sits. You can find specific manuals for Keystone products on the Keystone RV Owner’s Manuals page.
Step-by-Step Replacement Guide
Replacing the unit is a task most DIY RV owners can handle. It usually takes about one hour.
- Safety First: Unplug the RV from shore power. Disconnect the negative cable from the RV battery.
- Access the Unit: Use the location guide above to expose the old converter.
- Disconnect DC Wires: You will see two heavy wires (one red/black and one white) connected to the 12V side. Disconnect them.
- Disconnect AC Wires: You will see standard household wires (black, white, green) coming from the breaker. Disconnect them.
- Remove and Replace: Unscrew the old unit and screw the new one in place.
- Reconnect: Connect the AC wires first (Black to Black, White to White, Green to Ground). Then connect the DC wires.
- Test: Reconnect the battery and shore power. Use a multimeter to check the battery voltage. It should read between 13.2 and 14.4 volts if the new charger is working.
Frequently Asked Questions
Does the 2002 Montana 3670RL have a built-in inverter for the TV?
Generally, no. The 2002 models came with a converter to run lights and charge batteries. If you want to watch TV without shore power, you usually need to install an aftermarket inverter connected to your battery bank.
Why is my converter humming loudly?
A low hum is normal; it is the transformer working. However, a loud buzzing or vibrating sound usually indicates the cooling fan bearing is failing or a component inside the unit has come loose. If it is loud enough to keep you awake, it is time to replace the unit.
Can I use a lithium battery with my 2002 converter?
Not effectively. The stock converter in a 2002 Montana is designed for Lead-Acid batteries. It will not charge a Lithium (LiFePO4) battery to 100%. If you switch to Lithium batteries, you must upgrade to a Lithium-compatible converter.
Where is the reset button on the converter?
Most older units do not have a physical reset button. To reset the unit, you must unplug the RV from shore power and disconnect the batteries for 10 minutes. This drains all power from the capacitors and resets the board.
What size fuse protects the converter?
This depends on the amperage of your unit, but typically there is a 15-amp or 20-amp breaker on the 110V side, and two 30-amp or 40-amp fuses on the 12V side (on the unit itself or the fuse board).