The converter turns campground or generator power, the same kind that comes out of a house outlet, into the 12 volt power your lights, water pump and fans run on, and it charges the house battery. If the battery goes flat while you are plugged in, measure the converter's 12 volt output before replacing anything.
The RV Converter: What It Does, Signs It Is Failing, Replacing It
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At a glance
- What it does: runs the RV's 12 volt circuits from shore or generator power and charges the house battery at the same time.
- First check: the converter's 12 volt output, which most makers call healthy at 13.6 V for lead-acid; a good reading points at the fuses in the battery line, not the converter.
- Replacing it: Progressive Dynamics says match the amp rating printed on the old unit's label and never fit a higher one, because the RV's wiring may overheat.
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What the converter does
While you are plugged in, the converter powers the RV's 12 volt side and charges the battery. Keystone's 2027 owner's manual adds a third job: it feeds the incoming power through the 120 volt breakers and 12 volt fuses.
Unplug, and Forest River says the converter switches the batteries in to run the 12 volt circuits. An inverter does the opposite of a converter: it makes 120 volt power out of 12 volt battery power.
How do I know it is failing?
Many signs of a dying converter are something else, so match the sign first:
- Lights that dim or flicker usually mean an overloaded converter, says Jayco, so turn off some 12 volt lights or appliances.
- The battery goes flat while the 12 volt circuits still work: Progressive Dynamics points to blown reverse battery fuses or no battery connection.
- It runs warm and shuts down, then comes back: Forest River calls warmth normal and heat shutdown a ventilation problem.
- A slight hum is normal, and so is a fan that rarely runs on Progressive Dynamics units.
Then work through the makers' checks in order. Steps 1 to 3 are owner work with a digital voltmeter; step 4 is not.
- Measure the 12 volt output. With shore power connected, read the converter's output at its front terminals with the negative battery wire loosened (Progressive Dynamics' PD9100 and PD9200 procedure), or on the battery cables disconnected at the battery (WFCO and Jayco). A healthy reading:
- Progressive Dynamics: 13.6 V, or 14.6 V on lithium models, within 0.3 V.
- WFCO: 13.6 to 14.6 V.
- Jayco: 13.6 V DC with no load.
- Output good, battery not charging? Check the fuse or breaker in the battery positive lead, the next suspect for Progressive Dynamics. WFCO says these in-line fuses sit within 18 inches of the battery, and that the most common wiring fault is a missing ground connection.
- Output zero? Check the reverse battery protection fuses on the converter or fuse board. Only battery leads connected in reverse, even for a second, blow them, so correct the hookup and replace them with the same type and rating. On WFCO and Progressive Dynamics boards, a red LED lights beside a blown 12 volt branch fuse.
- The 120 volt side. You can reset a tripped breaker feeding the converter; Progressive Dynamics says one that trips again immediately means the converter is bad. Stop there: measuring live 120 volt power or working behind the power center cover is a job for a qualified technician, as Progressive Dynamics says, or a licensed electrician.
Where is my converter?
Your converter is either a separate box or built into the power center, and your RV's own manual says which.
Jayco's 2027 towable manual describes the first layout: the converter mounted apart from the fuse and breaker panel, often under the bed platform. The second is the wall-mounted power center, where Progressive Dynamics and WFCO build the converter, the breakers and the 12 volt fuse panel into one cabinet, which Keystone calls the power center/converter.
Charging stages and voltages
A converter does not hold one voltage: it steps between a charge stage, a normal running voltage and a lower storage voltage, and each maker times those stages its own way.
| Converter | Normal | Charge stage | Storage |
|---|---|---|---|
| Progressive Dynamics PD9200, 12 V, lead-acid | 13.6 V | 14.4 V boost | 13.2 V after 30 hours with no significant battery use, with 14.4 V for 15 minutes every 21 hours |
| WFCO WF-8900-AD, lead-acid and AGM | 13.6 V | 14.4 V until current falls to about five amps or four hours pass | 13.2 V after 48 hours of continuous AC power |
| Jayco 2027 towable manual, converter as fitted | 13.6 V absorption | Bulk only below 50 percent charge, at voltages under 13.2 V | 13.2 V float after about 44 hours of reduced load |
Sources: the PD9100/9200 guide, the WFCO WF-8900-AD manual and the Jayco 2027 towable manual.
Those voltages explain many complaints that a converter is not charging. WFCO says 13.6 V at the batteries still charges lead-acid, only slowly, and a lithium battery at that voltage is usually full already. Output also drops on purpose under loads above the converter's rating.
Tip: Voltage decides charge time more than converter size does. In a Progressive Dynamics test, a 55 amp converter took a fully discharged 125 Ah battery to 90 percent. That took about 3 hours at 14.4 V, but 40 hours at 13.6 V.
Does lithium change the converter?
Lithium changes the charging profile, not the amp rating. Keystone warns that a power center without lithium support charges a lithium battery to only about 80 percent; the fix is a dip switch, an auto-detect feature or an aftermarket converter charger.
What the makers say:
- WFCO's Auto-Detect models switch to lithium at 14.6 V on their own, with a blue LED instead of green. The battery has to be low enough to start a charge cycle first.
- Progressive Dynamics' PD9300 has selectable profiles, with 14.4 V for lithium. The PD9100L and PD4000 LI setting charge at 14.6 V, and lithium-only units must never go on lead-acid batteries.
- A PD9200 is not directly lithium compatible, but its Charge Wizard pendant gives 14.4 V for 4 hours, which Progressive Dynamics recommends once a month for lithium.
- Battle Born wants every charging source set to 14.2 to 14.6 V bulk and absorption, with equalization and temperature compensation disabled.
Sizing a replacement
The amp rating is in the model number, and the makers disagree on whether to go bigger. Progressive Dynamics says the last two digits of a PD9100 or PD9200 part number are its maximum charging current, and WFCO numbers the same way, so a WF-8935 is 35 amps.
Progressive Dynamics' FAQ says never install a higher amp rating than the original, because the wiring may overheat and cause damage or a fire. WFCO suggests a larger converter for bigger battery banks, since a 55 amp unit charges faster than a 35 amp one, but with heavier wire fitted at the same time.
The converter is also a load on your shore power connection: WFCO rates its WF-8975 at up to 15 amps of AC input.
Tip: Progressive Dynamics power centers take replaceable converter sections, so a failed unit can often be swapped without replacing the whole panel. Fitting one, and any rewiring a larger unit needs, is work on the 120 volt side: Jayco states that service and modification of the electrical system is for qualified electrical technicians only.
Common questions
What does an RV converter do?
It turns shore or generator power into the 12 volt power the lights, pump, fans and furnace board use. Progressive Dynamics and WFCO both note it runs those circuits even with no battery connected, though then there is no 12 volt power once shore power is gone.
How do I check if my RV converter is working?
You need a digital voltmeter set to the 20 volt DC range, which Progressive Dynamics calls essential for its guides. On a new RV in its first warranty year, call the coach manufacturer instead; Progressive Dynamics says a converter more than two years old is replaced rather than repaired.
How big of a converter do I need for my RV?
Go by the DC amp rating on the label of the unit you are replacing; Progressive Dynamics lists typical ratings from 30 to 80 amps. For bank size, WFCO says a WF-8725-AD will charge a 400 Ah bank, but recommends larger wire and converter sizes for faster charging from a generator.
Where is my RV converter located?
The model label tells you what you have: Progressive Dynamics prints it on top of deck-mount converters and behind the door on power centers, WFCO on the front panel next to the breakers. If it is hard to read in a tight space, Progressive Dynamics suggests photographing it with a phone, because the model number is what a replacement is ordered against.