Hi everyone, I'm pretty new to RVs and could really use some guidance here. I've got a '96 Allegro Bus with what I think is called the HWH 610 leveling system. We were out camping last weekend and I started the leveling process, but someone suggested I move forward a bit for better slide clearance. So I turned off the leveling system, moved the coach forward maybe 10 feet, then tried to level again. That's when everything went wrong - now it just keeps bleeding air constantly and the pump motor won't even try to start. I've tried pressing the individual leg buttons but nothing happens except more air loss. Back home I've been doing some basic testing (please be patient with my limited knowledge). The solenoids all seem to click when I press buttons, and I've checked every fuse I can find. I suspected the pump relay since I wasn't getting any output, so I replaced it, but same problem. I'm getting confused about the wiring - should the small terminals on the pump relay get voltage or ground signal? Right now I'm seeing ground on both small posts. I also replaced all three batteries just to eliminate that possibility. I'm really puzzled how this went from working perfectly to completely dead in just 20 seconds. Any ideas what I should check next?
This sounds like a classic electrical control issue with your HWH system, likely involving the pump relay circuit or controller. The continuous air dump suggests the system is trying to level but the hydraulic pump isn't receiving power to maintain pressure.
What you're describing is a fairly common issue with HWH leveling systems, especially on older coaches. The fact that it worked perfectly then suddenly failed suggests an electrical control problem rather than a mechanical failure. The continuous air bleeding is actually the system trying to do its job - the controller is commanding the legs to extend or retract, but without hydraulic pressure from the pump, air just escapes through the leveling valves.
You're on the right track focusing on the pump relay, but there's more to check in that circuit. The pump relay should receive a ground signal on one coil terminal and constant 12V power on the other when the system calls for pump operation. If you're seeing ground on both small terminals, that indicates either a wiring problem or a controller issue.
First, verify you have 12V power reaching one side of the relay coil when the ignition is on. The relay should have constant power available, then receive a ground signal from the HWH controller to activate. Many owners report finding corroded connections at the relay socket or damaged wiring in this circuit, particularly on coaches that have seen significant road vibration over the years.
HWH controllers can develop internal faults that prevent proper pump relay operation. A quick test is to manually ground the relay coil terminal that should receive the ground signal from the controller. If the pump runs when you provide a direct ground, the controller isn't sending the proper signal.
Check the main power connections to the HWH controller itself. These systems typically require both chassis 12V power and house battery power to operate correctly - verify requirements for your specific system. Even with new batteries, poor connections can cause control issues. Understanding your RV's electrical system becomes crucial when diagnosing these interconnected problems.
Start by checking voltage at the pump relay socket with the system turned on and calling for leveling. SAFETY: Ensure shore power is disconnected and use proper electrical testing equipment with insulated probes. You should see 12V on one coil terminal and ground on the other when the controller activates the pump. If voltage is present but no ground signal appears, the controller likely needs replacement or has internal wiring damage.
Next, inspect all connections in the main junction box, typically located in a basement compartment. These connections handle significant current loads and commonly develop resistance due to corrosion or loose terminals. Clean all connections with electrical contact cleaner and ensure tight assembly.
Many owners find success bypassing the original pump relay temporarily with a new relay and jumper wires to isolate whether the problem is in the relay circuit or elsewhere in the system. This diagnostic approach helps narrow down the failure point without replacing expensive components unnecessarily.
HWH controllers on mid-90s coaches commonly develop internal failures, particularly in the pump control circuits. The sudden nature of your failure - working perfectly then completely dead - points toward an electronic component failure rather than gradual deterioration.
Controller replacement involves careful attention to wire routing and connections, as these units integrate with multiple systems including slide-out controls on many coaches. Before condemning the controller, verify all power and ground connections are solid and providing proper voltage.
Some owners report intermittent operation that eventually leads to complete failure, suggesting internal relay contacts or circuit board deterioration. If voltage and ground signals check out at the pump relay but the relay won't activate, suspect controller internal failure.
Once you get the system working again, regular maintenance prevents many electrical failures. Clean and inspect all connections annually, particularly ground points that see moisture exposure. Keep relay contacts clean and replace relays preventively every few years as they're inexpensive insurance against roadside failures.
Document your wiring and relay locations for future troubleshooting. Many owners create a simple diagram showing relay positions and wire colors, which proves invaluable when problems arise in remote locations.
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