Baby Don’t Fear the Skid Steer

For most service shops on the automotive or heavy truck side of things, as soon as a customer asks if they can look at the air conditioning on his piece of equipment hooked onto the back of a pickup truck or on a trailer behind a dump truck, the first thought is, “I’m not touching that thing, I don’t know the first thing about air conditioning on it.” You should not fear what you do not know.

For the vast majority of small construction equipment out there today, the air conditioning system is vastly less complicated than that in virtually all of today’s cars and trucks. Now obviously we are going to talk about equipment that is easily transported around, used by landscapers, pool installers, utility service people, and small contractors. These are the small loaders, backhoes, dozers, mini-excavators, and skid steers that all seem to come with cabs, heaters, and air conditioning as standard or a factory-installed option, designed for operator comfort.

The systems on the majority of small equipment today are as simple as, or simpler than, automotive systems have ever been.

There are two basic styles of system. First there is the standard expansion valve style system with a compressor, filter-drier, expansion valve, thermostat (or thermistor), pressure switch group, and control group. The second style is the orifice tube arrangement with a compressor, sometimes a drier, orifice arrangement, accumulator (with desiccant if no drier present), thermostat (or thermistor), pressure switch group, and the control group.

You will never see a vacuum-controlled system or a POA valve arrangement. With most mini equipment, backhoe loaders and skid steers, the systems are going to be 12-volt, while in a few pieces you will see 24-volt. The only components that are different in a 24-volt system are going to be the compressor, condenser fans (if present), control relay (if present), and fan speed resistor (if present).

Also, any of the equipment using blend air doors, which are rarely seen on smaller equipment, may have mode door actuators that will be 24-volt.

So, with few exceptions even for a 24-volt system, most of the components will be available through an automotive parts supplier if you know what to look for.

“What about the tools or specialty service equipment that I’ll need?” you say. Well, if you don’t already have the basic service tools now, then you shouldn’t be servicing air conditioning in the first place, but we’ll review what you need anyway: a recovery recycling system properly rated for R-134a, a refrigerant identifier (I’m finding it a must, because of the refrigerant cocktails showing up that will potentially ruin a can of recovered refrigerant), manifold gauges with appropriate connectors, a vacuum pump, and a charging scale (if not part of your recovery and/or recovery recycler), a multimeter and/or a test light, and a thermometer.

Examining the system to diagnose what has failed is even easier than with an automotive or heavy truck system.

There are few if any automatic temperature control systems on smaller equipment, which means no computers to try to diagnose around. Basically, if there is no refrigerant in the system, then there is a leak somewhere. Find it the same way you would with any leaking system.

If there is refrigerant in the system sufficient to engage the low pressure circuit and the compressor isn’t on, check for a wiring problem or an electrical fault preventing power from getting to the clutch. This is the toughest part–tracing the circuit from start to finish and finding the fault, especially if there is a broken wire somewhere, or a short in the circuit causing a ground fault. Remember that most electrical systems will be wired in series, from the fuse panel to the mode selector switch to the pressure switch to the compressor. Some equipment is controlled on the ground side of the circuit using relays and diodes, but as with some trucks, just test for continuity (or lack of it as the case may be). Don’t forget to determine the cause of the problem, rather than just replacing the parts that have failed.

For instance, you need to figure out why a compressor failed. Was it because the belt wasn’t tight because the operator failed to tighten it? Or the spring-loaded tensioner failed, the idler pulley bearing failed, the condenser fan wasn’t working, or the condenser was plugged solid with debris?

The best example of an elusive problem that I have recently seen was on a small bulldozer that had the compound problem of a failed condenser fan (one of three fans) and a loose compressor belt. As the pressure rose, due to the lack of airflow across the condenser, the belt started to slip on the compressor pulley. On an automotive system, this would be noticed immediately by the driver because of the squealing involved, but on a bulldozer the engine noise often drowns out the squealing and it can’t be heard in the cab. By the time it was discovered, the bearing in the compressor had failed and the shaft seal was now leaking. So what could have been solved initially with a new condenser fan and tightening the compressor belt now cost a compressor, drier, condenser fan, new belt, a full system charge, and four hours of labour.

Next, where do you get the parts? Well, most system manufacturers (like the automotive side, few if any OEMs make their own a/c systems) are suppliers on the automotive and truck side, so there are a lot of common parts throughout.

Controls, switches, relays, resistors, driers, expansion valves, orifice tubes, compressors, accumulators, and hose and fitting components can all be found in most automotive supply catalogues. There are also a number of suppliers to the equipment aftermarket that can supply you with the aftermarket and OEM parts you might need. If worst comes to worst, go to the OEM dealer for the parts, but be prepared to suffer the sticker shock.

Another thing to remember is that it is in your best interests to go over the system with the owner and show him (or her) what to look for.

Review with them the importance of cleaning filters in the system. You might be surprised by how many owners and operators don’t clean filters, or even know that they are there. Let them know not to restrict return airflow to the evaporator by blocking the recirculation filters with anything from gloves and shirts to old food wrappers. Remind them that checking for airflow across the condenser and checking the compressor belt will often save them a lot of grief.

Let your customers know that it is a good idea to operate the system occasionally in the winter to keep seals and other components lubricated. And right now in the early spring, it is a good time to have them check and see if the system is still operating. If it’s not working, they can get it serviced prior to the summer, when they will need it and all of us will be busy servicing air conditioning, leaving them waiting in line.

So, don’t look at servicing a customer’s piece of equipment that is on his float as something you know nothing about. Instead, look at it as an opportunity to play with a big toy with probably the simplest air conditioning system that you will run into this summer.

And remember that you will rarely have a customer that won’t expect to pay a fair price for the service you provide him, because that piece of equipment is how he makes his living.