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Gauging Equipment's Needs
December 1999/January 2000
by Scott Nesbitt

To get the most information from gauges on power equipment and vehicles, pay attention to what the gauges say and how they say it. You can ward off disasters and downtime by observing the movement of the dials that monitor the engine's electrical, oil and cooling systems.

The gauges on most larger pieces of golf course equipment give advance warning of approaching trouble and also indicate when there's serious trouble, for example, when the temp gauge soars to the top, or the oil gauge drops to zero. You can pick up warnings of impending trouble by watching how the needles move while the machine is warming up and working.

Don't rely on a machine's gauges to give you precise numerical readings. Heat and vibration knock many gauges off dead-accurate calibration. Always use shop test gauges to verify readings before ripping into the machine You might be repairing a nonexistent problem reported by a defective gauge.

For each machine in your fleet, establish a baseline to show the normal operating range of each gauge. Do this when temperatures are between 65 and 80 degrees F and with engine oil that's been "broken in" with at least a few hours of use. Make sure the cooling system is full and has a good radiator cap and that all belts are properly adjusted. Verify that the machine's drive line and attachments have no binding or excess looseness in the various working parts.

Start the machine and let it idle about five minutes while you watch the gauges. Mark the gauge face to show the needle positions at idle speed and at half-throttle. Work the machine normally for 10 to 15 minutes, and again make the needle positions. Ideally, the half-throttle and working marks should be in the same position. If the gauges have a digital display, write down the normal readings.


Whether the machine has a voltage or amperage gauge, it should hold steady during most machine operation. The only above-baseline movement should come after starting, when the alternator is recharging the battery. The needle may blip up or down when you turn on lights or an electric load, such as a clutch. If these gauges stay high or low for more than a few minutes, check out the battery, alternator and wiring harness.

Water temperature

The needle should rise slowly and smoothly to the baseline while the engine is warming up. The temperature should stay around the baseline when idling or working unless the day is extra-hot or the load extra-heavy.

If the needle stays low after warm-up and then rises a lot while working, a thermostat may be jammed partly open, allowing too much water into the radiator.

If the needle jumps above the baseline and then drops down during warm-up, a water pump belt may be loose or the pump itself may be damaged. If the pump's opening during warm-up, there's not enough water volume or pressure to get past the thermostat. The cooling fan may be running too slow because of a bad belt or a fan clutch that's not engaging properly when heated by hot air coming off the radiator.

If the needle only rises to the baseline when under load and stays below it during extended idling, the cooling system is probably plugged up inside, or the radiator is partially plugged by exterior chaff. With either problem, the engine can't shed enough heat when working hard.

Oil pressure

The needle should bounce up right after a cold start, then settle down shortly, when the oil reaches working temperature. It should stay near the baseline whenever the engine is at one-third throttle or more. At idle, it may be normal for the needle to drop all the way down. If you aren't sure, check with a good shop gauge.

There's a problem if the needle keeps dropping the longer you work the machine. This indicates the oil is getting thinner the longer the machine is used. If you see this, install a good test gauge and verify readings from the machine's gauges. You may simply have the wrong weight of oil - 10W when you should have 30W, for example - or oil that's too thin because it's been run too long. You may simply need an oil change.

First, sniff the dipstick to see if the oil is thinned out by gasoline or diesel fuel. Fuel can get into the oil from a leaking fuel pump or an overly rich carburetor or fuel injector. These are relatively easy external repairs, and there's often no serious damage if the problem is caught in time. Fuel-thinned oil can also result from worn piston rings letting fuel vapor into the crankcase, and that requires major surgery.

If the oil is fresh and hasn't been thinned by fuel, the cause of the drooping gauge could be a weak spring in the oil-pressure relief valve. This valve may be mounted in the engine block, in the oil filter or both. Many filters contain a bypass that opens when the filter is plugged, and this condition can also trigger low pressure readings. Try a new filter and fresh oil before doing surgery.

Finally, be suspicious of any gauge that flutters or bounces. The cause is often a loose wire connection rather than a real mechanical problem. Most newer machines use electrical gauges with a sending unit on the engine and the reading unit on the dashboard. Sending units are relatively inexpensive, and it's often more efficient to install a new one as the first step in troubleshooting a case where a gauge is sending erratic messages.

Scott Nesbitt is a freelance writer and former GCSAA staff member based in Lawrence, KS. Reprinted courtesy of Golf Course Management, September 1999.

Turf Line News December 1999/January 2000

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