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The Mice Versus the Generator

Keep your backup power reliable by keeping vermin out

Ron Wilken, CET, is the owner/operator of RGW Enterprises, a technical solutions company based in Ontario.

During a maintenance visit to one of the sites he handles, the general manager told him that the generator contractor had reported the droppings and smell of mice in the generator room. On inspection, Ron found that someone had laid four bait traps. None had been touched, so he decided more drastic steps were needed.

Ron purchased spring-type mouse traps, a different type of bait and an electronic zap-trap for the flies and other bugs present. Ron laid the traps with peanut butter and put down some of the new bait at the transmitter site.

In doing so, Ron noticed some “fluff” on one of the generator engine covers (Fig. 1). Opening it, he discovered that the vent between the engine and alternator was plugged completely with similar fluff (Fig. 2).

Fig. 1: “Fluff” on the generator engine cover was Ron’s first clue.Fig. 2: He found that the vent between the engine and alternator was clogged completely.

Ron advised the GM that the generator contractor should come and clean out the alternator because Ron had no way of knowing what might be inside. The GM contacted the company but in checking the service sheet from the previous visit, there was no check or initial against the fuel or air filter inspections. These nests were not built in a few days; the problem had been overlooked by the generator maintenance technician.

The service company could not come until the following week, so Ron decided to open up the vent and clean out what he could. At least the generator wouldn’t overheat from lack of cooling in the alternator. Wearing a mask and protective gloves, Ron used the shop vacuum and removed what he could of the nesting material. When he started the generator, he noticed very little air blew out (Fig. 3).

Fig. 3: Little air blew through the generator even after Ron had removed the nesting material.Fig. 4: Mice nesting material also had clogged the air filter housing.

He was just about to close things up when he noticed the air filter housing too was plugged with mouse nesting material (Fig. 4). Again, Ron attacked the nest with the shop vac and managed to suck out all the fluff; he evicted three mice as well. These escaped into the room and eventually made it to the field outside as fox bait.

The filter itself was damaged; the mice had eaten a softball-sized hole in the filtering element. Fortunately it didn’t appear as a hole on the inside so it was still serviceable; but it would have to be replaced. Ron located a replacement and ordered one. It is relatively simple to change this filter, involving just a screw and a clamp.

When the new filter arrived, Ron made a screen using 1/4-inch construction cloth and a large hose clamp from the local plumbing store. To protect the filter from the sharp ends of the construction cloth mesh, he wrapped the band with multiple layers of black electrical tape.

Fig. 5: The fluff battle continues.Fig. 6: More nesting material turned up in just a few short weeks. On his return a few weeks later, Ron opened the door to the generator and found two dead mice in traps he set during his visit. He removed the dead mice and reset all four traps. Ron changed the air filter with the new one, and noted that the old one had signs of a new nest being built (see Fig. 5 and 6.) There also was more fluff in the vent again.

Fig. 7: More mice after removing the end cover.Fig. 8: The nesting material removed. Ron decided to investigate further and removed the end cover of the alternator. There, he found a huge nest with yet more mice in it. This was all vacuumed out, including one mouse (Fig. 7). Fig. 8 shows the vacuumed compartment. The generator was tested and returned to service.

He was curious as to where the mice had obtained the nesting material. He discovered the mice had destroyed half of each of two boxes of transmitter air filters. He consolidated the remaining good filters and moved them into the transmitter room, making sure there were no hitch hikers! The rest were removed to the garbage.

Ron’s next step is to find out how the mice were getting into the generator room in the first place.

His experience is a good reminder to inspect all systems at your transmitter sites and to investigate anything that doesn’t look quite right. Backup equipment, such as transmitters or generators, can be ideal spaces for infestation because they are not regularly used.

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Author John Bisset has spent 46 years in the broadcasting industry and is still learning.