By William C. Tope
Problems and their solutions were a way of life for me in my 20 years with the Custom Body Division of The Gerstenslager Co. of Wooster, Ohio. In addition to doing all of the electrical designs for about 1500 bookmobiles, speech and hearing vans, air pollution testing vans and TV production vans, I went out on at least 34 service trips for the company.
One of the most unusual trips was to repair a speech and hearing van for the Anna State Hospital in Anna, Ill.
I had a call from the project manager at Anna State just two days before and even though he was a very good electrician, he could not determine why the Ramsey 12 volt DC hoist would not operate with 12 volts present at the solenoids. The hoist in question was used to lower the on-board generator to the ground while hearing tests were in progress, to isolate the noise and vibration from the van. When the hearing tests were completed, the hoist was used to lift the generator back up to its transport position in the van.
By the time I arrived at Anna State my customer had taken the hoist apart and had it spread out on his workbench.
Step number one was to put the hoist back together and install it in the van. The Simpson 260 Meter still read 12 volts DC at the solenoids. We were back to square one. Why did the battery power not get to the hoist?
It was 30 degrees F. on the ground that December day and with a gentle breeze blowing between my legs as I traced every inch of the battery cable down through the rubber grommets, under the chassis to a terminal block and then back up into the generator compartment. Everything looked OK. I found a flashlight and went back to get a good look at that terminal block. The terminal block was made up of two brass 3/8″ insulated studs. One cable ran from one stud to the battery and a second cable ran to the solenoids in the generator compartment. What everyone thought was a copper bar connected the two studs. The bar was aluminum.
Everything was fine at the factory inspection, but the December trip from Wooster, Ohio to Anna, Ill. through ice and snow and salty roads did an electrolytic transformation on the copper to aluminum interfaces. I threw out the aluminum bar, cleaned up the cable terminals, put both cables on one stud and we were back in business.