Ordinarily, I probably would not devote a whole page to something like installing a tachometer in my bus, but it turned out to be more complicated than I anticipated. On a recent trip to Riverside, CA., I decided to stop at United Speedometer Service. I've read articles about them in VW magazines, and they are always highly recommended. Their web site said that they sell VDO and Stewart Warner.
My tachograph was broken when I picked up the coach. There was an blank plate on the original gauge pod, so I only had room for one gauge right now. I must have spent an hour and a half looking at speedometers and tachometers. I had no idea that between the two companies, there could be so many possible combinations. Unfortunately, they were remodeling their building and the service shop was closed for four weeks. Since they couldn't do any fitting or installation at the time, I decided to go with the tachometer. I figured that I could install it myself and the tach could function as a speedometer also. I knew that I could follow a friend on the freeway at 65 mph, and find out how many RPMs the engine turns at that speed.
I selected the Steward Warner model 82643. I made sure that I was getting a 3 1/8" diameter, 12 volt, alternator driven tachometer. I couldn't wait to stop for lunch to look at the directions.
I stopped for lunch on the way home. I couldn't wait to get the instructions out and start reading them. My excitement turned to concern, when I discovered that I would need to figure out how many pulses the alternator puts out per engine revolution. I didn't do too bad in algebra when I was in college, but it's been a while.
| ------------ | = | -------------------- | x | -------------------- |
I did a search on the Internet for companies that work on Delco Remy alternators. I sent three or four companies e-mails asking for information on my Delco Remy 50dn alternator. Jim, at Smith Auto Electric, e-mailed back all the information that I requested. Based on the information that Jim gave me, the formula looked like this:
| ------ | = | --- | x | ---- |
I set the did switches for 6.0 pulses per revolution. Then I had to run the the wires to the dash. I ran a long green wire from the relay post on the alternator up into the coach. I ran the relay wire up the left wall of the coach, to the front relay panel (next to the driver's seat). I plan on rerouting the wire, with a couple extra wires for future gauges, later. Then I ran a red 12 volt wire and a black ground wire (along with the relay wire) from the relay panel to gauge pod. I connected the wires to the gauge and and fired up the engine. The needle sprang up to 1,000 RPMs. Even though I thought that was too high, I knew that I was making progress.
Mounting the tachometer was my next problem. The gauge itself was too big to fit through the vacant hole in the factory dash. I went to a couple auto part stores, to try and locate a surface mount bracket. No luck. Nobody stocked the brackets. On the way out of the second place, it occurred to me that I might be able to mount the gauge behind the dash. The bazel of the gauge fit the impression on the back of the dash panel, and the L-shaped brackets lined up perfectly with the lip of the bazel. Other than the fact the the numbers on the face of the gauge look more modern than the other guages, it now looks like a factory install.
So, off I went to meet my friend for lunch (in the bus of course). The only problem was that according to the guage the bus was idling at about 1,000 RPMs and redlined in the neighborhood of 4,000 RPMs. Obviously, the tach wasn't programmed correctly. After lunch, I got out my Stewart Warner instructions. Figuring that the tach was about twice what it should be, I decided to change the programming to 3.00 pulses per revolution. Since the lowest setting was 4.0 pulses per revolution, it set the dip switches for that. Now the tach told me that my bus was idling at 1,800 RPMs. Next, I programmed the tach for 12.0 pulses per revolution. This time the tach told me that the engine was idling at 500 RPMs. I took my bus for a little test drive, and every time the tach hit 2,000 RPMs, the governor cut out the engine. SUCCESS!
The final task was to connect the light on the dash. I found one of the dash light wires on one of the other gauges. I carefully cut the old wire, and spliced in the dash light wire from the tach. One last test confirmed that the tach was working perfectly.
Installing the tachometer, was much more involved than I planned. Several people on the bulletin boards told me to return the Stewart Warner and buy other brands. After all was said and done, I have to say that I am pleased with the end results.