Blue Chips
Forum Supporter
- Messages
- 751
- Location
- Maine, USA
This was a simple idea, which, as usual, I made more complicated.
The battery indicator light bulb (idiot light) on my New Holland GT18 garden tractor was missing, and after installing a bulb, I found that the battery light was always on, even though the charging system checked out perfectly. That led me to a faulty battery light module, which is probably why a previous owner removed the bulb. Here's the culprit:
A new OEM battery light module was WAY too expensive. I saw some generic aftermarket modules for less cash, but instead of staying with the old idiot-light system, I decided to have some fun and replace it with a voltmeter. The voltmeter would have to fit in the little trapezoidal cavity that was the former home of the battery light, so I poked around a bit and found some miniature, low-cost, self-powered, two-wire voltmeters.
The ones that were already potted (above right) wouldn't fit unless I modified the dashboard, due to the wires coming out of the side, so I opted to use one of the others and pot it myself. One of those would easily fit into the battery light cavity if I clipped the two mounting ears off the circuit board. I did a preliminary potting step by squishing a dab of non-corrosive, non-conductive silicone onto the little circuit board, being careful to fill any voids. I didn't think it was worth setting up a vacuum-impregnating rig.
The next step would be to make a cast around the voltmeter in the battery light cavity, using some two-part urethane rubber casting resin that had been sitting around on a shelf for a while, and I wanted to start using it before it went past its use-by date.
However, before making a cast around the voltmeter, I decided to make a test casting. I applied a coat of PVA mold release on the inside of the battery light cavity.
I then mixed the urethane rubber resin and poured it in. After it cured, the test piece came out fairly easily and looked good.
I recoated the inside of the cavity with mold release, sealed the hole around the wires, suspended the voltmeter in place with some tape, and poured the resin.
I removed the casting from the cavity and washed off the mold release. I was pretty happy with the way it turned out.
I removed the old red-and-black battery icon from the dashboard decal by glass bead blasting, a bit of acetone, and a Q-tip. I tried blasting a test piece first, and was pleased that it didn't warp the plastic, which is almost paper thin.
I painted the newly-cleared area black, cut out a small rectangle to match the voltmeter, and attached a small piece of clear plastic sheet behind the cutout. The reason for the cutout is that the decal sheet has some significant surface texture on the front surface (NOT from the bead blasting) that produced a fuzzy/halo effect around the numbers, and the cutout eliminated that problem.
I then mounted the light assembly and decal sheet on the tractor and installed the dashboard 'lens' over the whole thing.
The wiring was easy, as it only involved rerouting the wires that were previously connected to the old battery light module. Just some cuts, crimps, heat shrink, and a couple of cable ties.
It works great and allows me to check the voltage at a glance. When I turned on the ignition without starting the engine, it read 12.3 volts, which was accurate and in the proper voltage range. Here you see it with the engine running and charging, and it's showing what I consider to be within the proper charging voltage range.
The battery indicator light bulb (idiot light) on my New Holland GT18 garden tractor was missing, and after installing a bulb, I found that the battery light was always on, even though the charging system checked out perfectly. That led me to a faulty battery light module, which is probably why a previous owner removed the bulb. Here's the culprit:
A new OEM battery light module was WAY too expensive. I saw some generic aftermarket modules for less cash, but instead of staying with the old idiot-light system, I decided to have some fun and replace it with a voltmeter. The voltmeter would have to fit in the little trapezoidal cavity that was the former home of the battery light, so I poked around a bit and found some miniature, low-cost, self-powered, two-wire voltmeters.
The ones that were already potted (above right) wouldn't fit unless I modified the dashboard, due to the wires coming out of the side, so I opted to use one of the others and pot it myself. One of those would easily fit into the battery light cavity if I clipped the two mounting ears off the circuit board. I did a preliminary potting step by squishing a dab of non-corrosive, non-conductive silicone onto the little circuit board, being careful to fill any voids. I didn't think it was worth setting up a vacuum-impregnating rig.
The next step would be to make a cast around the voltmeter in the battery light cavity, using some two-part urethane rubber casting resin that had been sitting around on a shelf for a while, and I wanted to start using it before it went past its use-by date.
However, before making a cast around the voltmeter, I decided to make a test casting. I applied a coat of PVA mold release on the inside of the battery light cavity.
I then mixed the urethane rubber resin and poured it in. After it cured, the test piece came out fairly easily and looked good.
I recoated the inside of the cavity with mold release, sealed the hole around the wires, suspended the voltmeter in place with some tape, and poured the resin.
I removed the casting from the cavity and washed off the mold release. I was pretty happy with the way it turned out.
I removed the old red-and-black battery icon from the dashboard decal by glass bead blasting, a bit of acetone, and a Q-tip. I tried blasting a test piece first, and was pleased that it didn't warp the plastic, which is almost paper thin.
I painted the newly-cleared area black, cut out a small rectangle to match the voltmeter, and attached a small piece of clear plastic sheet behind the cutout. The reason for the cutout is that the decal sheet has some significant surface texture on the front surface (NOT from the bead blasting) that produced a fuzzy/halo effect around the numbers, and the cutout eliminated that problem.
I then mounted the light assembly and decal sheet on the tractor and installed the dashboard 'lens' over the whole thing.
The wiring was easy, as it only involved rerouting the wires that were previously connected to the old battery light module. Just some cuts, crimps, heat shrink, and a couple of cable ties.
It works great and allows me to check the voltage at a glance. When I turned on the ignition without starting the engine, it read 12.3 volts, which was accurate and in the proper voltage range. Here you see it with the engine running and charging, and it's showing what I consider to be within the proper charging voltage range.
