Wiring a Gall TS100 Is Straightforward If You Stop Overcomplicating It
I spent three hours last winter hunting down why my siren kept tripping the main fuse. Turned out I'd used 10 AWG wire for the power run but only fused it at 20 amps when the motor was pulling closer to 35 under load. The wire didn't fail. Everything downstream did. This isn't a novel problem, but it happens to everyone who skips reading the nameplate. The Gall TS100 is a dual-tone electromagnetic siren. Two chambers, two different frequencies, powered by a single 12V DC motor. The nameplate will tell you the exact current draw for your unit. Check it. Write it down. Your entire wiring plan depends on that single number. Here is how the wiring actually works, not how a brochure says it works.
Power feed and fusing
Run a direct positive cable from the battery to the siren motor. That means direct. Not through a fuse panel, not through a distribution block that also feeds your radio and charging system. Separate circuit. Separate fuse. Use a ANL or Class F fuse holder mounted within six inches of the battery positive terminal. The manual typically calls for a 40-amp fuse for the TS100, but confirm with your specific nameplate. I've seen units where the stall current spikes to 50 amps briefly during startup, and a 40-amp fuse will blow every time you trigger it in cold weather. If that happens to you, move to a 50-amp slow-blow and upgrade your wire to 8 AWG. No argument about it. Grounding is just as important and equally ignored. Run a dedicated ground strap from the siren mounting bracket back to the battery negative or a clean chassis point near the battery. A 4/0 welding cable lug crimped onto the siren horn body and bolted directly to the frame eliminates the voltage drop you'll otherwise get through a single self-tapping screw into painted metal.
Control wiring
The TS100 has two main terminals for motor power and typically two terminals for the siren chopper or tone control. Some later models use a solenoid-driven tone changer. Check your unit's terminal layout before buying anything. Gall changed wiring configurations between production runs without much fanfare. For a manual dash switch, use a standard automotive relay wired so the switch only handles the coil current. A 30-amp DPDT relay is common for siren applications because you sometimes want to run the siren on high and low tones independently. If you're doing that, you need a separate relay for each tone circuit and a three-position switch or two separate switches. One switch controls the motor relay. The second controls the tone chopper relay. Wire the switch side with 18 AWG minimum. That carries maybe half an amp. Don't skimp on quality though. Cheap switch contacts carbon over after two years and you're left with a siren that only works when you jiggle the dash panel.
Get the Full Details
The warning most people skip
Install a voltage monitor or at minimum a fused ignition-switched accessory line if you plan to leave this wired permanently. The TS100 motor will slowly drain a battery it isn't meant to power if a short circuit develops in the wiring harness. I found one case where the insulation on the control wire chafed through against a bracket and grounded to the frame. The relay stayed energized because the switch was upstream of the fault. Battery was dead before anyone noticed. Put a second fuse on the control side too. It costs three dollars and prevents an hour of troubleshooting you don't want to do at 2 AM. Gall specifies 80 to 100 inch-pounds on the motor terminal bolts. Not foot-pounds. Inch-pounds. These are small spade or ring terminals on a cast housing. Strip them in ten seconds if you're sloppy with a socket. Use a torque screwdriver or a small click-type torque wrench with an adapter. The vibration from a running siren at 1500 RPM will loosen under-torqued connections fast. Over-torquing cracks the housing around the terminal boss. Both outcomes leave you with a dead siren and a bill for a replacement motor assembly. Do a bench test before you mount the siren in the final position. Connect battery directly through an inline fuse and a momentary push button. Listen to the tone. Check amperage draw with a clamp meter. Note the resting amp draw versus the loaded amp draw. If the resting draw is above 5 amps on a TS100, something is wrong. Likely bearing wear or armature rub. If you find that during your test, fix it now. It is much harder to diagnose after the unit is bolted to a truck frame with limited access.
I once installed a perfectly good TS100, wired it up, and it sounded weak from the start. Took three hours to figure out the tone chamber gasket was installed backwards, sealing off one chamber. The siren was running but only producing one tone. The unit looked fine visually. The specs on the website for the TS100 showed two tones, which should have tipped me off earlier, but I was rushing. Don't rush this. Five minutes of checking the chamber orientation before you bolt the housing saves hours of confusion later.
