Emergency service lightbars/beacons on CUCV

I have a Federal Signal Twinsonic lightbar on my M1008, I only use it for a few events a year, so It's got magnets for feet and a connector so I can take it off. The previous owner installed it and wired it up, I just added the inline connector so it can be removed. There is a control box in the cab that switches the lightbar and siren on.

I'm not exactly sure how the last guy wired it up, but whenever I turn it on, it puts a considerable load on the alternators. If i run the headlights and the lightbar at the same time, it tends to make the belts on the alternator squeal, even if they're properly tensioned. I know this lightbar does draw quite a lot of power, but they did use them and other types of lightbar on CUCVs back in the day, so there must be a 'right' way to wire them up.

I don't know if it's an issue with my lightbar or an issue with the way things are wired on the truck, but it doesn't seem right. Has anyone else got a similar lightbar on their truck who could maybe advise?

What ground (earth) source are you using since you made the system removable? Is it a 24 volt system or a 12 volt system? You have the radio antenna set up as well. Are you powering radios while you try the light bar?

We used TwinSonics on our cars back in the mid-80s. If I recall correctly they drew 22amps, and we ran them on a 12volt 25amp fuzed circuit. This was for a bar with four bulbs total (two back-to-back each side on a rotating base, with mirrors in between). They were chain driven by a single motor.
There was also a less common version with a separate motor for each side.

While checking all your wiring, you might want to make sure the light bar motor, chain, and rotator posts are clean and well lubricated. The white grease used tends to harden up over time and can really make the motor work to turn the lights. Cleaning that up and using fresh grease makes a big difference on how well these older bars work. I have Federal Jetsonic and Jetstream light bars on my two M1009s.

Cheers

Barrman said:

What ground (earth) source are you using since you made the system removable? Is it a 24 volt system or a 12 volt system? You have the radio antenna set up as well. Are you powering radios while you try the light bar?

Click to expand...

The radio antennas aren't connected to anything, they are just decorative. The truck is still 24v, but the siren and lightbar just run from a 12v source.

There are three wires coming from the lightbar:
- a ground wire that runs to a sheet metal ground point just above to the parking brake pedal, inside the cab.
- one wire that runs to an aftermarket fuse block on the firewall, through a 10 amp fuse, and then to a factory junction block on the firewall that supplies constant 12v, even with the key off.
- another wire that runs into the siren control box in the cab, through a small 15 amp fuse.

The lightbar currently works as intended, it just makes the belts squeal. I don't know if that 10 amp fuse on the positive wire is maybe not helping things.

M813rc said:

We used TwinSonics on our cars back in the mid-80s. If I recall correctly they drew 22amps, and we ran them on a 12volt 25amp fuzed circuit. This was for a bar with four bulbs total (two back-to-back each side on a rotating base, with mirrors in between). They were chain driven by a single motor.
There was also a less common version with a separate motor for each side.

While checking all your wiring, you might want to make sure the light bar motor, chain, and rotator posts are clean and well lubricated. The white grease used tends to harden up over time and can really make the motor work to turn the lights. Cleaning that up and using fresh grease makes a big difference on how well these older bars work. I have Federal Jetsonic and Jetstream light bars on my two M1009s.

Cheers

Click to expand...

My Twinsonic has 8 lamps, four that are fixed facing forward/back, and two rotators with two lamps each, driven by a single motor and chain. It might demand a little bit more power than other types due to all the lamps.

When I bought the truck a few years ago I cleaned the inside of the lightbar and greased the chain, and it lives indoors out of the weather when not in use. I'm going to replace all of the bulbs, so I'll check the contacts while I'm there.

I'm growing more suspicious of the 10 amp fuse mine is running through, now you mention using 25 amp fuses for a bar with less lights.