Batboard

I have a customer that has about 40 Mototrbo moboiles. 6 of the units are installed in International trucks(various models) The radios will at random shut off when the truck is driving down the road or even when they are parked. Several also are staying powered up but the dispalys start flickering rapidly and the radio goes off into lalal land. Some have ignition sense tied to the batteries, some do not(testing purposes)
The radios are obviously losing power momentarily.

Has anyone experienced this? If so what was the solution?

CDMs do this with undervolt issues...

I have no experience with trbo mobiles, but this definitely sounds like a power issue. Go back over your installs and verify the workmanship especially on the grounds. DO NOT ground at the battery, but ensure the black lead is secured under the OEM chassis ground screw, not just to a hole drilled in the body that might return through four welds, a couple bolts, and some frame brackets. Even after all that, sometimes mobile equipment can be sensitive to noise, spikes, and fluctuations on the line that no amount of passive filtering will clean up. I've used buck-boost converters with great success to flatten out power problems, and keep MDT's alive even during engine crank and lift operation.

This product is pretty good: http://www.powerstream.com/dc2.htm

9-15V in gives 13.8v at 15A, and most units test well all the way down to 6v input. With a normal battery pack the driver can have the engine off, have every light on for 20 minutes, run the hydraulic lift up and down several times, and restart the truck without resetting the MDT. It's about the size of a car stereo amplifier. No internal batteries to maintain and replace. Plenty of capacity to drive most modern equipment. They're cheaper than a couple service calls chasing power gremlins. AND, with hundreds of these in service, the worst problem I've had is bearing noise from the fan.

The buck boost converter is the type of answer I was looking for.
The customer does his own installs, which I frown on, but he did a very good job. Proper crimps and locations for power and ground.
A big thing that has thrown them is they left Maxtracs which you could just hammer the power to and get away with.
I did some testing in the shop and both radios could go down quite a bit in voltage and stay on. The Trbo radio can be powered down on the bench with the ignition sense tied to A+ and always recovered. I suspect there are some funny things happening on those trucks like some sort of brown out that ends up putting the radios into a state they cannot recover from.
I looked at two things but had not purchased either yet. A Nav-Pac (mucho bucks) and also considered a 1 Farad cap like used in car stereos, but am suspicious they will only catch it some of the time.

Thank you for your replies.

Yeah, you're welcome. Hope that helps. The buck-boost was a satellite solar power concept that moved to the terrestrial solar power industry, and then into automobile racing so you could take the alternator off and get a few more horsepower to the wheels. I got my first one from Racing Radio, and then bought from these guys directly. LT (Linear Tech) makes several chips that do all the regulation, and you can roll your own circuit from their app notes. I made a few with wider input voltage ranges for low current applications (a compact solar powered water quality monitoring system). Neat stuff.