I have the Pac-Brake, the customer service has been very good.
But after nine months of trouble free use and extreme happiness, the relay went bad, got a new one and it was never just quite the same, 6-8 months later the the relay was replaced again. Didn't fix the problem so the tests showed that it was the solenoid that went bad. This worked on and off for about 3 weeks when the compressor was filling my 2 1/2 gallon air tank after about 3-8 activations of the exhaust brake. All of this was being done at a shop that Pac-brake sent me to so it was done by people that were suppose to know what they were doing. Pac-Brake paid for everything parts and labor up to the solenoid, which they covered the part and then I got a bill. That instantly turned me into the mechanic, and not a good one at that.
Numerous calls to Pac-Brake and tests on my part, I replaced every air line and fitting, adjusted this that and the other thing, unhooked this and hooked up that, we finally determined that the air compressor itself was bad, they sent me one free even though it was officially out of warranty. It still did not work properly and then we figured out that the piston that moves back and forth was bad. They sent me one of those that I finally put on last Saturday (7 days ago) so far so good.
I have heard of very few problems with any exhaust brake I think I just got the bad one. Scheduling to get into the shop when they were working on it and my time to do things and shipping of parts all totaled my brake was down 6 of the 20 months that I have had it. With the first 9 months being fantastic.
To be fair if scheduling and I had some more free time (we are building a new house) the total down time would have been about 3 months. Their customer service has been very good.