What the heck is the deal with the GL air suspension

[MB140300SD]

I have a 08 GL320 that the wife drives. She uses it to pull a small 6x10 enclosed trailer to shows. I would guess it weights probably 2-3k lbs loaded. Anyway, it has about 245k on it now and I bought it with 207k. Right before I bought it all the air struts as well as the pump was replaced with Arnotts.. Not too long after I bought it the left rear started dropping overnight so I replaced both rear bags with Arnotts. Soon after, the pump went out. I attributed it to the air back leak and replaced it. She then started towing this trailer on occasion. No issues at first but then while she was 3 hours away she calls and says its on the ground. I drive up there and find the pump not running. Fuse blown. I replace it and it pumps back up. Soon that pump then goes out. I replace it again along with the valve block just to be sure. By this point everything in the system is pretty much brand new except the front struts which were replaced right before I bought it. Wife towed the trailer a few more times and guess what, pump goes out again sounding like its full of rocks. I replaced it for the 3rd time since I have owned it and the thing has been driven a little bit, but has been sitting in the driveway with the trailer attached to it for at least a couple of weeks and has not dropped an inch. No leaks anywhere. If it had leaks it would not stay at the proper height for weeks at a time.



Wife towed the trailer maybe 100 miles since the last replacement, then another few trips to town in the last couple of days. Yesterday she drove it 3 hours to a show and just called to say the truck is on the ground again. WTF? I told her to check the fuse when she can and get a replacement if blown, but who knows if this pump will be bad like the rest have been. It seems fine until you start pulling a small trailer with it. My assumption would be it has a leak, causing pump to run too long which blows the fuse, but as mentioned it stays up for weeks, no leaks. Perhaps there is a wire shorting to the pump, but again, how would that cause the pump itself to go bad? Are Arnott pumps just junk now days? What am I missing?