Expbus 2v issue

Working a condition inspection on my bird that also has an intermittent problem powering up the electrical system...The master relay will " chatter" while the relay on the load center " chatters "as well. The master contactor is a negative switched unit and I'm assuming it gets its ground thru the load center. The builder of my bird mounted it high up under the panel with VERY limited access....so I'm going to journey my up there today and see exactly what I've got...it appears to be the 1999-2000 vintage EXPBUS 2v with remote toggle switches. Anyone experience issues with these? Mine got wet from the tip up hinge and light rain 4 years ago....might need to be replaced. Possible relay or connection issue as well...RV6a here....gonna be fun..lol! Any advice on these load centers ? No wiring diagrams either,but it looks simple...just a bear to get to. Thanks

Jim

Search for expbus and you will find others who have had issues with them. Here is one:
http://www.vansairforce.com/community/showthread.php?t=113012

Yep....saw these earlier and was just curious if the relay was easily replaceable. The Stein guys have it right....keep it simple....do a main bus ,breakers and switches. I figure since mine already has one installed....id do a remove/replace on the unit. Based on 4 back surgeries already I'd like to limit my time standing on my head behind the panel.

The Exp bus systems often receives bad reviews, but I love mine. It?s about the same vintage as yours. Early on i blamed it for several problems, but the true cause was always something else.

Your issue may be a weak or intermittent ground. I recommend you add a second (temporary) known good ground wire to the solenoids. If that stops the chattering, you have isolated the problem to a ground wire or connection.

Good luck

Dean Pichon said:

The Exp bus systems often receives bad reviews, but I love mine. It?s about the same vintage as yours. Early on i blamed it for several problems, but the true cause was always something else.

Your issue may be a weak or intermittent ground. I recommend you add a second (temporary) known good ground wire to the solenoids. If that stops the chattering, you have isolated the problem to a ground wire or connection.

Good luck

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I tried to replace mine too but the company was totally unresponsive and I couldn't find a used one and wondered about the good sense about that idea. I just bit the bullet and paid to have my mechanic switch it out. It now works all of the time. Mine would shut the avionics down at the most inopportune times. Stein made it clear that this was the correct path.

Best of luck.
John

Dean...Do you have a part number on your board? Mine just says " doc load buss" with no other numbers. Mine has some indication of water damage from years past. My board is 10" long X 3" wide with three relays on top ( 2 are replaceable) . Mine also has the ribbon plug for the load meter as well. The part pictures I'm seeing look different than mine .

I have an unused Expbus 2V DC Load Center Toggle board that I never installed. If you'd like to try it after the ground-test I'll send it to you for shipping + whatever you think its worth to you. I also have the annunciator panel for it somewhere.

Mine still has the chatter issue after running a new known ground...shoot me a price either by pm or post it here if you like . The newer boards look different with respect to the relays. Mine has 3 on top....and is remote mounted with the switches removed...load indicator is fine.

jim plaster said:

Mine still has the chatter issue after running a new known ground...

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Bummer. I assume one of the relays/contactors is on the Exp board while the other is remote located (not part of the Exp bus))? If this is so, can you confirm operation of this (remote mounted device by isolating it from the Exp bus and checking for the chatter, again by installing a known good ground?

Good luck,

The only other relays in this system are the master and the start contactor. This buss system when it's inop ...kills power to both the start and master contactors preventing both contactors to operate...hence a dead airplane..My builder also helped me out by burying the start contactor high on the firewall...behind the panel as well. I see some crazy stuff on some birds...some guys build them to fly....not to maintain. Right now it's chattering or shutting off completely on the 5th or 6th time the master switch is turned on..creating a electrically dead airplane. I tend to do some traveling with this bird and would like better odds on not being stuck somewhere...Dependability is the issue here. Gonna check with AC Spruce....they're currently NIS

jim plaster said:

Dean...Do you have a part number on your board? Mine just says " doc load buss" with no other numbers. Mine has some indication of water damage from years past. My board is 10" long X 3" wide with three relays on top ( 2 are replaceable) . Mine also has the ribbon plug for the load meter as well. The part pictures I'm seeing look different than mine .

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Hi Jim,

I'm on the road this week, so I have no access to P/Ns, but can get you something when I return, if you have not resolved the issue. My -4 is down for Condition Inspection, too. Forgive me if you already know this, but access to points high and aft of the firewall are easily reached by removing the forward fuselage skin.

Good luck,

Mine doesn't have removable panels aft of the firewall..... Forgive me, but are you suggesting drilling off the fuselage skin to get to these items? They can be assessed much easier than that....still hard to get to, but far less work. Been at this stuff for almost 40 years....far easier ways to " skin the cat" here. This is a 6a...not a 4

jim plaster said:

Mine doesn't have removable panels aft of the firewall..... Forgive me, but are you suggesting drilling off the fuselage skin to get to these items? They can be assessed much easier than that....still hard to get to, but far less work. Been at this stuff for almost 40 years....far easier ways to " skin the cat" here. This is a 6a...not a 4

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Sorry Jim! For some reason I thought you had an RV-4. On those aircraft the forward fuselage skin is removable.

I do maintenance on a 4 for a guy here....I do love the access for sure! All of these birds need at least removable panels,or skins like the 4 has. No service loops in the wires either....it's a bit tight behind there on the 6.