SMC valve frozen in open position, question for you guys....

Hoping some vendors will give some advice and/or those of you who’ve been in the scene for some time can shed some light. I have a 1/2" nickle plated SMC valve, which has worked flawlessly from day one. My horns are now on my 4th vehicle, with all of the original parts since day one (Vaair has rebuilt my pump within the last year or so). I do know the risks of improper storage, especially with his hardware just sitting around on the garage floor like my stuff has in the downtime between vehicles…so I can only blame myself for having a mechanical issue with my valve.

Anyone else had a sticking valve before? I am hoping so, and someone has good advice on getting it cleaned up and back into functional shape. I just don’t want to use a chemical that will hurt it, I was thinking about spraying a penetrating oil to free the valve up (after confirming no foreign debris is causing the sticking valve first, of course).


Thanks :cool:

On the SMC VXD Series Valve on page 31 of 32 there is a listing of appropriate lubricants.

Never even ran across my mind to check their site, thanks. :cool:

That answers that too…lube it once, lube it regularly from that point on. So, I’ll hope I can free it by hand…

Watch “Valve” on YouTube

OK guys, what do you think? I know the valve doesn’t sound right, its surely not opening all the way. Electrical failure? Can I buy the electrical part by itself? I took the valve apart, the valve is dry and diaphragms are in great shape…

Also, does the way the relay is indexed make a difference? I know it just pulls the plunger up, but curiousity…

Is there pressurized air on one side of the valve?

The coil is energizing and something is moving / clicking.

There isn’t…because something in the valve is causing it to stay open. The normal audible click from the valve is much more pronounced and there normally is much more mechanical movement. If I flip the compressor on, the horns will start sounding after 4-5 seconds…

The valve has a threaded body to permit maintenance.

Has it been disassembled for maintenance? What was found?

Bottom of post 4, everything was clean and dry…all diaphragms in great shape.

Yes, the diaphragm is accessed by removing the four screws.

The solenoid plunger is accessed by unscrewing the coil. Has the plunger been inspected?

100% disassembled and inspected, nothing dirty/corroded/out of place…looked nice and clean inside.

Does the plunger move freely?

Does the plunger suck hard up into the body when the coil is energized?

Is the plunger attached securely to the diaphragm?

Is the spring intact?

Running a valve in REVERSE will often cause it to malfunction. Make sure the airflow follows the arrow cast into the valve body.

Yup! I made sure to triple check that when installing, on every install for each vehicle I’ve had these on. :slight_smile:

Hopefully I’ll get time tomorrow to take the valve back off…I’ll take it apart again and get some pics, to see what you guys think.

Any news?

Going to try this week to either get a friend over to active the solenoid from the switch…or bypass the switch and just manually activate it from underneath while I examine the plunger.

I might go ahead and take it back off tonight and dissect it again with some pictures. Unless I missed something obvious, I think the problem has to be in the windings of the coil…

Maybe the problem is related to exceeding the operating pressure rating on the SMC valve.

On page 20 of 32 of the SMC VXD Specification Document for the ½" valve, the maximum operating pressure differential for the DC-coil valve is either 0.7 MPa (101.5 PSI) or 1.0 MPa (145.0 PSI), depending upon the valve part number.

The SMC valve part number that came w/ my horn purchase is VXD2130-03N-6G1-B, so my 12VDC / 3/8" NPTF / 10mm Ø port valve is rated for 101.5 PSI operating pressure.

My plan is to run my system up to 200 PSI, so this valve is not appropriate.

What is the part number of the problematic SMC valve?

That link identifies the SMC part number as: VA-8N.

That appears to be a partial part number.

Here is an image of the label on my SMC VXD2130-03N-6G1-B valve.

Mine is a VXD2140-04N-6G1-B-X676.

I ordered a new valve a few days ago, found it at my door today. I was pretty excited, enough so to dress down from work and crawl underneath the Trailblazer SS in the garage…dripping wet even from the rain.

I took the valve out. When I removed the air line from the tank to the valve, some pressure bled off…it was a low amount, but I haven’t run the compressor in around 5 days. To top that off, I didn’t run the compressor more than 10 seconds…since the valve was sticking. I immediately tossed in the new valve, and I am good to go.

Still curious with my old valve, I took it apart again. I seemed to have not put much thought into one area, as indicated below. As you can see, everything looks great…until the last pics. Excuse my fingerprints on a few pieces…

And here is where I suspect my issue is. That is quite a bit of corrosion, and being the coil conducts through this point to move the plunger…I believe the corrosion is preventing the correct operating voltage from transferring through.