This was the most difficult part of working on this Bobrick hand dryer–getting it off the wall!  The pictures I have below are from when I re-mounted it on a piece of plywood in my basement to take a bunch of pictures for this write-up.  When I was originally trying to remove it I kept unscrewing the screws but they won’t fit out the holes because you are supposed to SCREW THEM IN to remove the cover.  You must tighten the screws to remove the cover.  The screws are 5/32″ allen headed.  Here’s a look at the cover screws from the bottom (while the dryer was sitting on my workbench):

The Cover locking screws are inside the holes circled in red

Screw IN the two allen-keyed bolts to remove the cover:

Screw IN the lower bolts to release the cover

Here’s a back-side view so you can see what’s going on–you’re raising up the head of the bolt out of the hole in the metal grating so the cover can come off:

The view from the back when you are raising up the heads of the cover locking screws

You don’t need to screw them ALL the way in but you ought to give yourself a quarter of an inch of clearance.

This cover is SUPER HEAVY DUTY, is made of porcelain-covered thick cast iron, and weighs about 50 pounds so be careful.  It’s a little bit tricky to remove the cover.  The easiest way I found was to lift up on the cover and rock the top out so it unhooks from the spikes it hangs from:

Lift up and pull the top out

Here the top is unhooked

The cover is coming off

Here you can see the 3 spikes that the cast-iron top hooks onto:

A closer look at the spikes that the cover hooks onto

Here’s what it looks like on the inside:

In the picture below I am testing to see that the power is off with my Fluke Digital Multimeter and magnetic strap on the right two electrical connectors–the power is on!

Checking to see if the wires are hot–they are 120 Volts AC hot!

I didn’t actually turn off the power when I uninstalled the hand dryer and just disconnected one wire at a time and put a wire nut on it.  You need to be very careful if you are working with hot wires and it’s really not recommended unless you are a professional.

This was one of those repairs where I had never worked on this appliance so I was just going to take it apart and look inside.  I knew it was operated by some kind of electric eye that detects when your hands are below it and I could see the LED’s for that:

The infrared LED and receiver LED that detects when your hands are under the dryer

I honestly didn’t think anything looked bad when I looked at what you see in the picture above.  Then I noticed that there was a loose plastic cover shoved back farther under the vent:

The top of the plastic box that encloses the electric eye circuit was out of place

The view from the other side:

What was happening was that the cover that shields the LED that is sensing the reflection of the infrared light when you put your hands under the hand dryer was not shielding it and light was leaking in and constantly triggering the fan so that it would not come on when you wanted it to and would randomly come on at other times.  Keep reading to learn how to fix it…Step 6: Remove the grill.  Remove these two phillips-head screws from either side of the grill:

Remove the two grill screws

Here’s the grill removed:

Step 10: Re-mount the switching circuit box by reinstalling the two phillips-head screws:

Re-mounting the box

Step 11: Re-mount the dryer’s grill.

Make sure the rubber gasket that slips over the edge of the grill is back in place before you re-install it.  Here you can see that on the lower right corner it has come off:

Dryer grill gasket has come off the lower right corner

Here the gasket is back on correctly:

The rubber gasket is correctly installed over the outside edge of the grill

Grill Screw details

The grill fits around the LED eye lens that sticks out.  Reinstall the two phillips-head screws on the grill:

Here the grill has been reinstalled

Step 12: Zip tie the cover on.

This is an optional step but somehow the cover found its way off and I didn’t want it to happen again so I put a zip tie around the cover as seen below:

Put a zip tie around the black box to make sure this doesn’t happen again

Clip off the zip tie just to be neat:

Trimming off the zip tie

Step 13: Test the Bobrick dryer.

Turn the power back on and put your hands under the vent.  You must be careful because the wiring will be hot.  You don’t want to put the cover back on before you test it!  It should come on immediately when you put your hand under .  I recorded a little video of me testing out this dryer so you can see how it is supposed to operate:

Step 14: Turn off the power to the dryer.

You don’t want to accidentally touch a hot wire with the cast iron cover and with the dryer working now it will activate on you and scare you to death!!  I have to admit I went to put the cover on one time and the thing kicked on and it surprised me for sure 🙂

Step 15: Reinstall the cast-iron cover.

You would think that you should hook the top of the cover on the spikes that hold it in place and the rock the bottom down into place but the vent gets in the way.  You need to start by putting the bottom part of the cover in place, over the vent opening and then raise up the top and hook it on the spikes.  Put the cover on by leading with the bottom edge like this:

Start by leading with the bottom

Push it on until the bottom edge touches the wall:

Keep pushing on the cover till the bottom edge comes into contact with the wall

Now push the top edge towards the wall and lift slightly to help the spikes find their holes in the cover:

Lift up on the cover and push back the top toward the wall

The cover should be flush with the wall:

The top should be flush with the wall

Step 16: Lock the cover on.

Back out the two allen-headed bolts on the bottom until they press into the hole on the lower grill to lock the cover in place:

Back these screws out until they press into the hole, holding the cover in place

Now you’ve repaired your Bobrick B-700 hand dryer!  If anyone is interested I took a picture of the hand Bobrick’s schematic:

Schematic for Bobrick B700 AirCraft Dryer 20A

Other Relevant Links:

• Manufacturer’s Product page: B-700 115V AirCraft Surface-Mounted Hand Dryer