MICO  02-620-009
NAPA      57515
TSM   3800 - $280

This Lock requires 12 volts to activate the Brake lock, the brake peddle is pressed and the brakes are locked. Then the power can be removed and the brakes will stay locked until the Brake Peddle is pressed again.


 The problem is that the rear brake line at this location is a 9/16-18 fitting.  This is just not available to 1/8  pipe which is the current standard and what is used on the Mico Brake Lock. This is not easy, it looks like the best way is convert the rear brake line to the standard 1/8 pipe brake line connectors.  This requires removing the original 9/16-18 fitting from the rear brake line and  reflaring  the brake line in front of a new 1/8 pipe connector.  The combination valve is adapted to the 1/8 pipe fittind using a 9/16-18 to 1/8 pipe adapter (Edelmann number 121040).  This way, if there is ever a problem with the brake lock, the rear brake line can just be moved over to the combination valve and the brake system is in the OEM configuration.

Here is how to do a double flare



 What this provides is a backup for our low-function Parking Brake, and something that will work with any combination of disk brakes and drum brakes. The Mico Brake Lock is a clever little bug that is not apparent from the product descriptions or the operation manual.  

I was worried that if I forgot to turn off the brake lock Toggle switch some evening, that it would drain on the battery all night.  Not so, there is a   pressure switch called the Arming Switch that only applies power to the brake lock when the brake peddle is pushed.  So even though you have the brake lock toggle switch in the ON position, no power is drawn until you press the brake.  When you release the brake, the power goes off, and the lock holds mechanically.  If you pump the brakes, the Arming Switch reapplies power so that the new pressures setting is accepted and the lock is reapplied.  So the device requires no continuous power and you can leave the toggle switch in the  ON position as an indicator that you have the brake lock in operation.  When you want to release the lock, you just turn off the toggle switch and push on the brake.

Mico encourages you to wire the exit pressure switch to the car horn so that if you have the Brake lock turned on with the toggle switch, and you ever loose pressure on the brakes (like your old wheel cylinders are leaking)  the horn will sound and warn you that you are about to slip into the river.  I don't want to warn every one in the camp that I have a leaking system so I  use an alarm inside the coach.  Since you can leave the Brake lock power switch on without drawing power, this feature does not cost you any power from the battery.

In case you  do not have a backup vacuum Pump,  it seems to me this lock could be a life saver.  The problem is when the engine stops, you get one pump on the brakes.  With this, you can flip on the brake lock, you can capture that one pump, and any additional pressure you might be able to generate with the adrenalin assisted, two handed, pull off the steering wheel, stand on the brake peddle.  Might just save your bacon.

Mico and everyone says "DO NOT USE THIS FOR A PARKING BRAKE" which is of course is what we are going to do.  The reason they say this is the Brake Lock is not full-proof enough to be a primary  hand / emergency brake.  There are several elements  in this system that could fail and release the brakes. So to protect their Back sides, they have to say this and the DOT agrees.  Gene
The 02-620-009 MICO 12V. Brake Lock is still being manufactured and is available through MICO distribution.  Due to changes in vehicle brake systems, this lock is not recommended for any on-highway applications, although it remains popular for forklifts and other off-road vehicles & machines.  MICO would recommend you choose a brake lock other than the 02-620-009 for your motor home.

The MICO web-site  <mico.com> contains information on other MICO locks and information on distributor locations.

Thank you for your inquiry.Tim AndersonMICO Sales 


If you add a hidden or key switch to supply power to the brake lock, you have an excellent anti-theft device for the GMC.  If any one touches the brakes while trying to steal or move your GMC, the brakes will be locked on and it would be necessary to lift the rear of the coach (8,000 pounds) to move the coach.  


The hydraulic line lock is basically a valve and available in either a manual or electrically activated versions.

The problem with a manual type is that it has to be in close proximity to the driver so that you can activate it.  To operate it, you pull a knob to activate and depress the knob to deactivate, all the while you are depressing the brake pedal.  It's analogous to pulling out the headlight switch to turn on the lights and pushing it back in to turn them off.

What the above means is that the valve, which fits in you hand, has to be plumbed into the rear brake line.  That would mean you would have to route it into the driver area interior of the coach.

The other type, also plumbed into the rear brake line, is activated by an electrical switch, which you can see is much more convenient in that it can be located anywhere you want in the drivers compartment area.  See this site for an example of the electrically operated line lock:  www.mico.com , which is the one Leigh Harrison supplies.  The one I purchased from Leigh in 1995 is P/N 02-620-009.  I didn't locate that number on Mico's site, so perhaps they have renumbered??

I did look at their 690 Brake Lock System brochure and note several interesting systems they have - lever lock, twist lock, and single lock (a cable operated for remote locations).  Guess I'll have to call them and see if there is a etter Mico application.Paul Bartz

Jamar Performance Products.
Thanks to Dave Lowry
for the Pictures

The problem I have with the unit, is the interior passage way,  is very small and I think it limits the response of the rear brakes.  I have decided not to use this unit.

These pictures are provided by Dave Lowry ,GMC Owner.  He has had good luck with this brake lock with the exception that it will sometimes lock up when the brakes get real hot.   I really like the operation of this lock because it cannot be applied accidentally.  The operation is : press the button, then press the brakes, then release the button.  The brakes will remain actuate until the brake peddle is pressed again.


The mounting is very easy and only the rear brakes are effected.