Slide Out Interlock Modifications

Introduction

The Allegro Bus comes with slideouts which extend to give much more living space once parked. Originally these were the Power Gear slideout mechanisms which allowed the main driver side slideout to extend and then drop down, giving a flat floor. In later years, additional slides were added to increase the total number of slides. Today's RVs typically come with four slides. In order to prevent these slides from extending while driving, a safety interlock system was provided to lock out the operation of these slides until parked. My 2004 Allegro Bus 40DP had two slides, both of which were on the driver's side. These slides were powered by an electric motor which drove a mechanical rack and pinion gear mechanism. In order to operate these slides an interlock solenoid was installed between the power source and the slideout motors. This solenoid was not a typical solenoid in that it functioned in reverse from most solenoids. It closed the circuit when the power was removed from it rather than when the power was applied to it. This type of solenoid is referred to as "normally closed" rather than "normally open". The solenoid was connected to the ignition switch so whenever the ignition key was on the solenoid would engage and break the circuit to the slideout motors. If you wanted to operate the slides you needed to turn the ignition key to the "off" position. This worked fine when parked but if you ever wanted to warm up your engine and then retract your slides you were out of luck. But, the biggest issue is that this solenoid, which looked identical to the Charge Solenoid, was an oddball because it was wired in reverse. This meant it was not readily available so Tiffin looked for a different way to do things. In 2006 or 2005 Tiffin changed this design to use a standard "normally open" slide interlock relay. This meant that the solenoid was identical to the Charge Solenoid, which was readily available. This also meant that now the ignition key had to be in the "on" position rather than "off" in order to operate. That would lose the ability to lock out the slide motors when driving. In response to this, Tiffin lifted the ground wire from the solenoid and routed it through the park brake switch. Now whenever the park brake was released the circuit was open and the slides could not be operated. The drawback to this is that you need the ignition key to be on in order to operate the slides. Most generally if you are parked you will remove the key from the ignition so if you want to operate the slides you need to re-insert the key. Plus, every time you turn the key on, all of the low air pressure buzzers go off, the jacks down alarm buzzes, the entry step retracts, and lights flash all over the dash. My solution was to install a time delay relay to power this circuit as well as a momentary rocker switch. One tap on the rocker switch and the relay engages to energize the circuit to the interlock solenoid. The relay will remain closed until the timer kicks it out. The time delay is adjustable but I chose to set mine at 5 minutes. That gives me plenty of time to "'arm" the slides and retract them. If I get distracted and don't finish up within 5 minutes all I have to do is tap the switch once again. Note that the interlock solenoid is still grounded through the park brake so once the brake is released the slides are locked out regardless of the relay's position. I know have the ability to operate the slides any time I want without requiring an ignition key. It also means I no longer have to listen to all of the alarms.

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Mark Quasius - "Cruzer"

The Installation

The above image shows the monitor panel. I installed a SPST Momentary illuminated rocker switch at the top right, where there was an empty space in the panel. The switch is the same basic design as the Aux Start and Tag Dump switches on the driver's side console.

I removed the monitor panel and placed the relay in the position showed. To mount it I used some industrial duty Velcro and attached it to the relay body as well as the plywood partition behind it. I then connect power and ground to the relay, two wires to the rocker switch, and then ran one long wire back to the slideout interlock solenoid in the rear curbside compartment.

To operate the slides I simply press the switch. The switch itself lights up while the relay is powered up to help indicate that you have power to the slide motors. I used a label making machine to make a black ink on transparent tape label that identified the switch.

Summary

I now no longer am tied to the ignition switch when I want to operate the slides. I still have the secondary safety feature of the park brake as well as the timer cutout cycle so there's no worries about unintentional slideout operation while driving or parked.

This review written 3/16/08