Understanding the new Happijac system

This article is to give a brief summary of the new model components and how they interact with the older models. While most parts are interchangeable care must be taken or you can damage your legs, or jacks as they are known in USA. 

The Legs or Jacks

Happijac now make only two models of legs - the 4820 and the 4220. The 4820 is 3" or 75mm longer than the 4220 and has a greater load bearing capacity. This model replaces the 4800 which was the same length. The additional length is handy in Australia where we load campers onto trays that tend to be higher than the American tubs of utes or pickups. Being the same cost I would recommend anyone buying a full set of legs to get the 4820’s. The 4220 effectively replaces all the other Happijac models, including the 4150, 4160, 4500, 4560 and 4600. The fitment of the 4820 and the 4220 is the same as the previous models. They fit the existing mounting brackets and the motors, both new and old models. There is one difference in that the 4820 and the 4220 are fitted with a rubber bushing to prevent any sudden stop from overwinding the legs up or down. More on that in the new motor section. 

The New Motors 

The old style motors (model 182515) had a built in clutch system designed to prevent the motor from destroying the gears or the motor itself, if the motor was overwound. Should you reach the end of the jack you would hear a clicking noise, which was the clutch saving the leg from extinction. In theory this was a good idea but in practice the clutch would sometimes engage randomly, possibly due to corrosion in the leg. A lot of the old style motors had to be replaced from the clutch failing or just wearing out. 

The old motors were replaced with new Vertical Orientation Clutchless Current Sensing (CCS) Motors. These new motors are quieter and more reliable. Obviously they have no clutch which has been replaced by the Current Sensing System which detects that the leg is fully wound and shuts the motor down to prevent damage. This is why they have put a rubber bushing in the new legs to prevent the leg from coming to an instant dead stop and give it the split second it needs to shut off. For this system to work it requires a CCS Control Board and Remote Control unit. 

While the old Control Board and Remote will operate these new motors, when the legs are fully wound in or out there is no clutch and nothing to tell the motor to stop. So if you are not watching and continue winding, the motor might do serious damage to the drive mechanism in the leg or the motor itself. To be safe, if you are putting new motors on old legs, you should also replace the Control Board and Remote unit. Even if you are only putting one new motor on you should have the new Control Board/Remote. By doing this the new motor that you have installed will stop using the CCS system and the other motors will stop using the clutch and/or the CCS. 

 While the new Vertical Orientation CCS motors fit exactly the same way as the old motors, there are a couple of problems. The new motors are slightly larger in circumference. So if your legs were fitted flush against the side of your camper then you will have to fit new brackets to bring the leg out a small amount. The new brackets are readily available and not that expensive. 

The second problem with the Vertical Orientation motors occurs when they have been fitted under the bedroom or cabover of the camper. There is often not enough room to fit the new motors without moving the mounting brackets for that leg.. 

Old Motors.

When the new models of legs, motors and remotes was introduced, Happijac ceased production of the old models. Eventually they ran out of stock of the old models and then people became a bit upset when the could not get a replacement motor. Fortunately they are now manufacturing the old model motors, but the old model remotes and control boards are mno longer available. 

The New Control Board and Remote Control Units 

These new units are specifically designed to work with the new motors and the new legs, using the Clutchless Current Sensing System to protect the motors from overwinding and possible damage. However they will also operate the old style motors quite safely as the the old motors clutch system will still work.