To upgrade your FR-4102  desoldering pencil to the FR-4104 desoldering pencil you must change the following parts on your current hand piece 

1: Heating element : The heating element (A5029) found on the FR-4102 must be changed out with the ( A5056 )heating element for the FR-4104

2. Nozzle enclosure : The nozzle enclosure ( B5153) found on the FR-4102 must be changed with the  ( B5222 ) enclosure for the FR-4104

3. Movable joint : The movable joint ( B5063 ) is needed for part of the nozzle quick change feature 

4. Wave spring : The wave spring ( B5064) is needed for part of the nozzle quick change feature 

5. Joint cover : The joint cover ( B5062) is needed for part of the nozzle quick change feature . 

6. Screws : The screws needed to secure the heating element are the same for both handpieces ( sems M2.6x 8 sus )  ,  (1) additional (M2.6x8) and (1) (M2.6x4) Sems screw is needed for the wave spring  

Steps : 

1. Remove the (4) screws securing your heating element to the grip . 

2. Remove Heater assembly from grip 

3. Install new heater ( A5056) to the grip 

4. Secure Heating element with the (4) M2.6 x 8 screws 

5. place the motive joint onto heating element followed by the wave spring ontop 

6. secure joint cover to the heating element using (1) sems M2.6x8 screw on the lower hole and (1) sems M2.6x4 screw on the upper hole 

7. place nozzle onto heater and install new (B5222) enclosure over the nozzle . 

Your handpiece is now upgraded to a FR-4104 .