Grohe Thermostatic Valve spindle and temperature range settings

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by James Nadir, Nov 3, 2019.

  1. James Nadir

    James Nadir New Member

    Nov 3, 2019
    San Jose
    Hello everyone,
    I am new to the forum and have very little knowledge of plumbing. Please forgive any incorrect usage of words and descriptions. I searched the forum for similar problem but didn't find anything. If there is a previous discussion please let me know.

    I have two Grohe thermostatic 34902 shower valves in my home. They were installed in 1998 are about 21 years old. Not surprisingly, water is leaking from both temperature control cartridge. I purchased replacement cartridges from Chicago Faucet.

    1. The temperature control handle is a lever rather than a round knob. After installing the valves, I noticed that lever moves very easily. So easily that the weight of the handle changes the temperature (the spindle moves almost without any resistance). Is there a way to adjust the resistance of the spindle?
    2. The new valve valve doesn’t have the temperature range of the older valve (I get either very hot and a “warm” cold, or a very cold and a lukewarm “hot”). I think the range may be controlled by the “green cap” that screws on to the bottom thread of the cartridge valve (pictured below). It has a small plunger on the inside and its outside has ridges to grasp the handle lever. My guess is that turning the handle lever moves the green cap forward or backwards on the valve which in turn pushes the cap’s plunger against the valve (diaphragm?) that controls the temperature. On the outside of the green cap is a key to correctly position the cap. I am thinking that if this isn’t set correctly then I may have a limited temperature range since the plunger isn’t moving as much as it could. Today, I just tightened the green cap until it's plunger just touched the valve's diaphragm. I don't know how to align the key on the cap.
    Any help will be greatly appreciated.


    Last edited: Nov 3, 2019
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