Moen Posi-Temp Shower water temperature mystery...can you solve it?

[greenfamily]

We have a single handle shower valve control that is original to the 1989 house that we recently purchased. In the mornings the shower water only gets warm, however the sink faucet water is nice and hot in that bathroom. The strange thing is that if we take a shower in the evening the shower water is only hot and we can't alter the temperature by moving the handle. It stays exactly the same temperature. I have done some searching on this forum (just joined today) and think that it is related to the mixing valve, but why does it vary by time of day? I would like to have some idea before getting a plumber out, or even if it may be something we can fix ourselves.

 

[Dana]

It might help narrow down the guesswork if you included the make & model of the shower mixer.

 

[Sponsor]

 

[greenfamily]

The only name I can find on the fixture is Sanadyne.

 

[Drick]

Oddly I have a very similar problem and I also think its the mixing valve. In the morning the first person to shower (usually me) will only get warm water even when the shower is set to fully hot. The next person will have no problems and will have hot water. Sometimes later on in the day the shower water will only be hot. I have two showers and both have the same problem.

I did find a work around of sorts. If I start off the morning by turning on the tub spigot to full hot and waiting until the hot water makes its way up to the tub and then switching over to the shower head 'll then have hot water -- usually. That doesn't fix possibly having only hot water later in the day, but at least I get a hot shower in the morning. The mixing valve is a Honeywell Sparconmix AM Series (ASSE 1016-T, ASSE 1017) . The shower fixture is a Moen one handle tub/shower valve with trim. I don't have an exact model number. The instructions that were included list the following models; L2351, L2352, L2353, L2353P, L2362 and L2363. Everything was installed when the house was built in 2005.