I have a price pfister three handle shower fixture, when you take a shower the temp goes from hot to cold. From the spout you can regulate the temp fine.

Are you saying that you have a three handle tub and shower valve, hot, cold and diverter and that when using the shower head the water temperature goes from hot to cold and then back to hot? Are you saying that this does not occur when using the tub spout?

Does your water heater have heat trap nipples?

Price pfister three handle shower fixture. When hot and cold is adjusted from the spout you can get it to a comfortable warm temp. When you divert that same water to take a shower it gets scalding hot. On the knobs cold is wide open while the hot is just bearly cracked open.

Suspect you either have debris trapped in the valve or a loose washer. Remove diverter valve, open hot and flush valve, open cold and flush valve. Check washers on diverter valve. Turn off water and remove hot and cold valve stems. Briefly turn on water and flush valve again. Both hot and cold. Check washers on valve stems.

Three handle tub and shower valves, though sold, are illegal to install because they do not have a pressure balancing mechanism (why you have the issue you have), or a temperature limiting device. Here, as much as it will appear that your tub spout is maintaining a balanced temperature you aren't showering using the tub spout so you wouldn't notice the imbalance between hot and cold water like you would notice the issue when using the shower.

The only way to fix the issue will be to install a single lever, pressure balanced anti.-scald valve.

Back to you...

Mark

Mark,
I would be willing to bet that this valve is older than you are.

Yes it is old, the bldg. was built in '78'. Thank's hkstroud I will try what you advised.

Obviously... exactly why I pointed out all the information I presented. As I said, there is no fix to this other than replacing the valve.

Mark

qcat1, let us know the outcome.

Question, has any work been done on the plumbing, (soldering of pipes) any where in the house in the last year?

Water conservation project was done, low flow toilets, low flow shower heads, low flow areators.

Flush tub valve as described. If any soldering of pipes was done the most likely thing blocking tub valve is a bead or wafer of solder. When soldering pipes if too much solder is use, the hot solder will run down on a cold pipe. It doesn't stick and the flow of water will carry it to the next available valve. Most likely a bit of solder is blocking the cold side of tub valve.