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Any time you have a single handle kitchen faucet the valve cartridge can ware out and go bad over time , this will cause the cold water to mix into the hot and cause that are of the house to have less hot water then normal. By turning on the hot at just the kitchen sink and let it run for a while this will test for this, after a while the kitchen sink should get hot as normal.
If that is the case, can the valve cartridge be replaced. Would this affect the water temperature in the dishwasher as well?
Yes the cartridge can be replaced , a replacement can be bought at a plumbing supply house or direct from the manufacture. Yes this can also cause the dish washer to be affected, the dish washer if you look under the kitchen cabinet is fed from the same hot water pipe as the kitchen sink and when you have a bad cartridge the cold will mix into the hot pipe and cause any water in that section of pipe to get less hot then normal . It is also possible if you have a bath room near by that the single handle cartridge in the bathroom near the kitchen is also causing the problem.
Ok. I will try that tonight and let you know.
Haven't had a chance to check this yet, but will hopefully try tonight.