Any suggestions on my dishwasher?

I have a questions about my dishwasher. We just moved into a 60+ year old house on well/cistern water and septic system. We have pretty good pressure at my sink faucet but when I use my dishwasher on hot water it takes approx. 7-8 hours to complete a cycle. Also if I use powder soap with the hot cycle the powder is left on the glasses and some of it is still powdery which leaves me to believe they have not been touched by water. If I use cold water it seems to finish in approx 2-3 hours. This is a 3 year old dishwasher and we were told it worked just fine. Any thoughts on what might be wrong or what to check.

Check the isolation valve that serves the hot water line to dishwasher, probably calcified up.

I am confused because I never saw a DW where you had the option of using cold water. There is only one water inlet. Please explain.

Some more information

Okay, I have a Frigidaire Ultra Quiet III. It has a high temp wash. If I push this button it takes approx. 7 hours. If I turn it off it doesn't take as long approx 2-3 hours. I opened the dishwasher once with the high temp and steam really came out. When I opened it when I had not choosen the high temp option, no steam. It may not have been cold but it wasn't hot enough for steam to come out. That is what I meant. Maybe the dishwasher is toast and I need a new one but if it is repairable I sure would like to.
Thanks again for a great forum and helpful people.

I'm with RUGGED. I'd first check the valve and the waterline to the dishwasher. Really sounds as if you're not getting enough (if any) water to the unit. There could very well be a calcium buildup in the valve restricting waterflow. If you have full flow from the valve through the waterline then I'd call out an appliance repair company.

I'm not a dishwasher expert but..... (and someone feel free to chime in here... )

If you choose the "high temp" option, the dishwasher adds it's own heating element to the process, heating the water to a level higher than that supplied by the hot water heater, right? If so - is the "high temp" controlled by a thermostat? Is it possible her heating element is taking "forever" to get the water to temp, thereby causing the extended time to do a load?

Nanilyn::: When you choose the regular temp option, does it really take two or three hours... or does it just seem like it.... My dishwasher takes about an hour to run a cycle..... though sometimes it seems like two....

You may two problems. First, there may be an obstruction somewhere causing slow fill. Second, depending on the layout of your pipes, the DW may be filling with COLD water, By that I mean that it only uses a few gallons to fill, and these first few gallons out of the pipe could be cold. Try this: Right before running the DW, run the kitchen tap long enough to get hot water coming. Now start the DW. Even with this, by the time the next cycle comes around, it may have cooled off some.

If either of the above situations is true, then the PreHeat option of the DW will further slow down the process, or you could have a failing heater element.