I have a Ruud deluxe 80 plus heater. The unit is running, the pilot light is lit, still no heat.

You may have a bad thermocouple. This is a device that when it gets hot (usually from the pilot light) enough it sends a signal (allows conductivity) which allows the heater to stay lit when switched into the 'heat' or functional mode.
It's a common safety element in all gas furnaces and stoves to ensure that the pilot says lit and no gas can escape in case it somehow extinguishes.

If it's a direct spark ignition type heater maybe that's how it's designed to.work .When called for heat pilot open allowing gas then ignitor spark and ignite the pilot then gas valve open and allow gas through burner then unit fires off .
Once temp is met pilot valve closes and pilot out .

Hi, There is no pilot and the flame is lit by a hot surface ignitor... The hot surface ignitors go bad frequently...you probably need to replace that...

Here is a tip that will help you try to figure out why your furnace is notworking.

BasicFurnace or Heating System Troubleshooting

heatman101

If you have cold water now, you should hear the unit fire up and run while heating water. Proceedure would be; pilot is lit with thermostat at pilot setting. Once pilot is lit, you turn up to desired temp setting and you should hear the heater running. Depending on lighting, you should be able to see it slightly brighter and may flicker some while heating.

Need furnace model number. It sounds like you're looking for a standing pilot. Your furnace might not have one. Very likely to have a spark ignition type system or hot surface igniter.

Short answer, yes. However you could have another problem. Replace the thermocouple that keeps the pilot lit. You can get a universal one at any good hardware or farm store. Make sure the new thermocouple is well into the pilot flame. If the blower knocks out the pilot flame again, I would be suspecting cross contamination from a crack in the heat exchanger. As the exchanger heats up, it may be causing a small crack to open and allows the blower to extinguish the flame. It may also be causing a leak of Carbon Monoxide into the heated room air. I would get it checked out very quickly.

THERMO COUPLER PREHAPS, BUT USAULLY THEY WORK OR THEY DONT, I WOULD CHECK FOR BACK DRAFTING AND PROPER MAKE UP AIR FIRST, FOR EVERY B.T.U. 1 SQUARE INCH OF FRESH AIR IS NEEDED.

The pilot light has to be lit before gas valve will operate. That's a safety feature so the valve won't open and fill the garage with gas and possibly cause an explosion or fire. If you have a standing pilot and can't get pilot to stay lit, it's usually the thermocouple and it will need to be replaced. Once the pilot is lit, the gas valve comes on and heats the combustion chamber up to approx. 100° to 125° a thermostat controlled fan switch will close and bring the blower on.

Do you have the serial number or the manufacture date? There are some design changes and I would need to know the year of manufacture to assist accurately. Usually it is a relay or the thermocouple connection that will affect the unit staying lit.

thermocouples you can buy from any heating spares oulet or national energy a hone well is most common for useing as a replacement