I have a Ruud Acheiver 90, I'm having some problems, the rollout (burner) limit switches are opening, and there is an electrical burning smell. It seems that sometimes the squirrel cage isn't kicking on, but when I reset manual limits and give the squirrel cage a manual turn, the heater runs fine, sometimes. I guess what I'm asking is: would the fan motor only work sometimes, would the ignition plug give off an electrical burning smell (it's lighting fine), there is a separate thermocoupling, it seems to be fine..... Filter is new.... Just wondering if the squirrel cage's start/run capaciter would be the cause.... IFC seems to be operating fine... All other systems seem to be operating fine... It's almost like the fan motor is getting stuck, and when it doesn't kick on, the limit opens up... Please Help.....

rollout switch on lower inside cover by burn rack and gas valve possible down draft pushed flames into cabinet and tripped it if keeps happening might need chimney if ok check gas pressure if low unit overheated or burner tube clogged

TRI-COLOR (DSI LED) DIAGNOSTIC TABLE
No. of Red BLINKS
1 Flame sensed when no flame should be present
Verify the gas valve is operating and shutting down properly. Flame in burner assemble should extinguish promptly at the end of the cycle. Check orifices and gas pressure.

2 BLINKS Pressure switch stuck closed/ inducer error
Pressure switch stuck closed. Check switch function, verify inducer is turning off.

3 BLINKS 1st-stage pressure switch stuck open/inducer error
Check pressure switch function and tubing. Verify inducer is turning on the pulling sufficient vacuum to engage switch.

4 BLINKS Open limit switch Verify continuity through rollout switch circuit.

5 BLINKS Open rollout/open fuse detect Verify continuity through rollout switch circuit, check fuse.

6 BLINKS 1st-stage pressure switch cycle lockout If the first stage pressure switch cycles 5 times (open, closed) during one call for heat from the thermostat the control will lockout.Check pressure switch for fluttering, inconsistent closure or poor vacuum pressure.
7 BLINKS External lockout (retries exceeded) Failure to sense flame is often caused by carbon deposits on the
flame sensor, a disconnected or shorted flame sensor lead or a
poorly grounded furnace. Carbon deposits can be cleaned with
emery cloth. Verify sensor is not contacting the burner and is locatedin a good position to sense flame. Check sensor lead for shortingand verify furnace is grounded properly.

8 BLINKS External lockout (ignition recycles
exceeded where flame is established and then lost)Check items for exceeded retries listed above and verify valve is not dropping out allowing flame to be established and then lost.

9 BLINKS Grounding or Reversed polarity Verify the control and furnace are properly grounded. Check and reverse polarity (primary) if incorrect.

10 BLINKS Module gas valve contacts energized
with no call for heat Verify valve is not receiving voltage from a short. If a valve wiring is correct and condition persists, replace module.
11 BLINKS Limit switch open - possible blower
failure overheating limit Possible blower failure, restricted air flow through appliance or duct work. Verify continuity through limit switch circuit and correct overheating cause.

12 BLINKS Module Ignitor contact failure Fault code indicates the module ignitor contacts are not functioning
properly. Replace module.Solid Module - internal fault condition Module contacts for gas valve not operating or processor fault.
Reset control. if condition persists replace module.
3 double 2nd-stage Pressure Switch Stuck Open/Inducer Error
Check pressure switch function and tubing. Verify inducer.

Hello, sounds Like the Furnace is tuning off due to the limit switch or rollout switch opening. A limit switch and rollout switch are safety swtiches that will turn off the furnace if it gets to hot or the burners flames are abnormal. Usually a weak blower motor, dirty blower wheel , dirty burners or even a crack in the heat exchanger can cause this problem. Best bet is to call a hvac technician and have them check it out.

Should be a small button on the outside unit close to where the tubing is welded on the unit. This is a high pressure switch that trips if the unit gets hot , so be sure and check the coil for dirt , etc. The fan pulls air through the coil. If the outside of the coil is dirty it will trip the high pressure switch. Look under the fins, you will see the outside of the coil.

Normally blower should run first and then only furnace will work. check with blower contactor.

How do you test a pressure switch and other limit controls?
This is for people who are experienced with electrical equipment and the use of a Volt Ohm meter. *Please never by pass a pressure switch or limit control. The pressure switch and limit switches are there for your safety. You would test by setting your volt meter to "Volts AC" and test the rollout switch by placing one meter probe on one terminal of the rollout switch and your other meter probe to a good ground. Have the red probe touching the top terminal of the rollout switch and the black probe touching a ground (body) of the furnace. You should be getting 25.85 volts which means the rollout is good on the top terminal. I would next test the bottom terminal of the rollout by touching the red meter probe to the bottom terminal on the rollout switch and the black terminal to ground. If I get 25.85 volts on the bottom terminal the rollout is good. If I do not get any voltage on the bottom terminal then the rollout has tripped and can be reset (if equipped) by pressing in on the little button or replaced. If your rollout switch is tripped you probably have a stopped up heat exchanger or a leaking heat exchanger. I would recommend calling in a service technician to find out why the rollout switch tripped. If you have an open limit control either the furnace has over heated or the limit has gone bad. Problems that would make a limit open up would be dirty filters, dirty evaporator coil causing a restriction in the air flow or a slow blower motor (check the capacitor on the blower motor to make sure it is good). A weak blower motor capacitor will cause the blower to run slow and eventually fail. Pressure switches, and limit switches can be tested with a meter in the same manner. With the furnace calling for heat you can test each of the terminals on the pressure switch to ground to make sure the pressure switch is closed. You should be getting between 24 to 28 volts from each terminal to ground if the pressure switch is closed. If the pressure switch is open you either have a stopped up vent, drain line (if you have a condensing furnace) or bad pressure switch.

Check all the ground connections from the circuit board and furnace cabinet. If continues, replace circuit board.

It might be the high limit, but it could also be the roll out switch or the flame sensor. Start by ohming out the simple switches the high limit the rollout if the are good use a piece of light grit sand paper or some emery and clean the flame sensor. This is a rod that sits in the flame of the burner telling the gas valve the burners are lite and it is okay to keep the valve open.

Sounds like two problems. Not enough combustion air or a defective high temperature limit switch. You enclosure may not be getting enough outside air to properly sustain combustion. If the unit has a rollout thermostat it may be defective and stopping everything.

ive seen this this year several times. first off take the combustion blowe loose from the ducting and look inside to see if theres any thing causing the blower to not run (water) what happens is that the flue gasses condense and run back into the blower then when it trys to start its binded.let me know if this does not solver the problem and we can get more into the furnance.