Rheem Classic 90 Plus furnace


I have a Rheem Classic 90 Plus furnace. Lately it has been shutting down, normally at night and sometimes just switching the power off then back on is enough to get it going. At other times turning the power off and on will do nothing and then the furnace will start working again on its own several hours later. We had a technician in and he checked the furnace over and said because it was intermittent he couldn't do much, cost $60.00 When the problem next appeared it was a little different in that the burners would fire up for a couple of seconds then shut down, then fire up and shut down, then the flame light would flash on the control board. I cleaned the Remote Sensor and the spark ignition and sensor and it seemed to work for about 4 days before it shut down again. Now it just tries to cycle on (no Burn) and then shuts down, keeps trying to cycle on and at some point is successful as the furnace eventually starts and runs. The other evening it shut down and it was about 40 degrees when I got up, trying to recycle the power did nothing. We called a technician right away, but he showed up 5 hours later and by then the furnace had restarted. He checked the inlet and outlet pressures which were OK and he said the air inlet pipe was slanted downward going outside. He corrected this so now it is slanted up going outside. That cost me $110.00 and the following morning the furnace had once again shut down. Recycling the power switch got it going again. The inlet pipe is 4" PVC which has one 90 degree elbow and then reduces to 2 1/2" PVC going outside, total length is about 6 feet. The outside inlet pipe is horizontal with no 45 or 90 degree elbow. There is a moisture hose on the 4" PVC inlet and there is water in the trap. Could wind or snow blowing into this pipe cause the above problems? Any other suggestions, it is cold up here and local technical help is limited where we live?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@adga.ca wrote:

Hi, Most furnace retries 3 times before it goes into lock up mode. You can initialize logic board by powering on/off or it will reset itself to normal mode after 3 hours or so and try again. With my little bit of experience, it is usually inducer pressure switch or flame sensor causing that kind of symptom. Does your logic board give out trouble code by way of blinking LED? Once I had a problem on logic board. High Wattage resistor caused a cracked solder joint making the furnace intermittent. It is a simple sequential logic, to trouble-shoot logical sequence you need logical mind, LOL! If it reaches a ignition stage(flame on), next sequence is sensing the flame by sensor and then after some delay fan comes on. Trying new flame sensor may not be a bad idea. Also check loose wires/connectors I always keep spare ignitor and flame sensor. Good luck,
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Tony Hwang wrote:

If it was a consistent problem it would be easier to fix. The first time it went off for a long time, well over 3 hours and would not come back on by recycling the power. The next time it would reach ignition stage for a few seconds and then shut off then reach ignition again, then shut off and show a blinking Flame LED. This was when I cleaned the Flame sensor and the Ignitor and Sensor combination. This worked for a few days. Now, at least this morning, it would not get to the ignition phase until I reset the power. The furnace has worked well since this morning, but I am worried about tomorow morning. I understand the logical sequence, but this is not logical, it is random and that much harder to diagnose. This furnace is about 6 years old and all the wires/connectors seem fine and there is no noticeable cracking anywhere on the logic board. The technican supposedly checked the pressure switch and said it was working to specs. Any other suggestions?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@adga.ca wrote:

Hi, If logic board has cracked or cold soder joints by vibration of heat from big resistor, it's underside of the board.(opposite of component side)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.