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Charles Bodenheimer
Charles Bodenheimer, HVAC Mechanic
Category: HVAC
Satisfied Customers: 78
Experience:  Owner at BoMech Solutions
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I have a 4 ton Precedent roof top unit, Model YSC048E4HA1FD,

Customer Question

I have a 4 ton Precedent roof top unit, Model YSC048E4HA1FD, Serial###-##-####. Not heating. Immediately upon closing the disconnect at the unit, the burner inducer motor comes on and stays on. This is prior to the internet connected thermostat booting up so at the point the inducer motor comes on, there is no call for heat. I tried running it through the Test Mode by installing the jumper across LTB-Test 1 and LTB-Test 2 but the inducer motor immediately came on. I'm suspecting the ignition module is defective.
Thanks !
Bill Semanision
Neiman Marcus East Coast Distribution Center
Pittston, PA(###) ###-####email: ***@******.***
Submitted: 7 months ago.
Category: HVAC
Expert:  airheatman replied 7 months ago.

Bill does this one have a control board with an error light? And is igniter spark or hot surface?

Expert:  airheatman replied 7 months ago.

See legend below:

Customer: replied 7 months ago.
It does have a LED on the board and I have to check it when our weather improves somewhat. It is 5 degrees outside with a 20 mph wind. (the space that this RTU conditions is an interior space so it is not that critical)The ignitor is spark.Bill Semanision
Facility Engineering
The Neiman Marcus Group
East Coast Distribution Center*****Pittston, PA 18640(###) ###-#### (office)(###) ###-#### (mobile)
Expert:  airheatman replied 7 months ago.

Brrrrr.I understand that.Just come back to the question when it is warm enough for us to troubleshoot.

Customer: replied 6 months ago.
Finally able to get to the roof. There are two circuit boards. The left board is the ignitor board and that LED is flashing 5 times and the right board which is the main control board its LED is flashing 2 times. I have a photo of each board if that might help.
Expert:  airheatman replied 6 months ago.

If you are getting 5 flash code on ignition module.Turn power off and back on to reset board.If error still present replace board.It saying we have flame when we do not or should not.

Customer: replied 3 months ago.
I replaced the ignitor board as you directed. Unit fired up fine and ran for about 3 weeks then stopped running when calling for heat. Unit runs ok when calling for a/c. Finally got on the roof this week to troubleshoot (had 30 inches of snow on March 14, Stella the Blizzard). Everything fine with the control board. However, the LED on the ignitor board is flashing very rapidly, 10 - 12 flashes for a second(almost too fast to count accurately) then it repeats. This appears very abnormal. Could the new ignitor board gone bad? Did the power down and back on but same thing happens.
Thanks!
Bill Semanision
Expert:  Charles Bodenheimer replied 3 months ago.
Make sure all your Electical connections are good. Expecially all your grounds. Including the main ground. A flaky ground can cause all kinds of electrical issues with any digital control. Do that first and try to fire it again. If no luck make sure the hot surface igniter is pulling amps. What I do is have a volt meter clamped to the gas valve. I have alligator clips. At the same time have your amp clamp on one of the igniter leads. Look for amperage first and if you have it look for voltage going to your gas valve. If no voltage it's probably a bad ign board. If you have voltage it's a bad gas valve more than likely. But first. Make sure all the grounds are secure and Electical connections as well. This may indeed solve your issues. Hope this helps. Please Lmk your results so I can help you if needed. Lmk what your main power voltages are across the lines and each leg to ground. Good luck.
Expert:  Charles Bodenheimer replied 3 months ago.
Going offline. I will be back tomorrow. Give me all the details in the meantime. I'm sure I can help you. Check my profile. Thanks for using JustAnswer.Com!
Customer: replied 3 months ago.
When it calls for heat, nothing happens. The first steps in firing the burner is for the inducer blower motor to come on and do a prepurge, then it would fire. When the inducer blower motor come on normally, I would hear the click of the relay on the ignitor board, but don't get that. Again, nothing happens except for the LED on the ignitor board flashing very rapidly. Haven't gotten to the roof to check electrical connections and grounds. Tuesday will try to get up there.
Expert:  Charles Bodenheimer replied 3 months ago.
Ok. Lmk what you find. Thanks.
Customer: replied 3 months ago.
Checked all connections and grounds. All look secure. Ignition on this unit is spark. Turned power back on and it does the same thing.....nothing except the LED on the ignition board is very rapidly flashing for about 1 second then repeats. One note, there is a small (about an inch cube) transformer on the board that has discoloration on it as if burned (I looked at two other RTUs of similar size and the transformers on those boards don't have any of that discoloration). I'm leaning towards a bad control board.
Expert:  Charles Bodenheimer replied 3 months ago.
I agree. Go ahead and replace it to be safe. Lmk what happens. Thanks.
Customer: replied 3 months ago.
I replaced the ignitor board and it fired up without a problem. All is well. Thanks for the help !!
Expert:  Charles Bodenheimer replied 2 months ago.
No problem. Thanks for using justanswer.com.