Original message
| philso
 |  "carrier 58STA gas furnace not starting up"
, posted Sun 2 Nov 15:06  
Hello
I have a Carrier 58STA070-12 gas furnace that will not start up properly. It was installed in the spring of 2005 and was working properly at the end of the last heating season. When heat is called for, the relays on the control board click on and off, continuously, with on and off times of about a second or two. Please let me know what I should check next.
The Induced Draft Blower motor turns. It seems to only get voltage part of the time. The reading on my meter fluctuates wildy as the relays click on and off. Evenually, the IDB "gets up to speed" and the pressure sensor switch closes.
The Hot Surface Igniter never seems to get voltage for any sustained period of time and I never see it glow. My meter readings go from near zero to about one volt when the relays start clicking. I have disconnected the HSI and measured a resistance of 50 Ohms. This seems to be in the range that people indicate as normal.
I have checked the voltage across the string of four interlock switches and they seem to remain closed all the time.
I have checked the various things that I have seen posted on this forum. The red LED stays on constantly and does not flash through this.
I have checked the gas cut-off valve and it appears to be on. Our gas hot water heater is working fine. There is no smell of gas anywhere. The thermostat is able to command the air conditioner to turn on and cool.
We did sustain some light damage to our roof shingles when Huricane Ike blew through.
Thanks for your help.
Phil
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Replies:
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| murphcoair
| "Re(1):carrier 58STA gas furnace not starting " , posted Sat 8 Nov 20:00
It is normal for the indoor fan to run for 90-120 seconds when you provide 115 volts to the furnace while r to w is jumped or the stat is already calling for heat. The L.E.D should display a code 12 during this power up sequence. After the delay the furnace should start its normal sequence of operation. If not then on to the next step.
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| murphcoair
| "Re(1):carrier 58STA gas furnace not starting" , posted Sat 8 Nov 19:55:
It is normal for the indoor fan to run for 90-120 seconds when power is restored to the furnace when r to w is jumped or the thermostat is calling for heat, during this power up mode the L.E.D will disply a code 12 ( blower on after power up). After the delay the furnace will resume its normal sequence of operation if no other problems exist. If not on to the next step.
[this message was edited by murphcoair on Sat 8 Nov 20:06] |
| | philso
| "Re(2):carrier 58STA gas furnace not starting" , posted Mon 10 Nov 01:31
Hello Murph and Yuri
Thanks for the tip about the 90-120 seconds of main blower upon restoration of power.
I disconnected the thermostat, jumpered R to W and turned the power back on. The Main Blower came on immediately. After about 110-120 seconds, the Induced Draft Blower came on and stayed on. After about another 20-20 seconds, the Hot Surface Igniter started to glow. Another 10 seconds or so later, the Gas Valve clicked and the Burners turned on. A few more seconds later, the HSI turned off. It looks like my furnace is OK.
I re-installed the thermostat and put my meter on the the W and Common terminals on the control board. The voltage is just at 24 Vac with less than a quarter volt of fluctuation. I suspect that the fluctuation is due to a bad output relay on the thermostat that is "chattering" adn causing glitches on the signal comanding heat. Unfortunately, a meter is not very good for picking up fast glitches. The voltage on the R terminal is up around 27 V with even less fluctuation. I had changed the batteries before with no improvement and it didn't help today.
I will try a new Honeywell thermostat as per Yuri's suggestion.
Thank you both for your assistance.
Take care.
Phil
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| | philso
| "Re(3):carrier 58STA gas furnace not starting" , posted Mon 10 Nov 23:38
Well, I borrowed an oscilloscope from work and looked at the R, W and G wires. The R has a steady, clean looking sine-wave that the scope measures at 28.2 Vrms.
When the thermostat calls for heat, the W wire has a sine wave with chunks missing out of it. the scope measures this at 24.4 Vrms. The peaks are the same amplitude as the signal on the R wire. The relays on the control board click on and off. When the thermostat is not calling for heat, the W wire has some kind of funky, distorted sine wave on it that is maybe a volt or two. If I remove the thermostat and jumper R to W, the heater goes through it's start-up cycle properly and the W wire has the proper size and waveform on it.
When the thermostat is calling for cooling, the G wire has a clean looking sine wave the same size as that on R. When the thermostat is not calling for cooling, the G wire has a flat line zero Volts on it. I also noticed that the thermostat does not allways call for cooling when it should.
I think this confirms that it is my thermostat that is flaky. I will order one of the Honeywell FocusPro's tomorrow.
Thanks again, gentlemen.
Phil
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| yuri
| "Re(1):carrier 58STA gas furnace not starting" , posted Sun 2 Nov 15:57:
What type of thermostat do you have. It may be sending a fluctuating 24 volts to the board. You should have a steady 24 volts from W to C on the board when calling for heat. The el cheapo or older electronic tstats can act up and do that and damage the board. Check for 24 volts between R and C when idle. If not there then a power surge damaged your transformer. Check for 110-120 volts coming into the furnace. I recommend the Honeywell Vision or Focus Pro thermostats. Start with the tstat/ and put new batteries in it. You can also remove and LABEL the wires from the tstat at the board. Put a #18 wire jumper between R and W. Turn on power and see if it works. Move to Canada, our hurricanes are white and we call them blizzards.
Yuri
[this message was edited by yuri on Sun 2 Nov 16:03] |
| | philso
| "Re(2):carrier 58STA gas furnace not starting" , posted Sun 2 Nov 23:54
Hello Yuri
Thanks for the suggestion.
I get a constant 27.75 V between R and C at idle and when calling for heat. I get a constant 24 V between W and C when calling for heat. I am using a RiteTemp thermostat from Home Depot. I unplugged the thermostat from it's base and jumpered R to W. There was only one click as the main blower came on. The LED flashed a code indicating that the blower was on. Nothing else happened. The IDB did not seem to want to try turning on and I did not see the HSI glow. I left it for about a minute then shot the power off, removed the jumper and re-installed the thermostat. Do you have any other suggestions?
Oh, yes, I know all about blizzards. I had lived in Ottawa for 4 1/2 years and in Toronto for about 12 years. I will probably move back to Vancouver (or Vancouver Island) when I retire.
Thanks again.
Phil
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| | yuri
| "Re(3):carrier 58STA gas furnace not starting" , posted Mon 3 Nov 22:24:
Sounds like your circuit board is faulty. Should not do anything other than start the inducer fan when you jumper r to w. Should not start the blower unless the tstat is configured for electric heat. Try jumper r to w at the board instead. You may have some shorted/bad wiring between the tstat and the furnace. Rare but it happens. Carrier has had lots of problems with those boards and you may have had a power surge which damaged it. I don't like Ritetemp, Hunter, Lux or any other than the Honeywells. Had too many servicecalls problems with them.
Yuri
[this message was edited by yuri on Mon 3 Nov 22:27] |
| | philso
| "Re(4):carrier 58STA gas furnace not starting" , posted Sat 8 Nov 18:04
Hello Yuri
I disconnected the thermostat wires from the control board and jumpered R to W as you had suggested. I still get only the main blower turning on when I re-apply power.
With the thermostat wires connected, the IDB still tries to run, but never really gets going. The HSI never comes on.
If I disconnect the wires to the IDB and apply 110V directly to it, the blower comes on strong. The voltage across the pressure switch drops from 24V to less than 1V a second or two after I apply 110V to the IDB. The HSI still does not come on.
With the IDB connected normally and the HSI dissconnected from the control board, I applied 110V directly to the HSI. It started to glow orange/yellow within a second or so.
I have found a few places on-line selling the control board for well over $200. We are still within the 5 year warrantee (for parts only). would it be better to have the original installer come out and replace it and just pay the labor?
Thanks.
Phil
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