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Carrier furnace problem

tinhuynh17
tinhuynh17 Member Posts: 2
Hi guys,

I have an old carrier furnace unit from 1994 (58RAV095-13116) that is currently not functional. During troubleshooting I got the unit to glow but then it shut off within 3 seconds. I tested the voltage coming into the gas valve and it keeps reading 18V even when I have the safety switch unpressed. I feel like it’s a bad control board (maybe issue with the relay where it stays partially open somehow?).  Just wanted to get you guys’ thoughts on this. 

Thank you in advance for your inputs!

Comments

  • 109A_5
    109A_5 Member Posts: 1,377
    Hello @tinhuynh17,
    Is there at least 24 VAC at the secondary of the transformer ? Since the path between the transformer's secondary and the Gas valve has many connections and Safety Limit devices I would find out where the missing 6 VAC is before I randomly changed anything. Relay contacts GVR-1 may be the problem, if so the missing 6 VAC would be across PL1-2 and PL1-3. Could be a poor solder connection at the relay GVR-1 or a pin of PL1. Also I would re-seat connector PL1.

    Is the LED flashing an error code ? See manual if you don't have one.
    http://www.alltemp-hvac.com/58p,r-15sm.pdf



    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • tinhuynh17
    tinhuynh17 Member Posts: 2
    Hi @109A_5. There is 24V coming out of the transformer. The error code was 21. Hmmm is there an easy way to check the voltage accross the relays without having to drop the board? Wanted to see if there is a solution before I start disconnecting the vent pipe and such. Thank you so much btw for the idea!
  • 109A_5
    109A_5 Member Posts: 1,377
    Hello @tinhuynh17,
    Some folks use T-Pins to 'Back Probe' the connector PL1 sliding the T-Pin between the connector body and the wire until it just touches the connector pin. I have used 0.030" MIG welding wire too. Also a set of clip leads makes it an easier and hands free measurement.

    You can follow the wires away from the connector PL1 and measure at the device the wires lead to (Red arrows). Keep in mind the farther away you get from the device or the relay contacts you are interested in the more places a bad connection could be and not be the device or contacts you are focused on.

    Usually I pick the test point of easiest access, since if the problem is not there you can just move on. If it is there you can focus deeper. Often splitting the circuit in half (divide and conquer) will focus you to the defect fast. Since your meter can't be in two places at once make sure you know when the power is supplied to the circuit so you don't get a false negative test.

    To see an abnormal Voltage drop at the Relay contacts GVR-1 you could measure at GV GAS VALVE (PL1-3 Blue Wire) and at DSS DRAFT SAFEGUARD SWITCH (PL1-3 Orange Wire). Keep in mind the PL1 connections and the PL1 and Relay GVR-1 circuit board solder joints are now included in the test, not just the Relay GVR-1 contacts.




    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • HomerJSmith
    HomerJSmith Member Posts: 2,426
    edited November 2022
    I would look at the relay solder connections on the back of the board to see if there are breaks in the soldered connection. This is a common failure in these boards. If there is a break in the joint you can resolder the joint with resin core solder.
    109A_5