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FMQ2-36 Electronics Module Blowing Fuse

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  • FMQ2-36 Electronics Module Blowing Fuse

    My FMQ 2-36 would not start. I only fill once a month. No lights on unit. Checked for 240v power and that was OK. Noticed the EM fuse was blown. Turned power to unit off at breaker and replaced fuse with same as original: T630mA L250v. Restored power via breaker and fuse blew. Purchased unit new 3/2012 through Parkway Chevrolet but did not get a response from them when I called.
    If anyone knows where I could get service from or any recommendations on how to proceed it would be appreciated.
    I am near The Woodlands, Texas which is in the Houston, Texas area.

  • #2
    This is a known problem, check the links. I had to replace the fuse block, the fuse blew not because of the load it was bad/lose connection in fuse block. If your handy with a soldiering iron you can replace the block with something off the shelf from local parts store

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    • #3
      Thanks for the reply. The fuse block is like new. No loose connections. One thread suggested this may be caused by the T282 power transistor in the EM board. Will try to locate that.

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      • #4
        Assuming you all are talking about a newer replaceable fuse holder. Check the end of the fuses for burn discoloration. If so dab the end of the fuse with a touch of di-electric grease. Good idea to pull the holder and use a touch of ei-electric grease on the spade terminals also. I use ABC 15 fuses that are available at the hardware stores. If blowing the fuse persists check the 4 wire block from the control module. 1-4 = 6.3 ohms (below 6 ohms is a bad or weak start winding) 2-4 = 2.7 ohms, 1-2 = 3.8 ohms. The #3 wire is ground and there should be no continuity to it from 1, 2 or 4. if the Q 2 tries to start but blows the fuse, chances are the compression module is seized.

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        • #5
          The 15 amp fuses are OK. They are the original in the original holders. No signs of burn discoloration. It's the 0.63 amp fuse that is blowing.

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          • #6
            Checked the resistance from the control module (four wires labeled "motor" on circuit board) 1-4 = 6.9 ohms, 2-4 = 2.8 ohms, 1-2 = 3.9 ohms. Looks good there. Disconnected all external wires from electronics board including capacitor wires, put in a new fuse and restored power. The 630 mA fuse blew indicating (to me) the problem is within the circuit board.

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            • #7
              If you or someone you know is an electronics service person, you can look for a likely ground of a component. If not it sounds like a new EM is due.

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              • #8
                I have an electronics engineer who is familiar with circuit boards coming this Saturday. After describing the issue and the response to a similar problem on another thread by slctech, the engineer said part availability will be the challenge. Have a call into NatG CNG Solutions for a replacement board as a backup.

                If anyone knows how to contact slctech please advise as he has indicated he has the parts and can also repair this problem. So far no response to my pm, to him.

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                • #9
                  Been there - had/have a few FMQ2-36 units (have not used them in 8 years since one seized and the other timed out again). As others have indicated, the fuse holder can get brittle from heat and need replaced, however, when your problems are not resolved by this usually there are two mains culprits listed below:

                  1. Motor capacitor - replace with a high quality one (I tried a cheap Chinese made one and it worked for about a month before the side blowing out on the cap and had to get a GE one made in Mexico).

                  2. Transistor and Resister change on main board - can't remember the details but there is a a couple components that degrade. On mine one of the resistors discolored from heat when the transistor failed. I once had the schematic but have no idea what I did with it. When I ordered replacements I got a couple extras but looked and can't find today.

                  If your friend is an Electrical Engineer, try to get the schematic for him/her so he/she can probe the circuit. Might want to have a descent multi-meter handy (& extra fuses) as well. I got tired of working on these units and went public station after many repairs. Note: my units are over 25 years old and I did not want to spend the money to get new or rebuilt compressor modules.

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                  • #10
                    One other thought - it was not difficult to get the replacement parts (not too specialized) and the main board is through hole technology.. Found the transistor & resistor on Mouser (Digi-Key also had) and got the capacitor on ebay. Full disclosure: This was 10 years ago.

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