Trane rooftop w/Relia Tel won't C1

[allstar08]

Trane unit cooling only w/ econ.

MN: TSC092A4R0A0TD
SN: 253100021L

has RTOM

I cannot get 1st stage cooling to fire in test mode and only C2 comes on when the unit goes into cooling. I unplugged J4 on RTRM to eliminate all optional boards, but it still won't fire off in test mode. It doesn't have the LON card. I have verified 24 volts on the LPC return at the board and I can put 24vac to the out put on the board and it will fire, but not at any other time.

The question is am I missing anything? I am leaning to a new circuit board, but since I don't work on these things everyday I thought you guys might have some advice.

[mesahvac]

hey allstar i would try swapping the rtrm board with another unit at location if any that are same. I had a similar problem a couple times one time it was a defective options module figured out by isolating boards. Another was unit had been programed for single stage operation so unit would only turn on one stage even in test mode. best of luck

[allstar08]

This unit has worked before, so the programming thing doesn't make sense. Man, I wish there was another board on this roof, the only other unit is an Intelpack.

[Airmechanical]

Trane unit cooling only w/ econ.

MN: TSC092A4R0A0TD
SN: 253100021L

has RTOM

I cannot get 1st stage cooling to fire in test mode and only C2 comes on when the unit goes into cooling. I unplugged J4 on RTRM to eliminate all optional boards, but it still won't fire off in test mode. It doesn't have the LON card. I have verified 24 volts on the LPC return at the board and I can put 24vac to the out put on the board and it will fire, but not at any other time.

The question is am I missing anything? I am leaning to a new circuit board, but since I don't work on these things everyday I thought you guys might have some advice.


when you tested it, was it with the test pins 1 and 2 on the unit itself

or were you testing your controls



.

[nytrane]

Might be a dumb question but did you put gauges on this circuit.

[allstar08]

when you tested it, was it with the test pins 1 and 2 on the unit itself

or were you testing your controls



.

I was checking it @ the units test pins

[allstar08]

Might be a dumb question but did you put gauges on this circuit.

I checked continuity on all pressure switches, as well as the 24vac input from the LPC on the circuit board.

[novato1]

allstar,
Make sure that on the test board you have all the proper jumpers in place....if one is removed it will go into test mode and it will lock a circuit out. i had such problem during a start up of a unit. Check the schematics....if I recall it will tell you where the factory jumper should be. Hope it helps.
http://i1027.photobucket.com/albums/y331/gman1975/TESTBOARD.jpg?t=1271631602

[lihvac54]

Funny question....Is this unit T-Stat controlled or BMS controlled....If it is BMS controlled(Tracer Summit/Tracker etc.) and has a comm card, disconnect the comm card and isolate the unit. Its very possible someone made a boo boo and disabled circuit 1 through BMS. Regardless of normal operation or Test Mode, a function will not operate if disabled through the configuration menu.

[allstar08]

allstar,
Make sure that on the test board you have all the proper jumpers in place....if one is removed it will go into test mode and it will lock a circuit out. i had such problem during a start up of a unit. Check the schematics....if I recall it will tell you where the factory jumper should be. Hope it helps.
http://i1027.photobucket.com/albums/y331/gman1975/TESTBOARD.jpg?t=1271631602

checked it before the jumper is in place

[allstar08]

Funny question....Is this unit T-Stat controlled or BMS controlled....If it is BMS controlled(Tracer Summit/Tracker etc.) and has a comm card, disconnect the comm card and isolate the unit. Its very possible someone made a boo boo and disabled circuit 1 through BMS. Regardless of normal operation or Test Mode, a function will not operate if disabled through the configuration menu.

stand alone, no such luck

[brooklyntech]

Heres an even dumber question. Have u checked ur compressor contactor coil? Sounds like u have an open coil. If that doesnt work, check ur wiring going back to ur economizer board/actuator. U migh have a wire loose, rubbing out, or disconnected.

[allstar08]

Heres an even dumber question. Have u checked ur compressor contactor coil? Sounds like u have an open coil. If that doesnt work, check ur wiring going back to ur economizer board/actuator. U migh have a wire loose, rubbing out, or disconnected.

I can jump 24vac on the circuit board and it will fire.

[brooklyntech]

OK, then it might be time for new board.

[monstercourier]

:couch: Please keep us posted. I have had the same EXACT issue. Went through it with Trane's light commercial tech support and they couldn't give me an answer. I changed the board as suggested and still..................no luck. Tech support had me disable the economizer, options, and ignition modules which he claims could cause a similar issue. My unit was a heat pump, and it acted as if circuit 1 didn't exist. It would completely skip over all of the circuit 1 test functions. Definitely logic related, not safeties or contactors.
To this day 1 year later, the customer luckily has not complained about it. By the way if it matters this unit is on a Trane stat not sure about yours.

[bm92g7]

I had a similar problem and turns out that the board was sending 24v to both sides of the C1 coil. When I would test each side of the coil to ground I would get 24v so it wouldn't pull in obviously. There was an identical unit next to it, swapped boards and it worked out, ordered a new board, installed it and it runs like a top now.

[whiteside2831]

Have you checked the reading of the OAT? Ive had several sensors fail and hold out the first stage. Disconnect the sensor and it reads a default 74. I had a bunch reading -10 outside when it was in the 90's. I have a Trane manual with all the sensor readings in my van. You can email me if needed and tell me what the DCV readings are and I can tell you if its within range.

[jpsmith1cm]

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