Trane RTU Test Mode

[HVAC_Austin]

Hello everyone,

Earlier today I was trying to get a Trane RTU to start in test mode. Simple enough, just jump LTB 1 and LTB 2 and sit back and wait. The only problem is that it just got stuck in step 1 (the blower or something--can't recall) for 10 or 15 minutes before I gave up. The compressors never energized. I tried the test in two different ways:

1) Turn power off, put jumpers on, turn power back on and wait for test mode to start
2) Turn power off, turn power back on, then put jumpers on and wait for test mode

Neither way seemed to knock any sense into the thing. I got it to work on two other Trane units earlier in the day, maybe I was just tired Am I missing something?

[alcomech]

Is this a Microtel control board

[HVAC_Austin]

Is this a Microtel control board

To tell you the truth, I don't remember. I looked at so many of these things today my head is still spinning. What would it mean if it were a Microtel?

[alcomech]

There are two type of boards. Microtel or the new Reliatel board.
If you are trying to test from the LTB test 1 & 2, you will need to verify that the wire plug is connected to the board.

You really should be using a decade box for variable resistance testing.

What is the Model No. and Serial No.

[HVAC_Austin]

What is the Model No. and Serial No.

Sorry, I don't have the model and serial on me. But I will check to see that it's plugged into the board. I only recently began doing PMs on my own, so I'm fairly new at this. Why would the plug be disconnected?

[chillerout1]

f its not reliatel it is not ltb1 & 2 it is test 1&2 two different sets of terminals on low voltage terminal board

[tech56]

correct me if i am wrong but if i remember correctly, to use test mode without resistors, you need to jumper the terminals for one second and then remove jumper. to move to next test function jump T1 & T2 again for one second so on and so forth. hope this helps!

[alcomech]

Sorry, I don't have the model and serial on me. But I will check to see that it's plugged into the board. I only recently began doing PMs on my own, so I'm fairly new at this. Why would the plug be disconnected?

There are times when some feel that it is easier to test directly from the board. I disagree with that method.

[alcomech]

correct me if i am wrong but if i remember correctly, to use test mode without resistors, you need to jumper the terminals for one second and then remove jumper. to move to next test function jump T1 & T2 again for one second so on and so forth. hope this helps!

As the OP has stated he has ran this unit in test mode for 15 minutes and has clearly lost his position. In this case there is no other or better method than to use a decade box. But if he does not have one than he can simply purchase a resistor as stated in the troubleshooting manual and test the mode which is of concern.

Otherwise he will need to be certain that he has tapped the terminals and follow the sequence so that he will be in the correct mode. Even for a very experienced tech and when experiencing erratic behavior it is difficult to follow the modes......nothing beats a decade box.

[jayguy]

...nothing beats a decade box.

absolutely!

test mode only works if there isn't a problem mechanically. perhaps you have an open low pressure switch or other safety.

[tech56]

Yes I know that but the way the OP was written it sounded like he put the jumper between t1&t2 and left it in place. Maybe I read it wrong.

[Sp4wN26]

correct me if i am wrong but if i remember correctly, to use test mode without resistors, you need to jumper the terminals for one second and then remove jumper. to move to next test function jump T1 & T2 again for one second so on and so forth. hope this helps!

Absolutely right! test mode on trane RTU goes from fan to econo, compr1, compr2, heating etc.

It was also my understanding as I read that you said you jump tb1 and tb2 and sit back instead of jumping them for only a second or two!!

[Zeke XI]

With jumper left in place unit will change steps every 30 seconds. For those without patience (like myself) take the jumper off for a five count then back on for five to get to the step you want. Will not go to a step with a safety open (limit/switch). Should also see the RTRM or UPC light flashing which indicates unit is in test mode.