View Full Version : Lennox L- Series
12-12-2005, 10:29 PM
another tech I work with was replacing heat exchanger on 15 ton rooftop when someone mentioned to him the blower runs all the time & will not shut off .. long story short he called me & i tryed talkin him through this because i am very familiar with L series controllers (26 individual units of this type i have accounts on, monthly PM + repair) .. but ended up showing up there .. its not the stat, not the controller, its not because of occupied, i even checked ecto settings & they are all ok .... at least im 99% sure .. ...system consists of one stat, no sensor .. all functions are normal but fan doesnt stop ... there is 24vac at contactor & i can pull it off at the boards output or contactor, which shuts it off... but unfortunately i cant live there & remove after every cycle ..unable to stay because of the company xmas party that night so we left & i am going back wednesday ....also it was 10 degrees outside so i know i wasnt 100% focused... i am going to check the quagmire of wires & make sure last company didnt rig the thing through the terminal strip(just got account) ..anyone with knowledge on these systems i would appreciate any ideas u may have .. i will find & resolve issue ... but maybe one of u has seen this b4 & can save me a little time
[Edited by gosteelers on 12-13-2005 at 07:17 AM]
Check the primary limit switch S10 and S99. If either limit trips the N.O. contacts will energize the K3 blower relay.
12-14-2005, 09:11 PM
thanks for your input ... now because of the cold that day & time issues i didnt thoroughly check everything but am sure the limit wasnt tripped, A. heat functions, B. no 50 code.... however i have seen instances where the N.O. side of switch had voltage at the same time as N.C. but i didnt check because again of no codes .. well because of the emergencies with the cold i havent made it back but when i do i will check that .. i appreciate your thoughts on the issue .. i will have more time the next visit to ohm all the switches & find any voltage drops not relating to this issue & clean them up .. this unit is older & needs a facelift anyway
12-17-2005, 12:25 PM
CDO you rule ... lol .... in less than 2 minutes i had my problem figured out & locating it was next.. i went right to the board & checked pin 111 # 3 & it had 24v ..I should have got it last time i am mad at myself lol..after pulling blower slide S10 ( as far as N.O. side )was ok as was S21 & S100... it was frikkan S99 & it didnt register as a signal loss because N.O. & N.C. were carrying signal ... i replaced S10 because it was in crappy shape & repaired a **** load of wiring .. this unit is on the ocean so **** is bad ... it had a very nice copper/copper evap though..all is good.. thanks & pat yourself on the shoulder for me
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