Roof Top Unit

[UnknownSoldier]

I am working on a York RTU, The relay in the circuit board chatters and causes the contactor for the blower to chatter. I replaced the circuit board thinking it was a bad relay in the board. Same problem, i switched out the transformer, same problem. Anyone have any ideas..

[yellowirenut]

plenty...but would like to know more about you first.

remember no DIY on this site

[UnknownSoldier]

I live in Buffalo NY, I work at the largest GM Dealership in the north east. I have been doing residential and commercial repairs and installations now for over 13 years. I have my universal HVAC/R license. I used to own my own business, but the economy has made me seek other means of income. The unit I am refering to is approx 14 yrs old. I have made several repairs on these units, we have 7 of them, but this is the first time I have encountered this problem. I have jumped out the t-stat, replaced the transformer and the circuit board, I tried disconnecting the blower contactor and the lead that goes into the limit switch. I get a constant 26 volts but i dont know why the relay in the circuit board is chattering. Any help would be greatly apperciated.

[phbsales]

Too many loads in series?

[UnknownSoldier]

It's all factory, I was thinking the transformer was week, I replaced it, Still has the problem. I have 5 other unit of this model all same year, all wired exactly the same. When I disconnected the blower contactor and the lead to the roll out switch, it would have corrected the problem if there were too many things in the series, Those are the only 2 things that run off of that relay.

[yellowirenut]

ohm out the circuit something is not making full contact...you answered that yourself and have not notice.

[mpflood]

Try putting blower delay timer from another unit in problem unit and thank me later.been there,done that.

[kevincompass]

its the bord had the same problem the other day put a new bord in and cut the old relay apart it was all pitted its an issiue with york bords

[timebuilder]

I work on these units frequently and have not seen this issue. It sounds as if you have a current drain or a high resistance somewhere.

The board issue I see is people pressing too hard on the terminal strip and loosening the circuit traces on the back of the board.

Get 15 posts and apply for pro membership.

[redwhitekat]

i would start at the blower, make sure the motor/ cap is all ok, then i would look at the blower delay im assumig its a double stack, christmas tree timer, then inspect the wiring, another way is disconect the blower (load) and see if it still chatters

[Octopus]

I have had that exact particular issue and 90% of the time was due to a bad contractor coil. The other 10% eh could be anything, bad limit, switch, t-stat or wire. wire rub, anything along those lines.

-good luck, hope this helps

Ps, Some patients, a good multi meter and a little luck along with your skills will get you to that AH HA moment.

[Paul Bee]

Single phase or 3 phase? Start at the source! I can't tell you how many times a weird electrical problem turned out to be a charred fuse passing partial voltage or a wiring issue. Did you do a voltage test on all hot lines and compare that to another unit on the roof? Let us know what you find.