Blower Cuts Out In Cooling

[valdelocc]

the smoke detector should be breaking R, not just G

if you been at it for some time, you probably would had see it configured in more than one way.
I bet a six pack there a bad duct detector in that unit.

[beenthere]

if you been at it for some time, you probably would had see it configured in more than one way.
I bet a six pack there a bad duct detector in that unit.

Good possibility.

[timebuilder]

I think hes talking about a smoke detector, thats would kill the blower when tripped.

(Maxwell Smart voice)

"Ah, the old economizer smoke detector trick!"

[VTP99]

nope mechanical cooling control interlocked with fan contractor, very simple stuff! sooner or later you'd run into one.

Could you get a model number on one of these units ?
I would like to pull up the wiring diagram.
Thanks,
VTP

[timebuilder]

I've seen the need for a G signal on the older York units. I'm eager to find out which Carrier units need it, too.

[VTP99]

[flanders]

I think hes talking about a smoke detector, thats would kill the blower when tripped.

You are correct. I took it out and cleaned it up. It's a smoke detector. It was covered with about 1/4" of dust. So far it hasn't tripped again. Thanks to everyone for their help!

[madhat]

We have RTUs with the board on the relay, the back side of the board the male push on terminal solder connection breaks. Sometimes just pulling the cover off will start / stop the fan. A little flux on the terminal, bit of solder on solder iron tip, and just touch the solder connection, as soon as it melts pull off. Do all of them as you can't see which one is broken. Don't forget to clean the flux off!!

[flanders]

It ended being the in-duct smoke detector. It cuts out the blower when tripped. I will keep your advice in mind on the next time it happens. Thanks for the input.

[rpkilgor]

Consulting the schematic would have made troubleshooting this issue easier. No voltage at contactor coil... find the contactor coil on the schematic and check for voltage on each point you trace on the schematic all the way back to the contactor. There should be nothing mysterious about how a unit operates if a good schematic is available.

When you work on larger equipment or unfamiliar equipment, a good schematic is priceless. You may have a huge control section full of components you don't recognize and over a hundred terminals. Without a schematic, diagnosing a problem as simple as a bad relay could take many hours. With a schematic, and you've got it figured out with 5-10 checks with your multimeter.

[flanders]

The smoke detector wasn't on the schematic.

[timebuilder]

The smoke detector wasn't on the schematic.

Thats true. Very often, a smoke detector wont be on the schematic.

However, if you start following the circuit ON the schematic, you will quickly find where you lose the power, which in this case is the smoke detector.

[VTP99]

Had two out of three units down last week for the same reason. All three units wired together. Unit one was OK but unit two cutout number two and number three.