STC-1000 faulty heat contact

Has anyone had any problems with their STC-1000? I wired mine up, and discovered today the heat relay contact is faulty. The cool works fine. I can hear the relay cycle on heat, but it leaves the connection between the heat relay contacts open. Bummer. I have contacted the eBay seller. Fortunately I ordered two more of the units recently because I really like them so I should have a backup arriving soon.

Had the same thing happen last week it was just the cool side that did not work. The hot worked great. I contacted the seller and have a fresh one on the way. They covered return shipping and were very quick with communication. I'm glad I got it from NY and not China.

Thanks for the info. The seller responded by sending me a wiring diagram showing you have to put the hot to both the hot and cold relay separately, which I already knew that and had done it. I'll see what they say about getting a replacement.

Since I can hear the heat relay clicking, my guess is it is a bad or cracked solder joint on the board. Someone posted the circuit board pic in another thread, the thing looks pretty simple, so maybe I'll just see if that's what it is. Probably will take less time than trying to get a replacement shipped out, returning the old one, stuff like that.

I used a voltmeter and verified I had hot going in to both the heat and cool relay. The cool relay works fine, when it closes I get hot on the other contact. But not so with the heat contact.

Just to state the obvious, your not measuring the hot line when its in the compressor delay mode right?

Hm ... I don't think so, the light isn't flashing, the heat light is on at that time, and I can hear the relay click. I thought the compressor delay applied only to the cooling contact but I could be wrong.

porcupine73 said:

Thanks for the info. The seller responded by sending me a wiring diagram showing you have to put the hot to both the hot and cold relay separately, which I already knew that and had done it. I'll see what they say about getting a replacement.

Click to expand...

Hmm, why separately? I would think simply jumpering the hot from both hot posts would be the same thing as running a separate wire from the source.. or, am I misunderstanding what you are saying?.. which is very probable. I gotta see pictures/schematics

I mean separately as in running a hot wire to the heat relay contact, and a hot wire to the cold relay contact. Right, you could just jumper them together. Basically that is what I did, but I did not jumper anything using the terminals, because I had 12 ga stranded wire, which just barely you can fit one of into the terminals, much less two to be able to jumper at the terminals.

Here is the diagram the seller sent me (which would work, though she shows breaking the neutral rather than the hot which is not a good practice.)

The seller said she would send me a replacement relay to try. I assume she means just the relay and not a whole new unit. That's ok I guess, though it probably isn't worth the time it will take to repair it. I opened it up and the circuit board looks good, there are no broken solder joints or anything. So I'm assuming it's either the relay contact itself or possibly somehow a broken connection in the screw terminal. I suppose I could just break out to a SSR for the heat contact instead of replacing the relay.