|
|
Elite Veteran
  
Location: Medford, OR | So it's over a 100 degrees here now....Why not work on AC's and see why they don't turn on? Well, both units circulating fans have always worked, but no compressor or condenser fan has ever turned on. So I dragged the first AC out and found that I wasn't getting 110v to the cooling system. So I opened up the control panel inside above the closet, and found some funky PO wiring coming out of the thermostats? This wiring coming out of the thermostats goes to/through an 8-pin relay (one for each unit) that is hanging inside the closet (I always wondered what this wiring/relays was for inside the closet?) The wiring comes out of the relay and back into the control panel and ties back into the cooling circuit. I fiddled with the relays and plugs and was able to get both AC's to fire up! Wiring is my huge weak point, so why did someone wire in these relays? I took one of the thermostats out, and put a meter on it, found that nothing was happening. Both the factory Duo-Therm thermostats are toast. I by-passed the thermostats and relays and both AC units run and cool great. What should I do here? Purchase replacement thermostats (if I can find)? Try and clean up the aftermarket relays and wiring (relays are about 30 bucks with shipping)?? Or just run the units with the thermostats by-passed? I won't be running the AC's that much, so I don't think coil freeze up will be an issue. I hope what I wrote here makes sense to someone. I posted a couple pics of the relays I found in my album.
Dan #850
Edited by dkarnath 2016-06-06 9:28 AM
|
|
| |
|
Contributor
Location: Salem, Or | Someone let the smoke out, Dan! Circuits just won't work unless the smoke is well contained. Seriously though, the evidence is there (burned wires) that the relay and associated wires were attempting to start and/or operate a load beyond the wires current carrying capacity. Also, it's remotely possible that PO shorted the load wire from the relay directly to ground. Would advise to review the FMC diagram, the AC diagram and the PO's relay schematic (follow the wires and sketch accordingly) to get a clue about what his plan may have been. Best approach is to get back to the manufacturers circuit plan. Not much help for me to just state the obvious from the pictures but PO mods are sometimes really difficult to understand.
Harry #400 |
|
| |
|
Elite Veteran
Location: Medford, OR | The PO relay system is not going back into service. I found Duo-therm manual thermostats on line, anywhere between 22-40 bucks. I think I will go that route soon. Maybe someone can give me an idea on where the temp probe goes....Not sure how accurate the thermostat would be with the temp probe inside the control box.
Another idea that may play a part in this add on relay situation, is the PO added a 110v outlet inside the closet (for a wall mount tv), he pulled power from the AC junction box in the rear of the closet. If you were watching tv, and the AC's kicked on, would you get an interference/power surge on the tv?? Just my electrical non genius head thinking here..... |
|
| |
|
Elite Veteran
Location: Medford, OR | So I tested one of the thermostats, it works fine, I'm sure the other one will be good too. It's a Klixon brand switch. I posted a couple pics on my album. They are not the factory Duo-Therm 3-10730. Where I'm stumped is....Don't I need a transformer to reduce voltage to the thermostat? The factory wiring shows the brown wire coming out of the fan rotary switch going directly to the thermostat (I posted a pic). Maybe the PO put these Klixon switches in and this why I have the 8-pin 110v controlled relays wired into the thermostat loop to reduce the voltage back to the thermostats? I don't see a transformer on the factory FMC schematics? Is the factory Duo-Therm switch a 110v controlled style thermostat? I don't think I can wire this Klixon switch according to the factory wiring diagram, it would burn up I suppose. I see my "electrical adviser" tonight to look over the schematics, maybe he will have an idea of how (what I need to buy) in order to put it back to stock. |
|
| |
|
Elite Veteran
Location: Medford, OR | I need a couple of Duo-Therm 110v thermostats....On the prowl now. If someone has a couple, let me know, I will buy. |
|
| |
|
Elite Veteran
Location: Medford, OR | Found a direct replacement on ebay...I will post part numbers after I install and confirm part is correct. |
|
| |
|
Contributor
| Hey Guys, Bob Comp here, coach #639, I have been toying with this thermostat issue for a while and this is what I have found. First of all, I work on air conditioning at my job and have been an electronics tech all my adult life. What I have found is the clixon type thermostats and no relay box in the closet that I know of. When I get time, I will look at the schematics and see if the relays are factory installed. The clixons are inferior for the purpose because they are inside the control panel and they are controlled by bimetallic strips (the sensor and actuator). They are isolated from the air flow and in a poor position to sense room temp. Good thermostats have sensing bulbs located in the area that you want to control (often sensing inlet air to the ac). I replaced mine with an industrial thermostat that has 2 switch circuits so it will handle both ac units but it is in the hallway and does not sense as well as I would like. Also, watch the wire size that you use because this circuit passes about 15 A. That may be why the relays were added when PO changed the thermostats. You can use electronic thermostats with a 24 volt transformer and relays or just a mechanical thermostat as long as it will handle 15 A. I am going to try 2 line voltage thermostats located in the areas where they will not directly affected by cold draft from the ac, just remember 15 A line current. Simple line voltage thermostats are usually used for electric baseboard heaters, they use bimetallic strips for temp sensing and control, mount on a rectangular wall box, handle lots of current and aren't too expensive. |
|
| |
|
Elite Veteran
Location: Medford, OR | You have the same Klixon thermostats I have. The relays associated with the klixon's are not factory. This must of been a common fix for bad factory thermostats? |
|
| |
|
Contributor
| My workweek is finally over and I have time to look at the schematics, it is as I remembered it, a very simple circuit. No relays between the AC units and the remote control box above the closet. It advises 12 ga wire to any remote location up to 25 ft, The circuit is 115v 15a per ac, no relays in between and those odd thermostats isolated in the control box. Again my suggestion is a line voltage thermostat located in a good spot, one for front and one for back and leave the 6 position selector switches above the closet. Bob |
|
| |
|
Elite Veteran
Location: Medford, OR | All the quality "cooling line voltage thermostats" I see on the web, are priced only a few dollars cheaper than the factory thermostats. Anywhere from 35.00-50.00 dollars |
|
| |
|
Contributor
| Hi, Bob here, I just did a quick search on ebay and found line voltage thermostat's from about 30.00 up to 100.00 . If you use the factory stats then I assume you will mount them back in the control box where they won't sense temp well. My idea is to mount them away from the air draft so they sense ambient temp without much draft from the ac. What I have observed is if I run the front ac the back is still hot and if I run only the rear ac is hot. Even my industrial thermostat which is mounted next to the control panel above the closet and has a sensor coil on top of it and controls both ac's (2 stage) does now work right unless I have a small fan circulating air through the hall. That is why I want 2 separate stats located front and back. Hopefully this will help you make a choice, remember, 115v 15 a across the contacts of the thermostat. Bob |
|
| |
|
Contributor
| Well, here we go, too many beers and not enough proof read. What I meant to say was if I run only the rear ac then the front area is hot and my industrial stat which is mounted in the hall does not work right unless I use a circulator fan so it is best to have 2 stats, 1 front and 1back. Bob |
|
| |
Duo-Therm AC thermostat issue? Electrical goorus help?
