Hi Experts,

I have an old mechanical thermostatT834C - I'm trying to replace with a programmable Honeywell RTH111.

I have only 3 wires: R (Red), Y(Yellow), W(Green) - in my old thermostat.
I have connected Rh,Rc(Red), Y(Yellow), W(Green) - in new thermostat.

The Rh, Rc are jumpered. There is a HG setting for the fan, I have left as is.

When I turn on the system to A/C, the cooler seems to work, but I don't think the fan really works. The temperature does not cool and I see very little air coming from the vents.

How can I fix this, is it because there is no wire for the 'G' terminal?
I;ve tried both 'Auto' and 'On' modes, no luck.

Please help!

Vic

Old thermostat (pick the exact model number you have)

http://customer.honeywell.com/techlit/pdf/PackedLit/69-0434.pdf


New thermostat

http://customer.honeywell.com/techlit/pdf/69-0000s/69-2060EFS.pdf

Now you have all the information we have. Since we are not there you will have to use the drawings to figure out exactly what you have and how to hook it up to make it work.

Thanks, I jumpered Y to G, still didn't work.

Now I put back the Old thermostat on, but now that's not working either. I think the fan/blower doesn't come on, its not cooling. Also this morning when I went downstairs, I saw some ice/frost on the pipes coming out of the unit.

Have I got myself in to a mess trying to install a thermostat? And its about 97 today, 100 tomorrow forecast. Plleeeaaassseeee?

I believe you will be better served by ON SITE help under these circumstances. There are way to many possibilities and incorrect wiring can cause damage to the thermostat and the system.

NOW read this

The RTH111/RTH221 thermostats can be used to control:
• a gas, oil or electric furnace — 2 or 3 wires
• a central air conditioner — 2 or 3 wires
• a hot water system (steam or gravity) with or without pump — 2 wires
• a millivolt system — 2 wires
• a central heating system with air conditioning — 4 or 5 wiresNOTE: This thermostat is not compatible with heat pumps or
Multi-stage systems.

You only have 3 wires to start with so how do you think you are going to make this new thermostat work? It calls for 4 or 5.

I provided you with instructions for your new thermostat and this is on the first page under Introduction

No can you understand why it will not work?

I find it difficult to believe that the old thermostat worked with only 3 wires that is why I said you need ON SITE help because something is wrong with this picture.