I have a Trane made in 1986 model BWC036C100CA

Only when it is cold around 40 degree outside the big coil freezes up and I get no heat. A/c and heat unit is up on roof, one unit. Im in phoenix, az.

Maybe defrost is not working or bad board/relay not sure.

Please advise

Thanks

Maybe defrost is not working or bad board/relay not sure

Could be the defrost board or a low refrigerant charge. If the A/C worked OK in the summer then I do not think the unit is low on refrigerant.

Have you tried the emergency heat mode?

My thermostat doesn't have emergency heat mode on it. It is a older unit.

Also the a/c did work pretty well during the summer and it does get pretty hot here.

BUT during the summer when it is really hot outside above 110 the house will not get cooler than 83 degree's, the a/c unit can't keep up. It use to be a little better than that, cool the house down to around 79.

From the summer temp statement the unit seems to run fine. I believe you will find your problem in the defrost circuit.

I wonder what the defrost circuit consist of? Defrost board, relay? I need to find the diagram of the a/c heat unit layout.

Look one the blower access or burner access door for diagram.

83 is very good for any a/c I`ve ever seen, shouldn`t be any complaints there, guess refrigerant is OK,,

outside above 110 the house will not get cooler than 83 degree's

Yes the A/C is doing great look at the TD between inside and outside.

110 - 83 = 27. Gee... if I go "south" when I die, one of those would come in handy...

Well I should say 110-118 degree outside inside is 83. I know other peoples houses get colder than mine in the summer though. But really my problem is with the heater right now, coil freezing when it gets below 40 degree .


I will look for diagram or call trane factory to get info.

Check the control compartment at the outdoor unit for a literature packet. Trane is usually really good at providing info, but not so good at keeping it dry.

Quote:

---

Originally Posted by KC13

Check the control compartment at the outdoor unit for a literature packet. Trane is usually really good at providing info, but not so good at keeping it dry.

---

Or at making parts readily available :mad:

The paper diagram is toast, all weathered can't read and falling apart.

Will have to find other means

Sometimes there are two, one inside and one outside the control compartment... did you look inside too?

The one inside was the one that is toast. Didn't see another

Say... I just had a service call last week, similar model and almost the same age. The defrost control would stop the outdoor fan but wouldn't power the reversing circuit or auxiliary heat. Try this: with unit running, locate the test terminals on the defrost control and initiate a forced defrost. See if the unit reverses to cooling and stops outdoor fan. Be careful of live electricity!

How is the proper way to force defrost mode? I am handy.

There are test terminals like KC13 said on the defrost board. Jump them for a defrost.

OK, I usually jump with a piece of insulted wire stripped on ends. I will look for the test terminals and report back, may take couple of days