heat and a/c still not working, heating elements work

[spdrcr]

http://mobilehomerepair.com/phpbb/viewtopic.php?t=1700

^^ link to previous thread ^^

ok i got my parts in today.... i replaced the sequencer, t-stat reversing relay, blower relay, both switches (cool/heat and on/auto) thermostat. i also checked the transformer and got the 24v (or something real close) coming out so it should be good right?i checked the operation of the unit after each part change... the intermittent variable was eliminated by the auto/on switch, now i have the same symtoms that i can duplicate, so maybe we can get somewhere now...

if the t-stat is at the lowest setting and the unit set to auto & cool, the outside unit chatters and the blower relay chatters.

if the t-stat is at the lowest setting and the unit is set to off (or standby i guess you could call it) and the fan switch is set to ON, the blower relay chatters....

if the t-stat is at the highest setting and the unit is in standby and fan is set to on, the t-stat rev. relay AND the blower relay chatter

if the t-stat is set to the highest setting and auto/heat there is about a 30 sec pause then heating elements come on (can see and feel of course) then after another 12-13 secs there is a click and heat elements turn off, a few seconds later another click elements come on again... this goes on until finally enough heat builds up (because fan isnt running) that it seems the high temp switch is tripped.... while the high temp switch is tripped i cannot duplicate ANY of the chattering symptoms with t-stat or any switch in ANY position....

i also noticed once when the heating elements were on one time, and i turned the heat/cool switch to standby the heating elements stayed on for a few more secs (i figured this to be the sequencer controlling that...)

please help, i know i have been a Pain in the Neck but i gotta get this thing fixed... i have the ability to go further i just need knowledge... i have experience in testing circuits and whatnot, just not real familiar with residential wiring....

also please correct me in any of my comments and things that i "figured" i take critisizm well....

thanks in advance!!

Jason

[Robert]

Hi Jason,

Still in Holiday mode, will start reading everything and replying beginning tomorrow.


I'll see what I can do.




Thanks,
Robert

[spdrcr]

ok thanks.. just made a new thread because i thought maybe the original might be getting too long and starting fresh sometimes helps... hope you had a good holiday... thanks for your help

god bless!

[spdrcr]

well i just had a repairman leave, he checked over my wiring from where i replaced the parts, everything is good....

he isolated the t-stat and outside units (by unhooking 4 small wires in top of the 2 wire relay box) and the relays still chatter

when he manually applies power to the blower relay, it still chatters

when he takes the wires off the relay and manually applies power, it energizes normally

when he unplugs the blower plug, the unit loses ALL power, no 24V at all....

he asked me to get a diagram of the furnace with the a/c package... the one that was on the furnace cover is destroyed....

he says something is either wired incorrectly on the furnace part (the part without the diagram) or there is a break in the circuit somehwere...

this is getting expensive... i hope this info will help you help me...

thanks again in advance...

[Robert]

How many wires are connected to your t-stat ?

Does your t-stat have a Heat/Cool switch and a Fan/Off/ON switch ?


What 4 wires did he unhook to isolate the t-stat and condenser unit ?


You keep saying they chatter, even the outside unit. What do you mean by chatter ?



With a 2 wire relay box, you should only have 2 wires connected at t-stat.




Thanks,
Robert

[spdrcr]

2 wires at t-stat....

on top of the 2 wire relay box there is 4 wires... 2 go outside to the outside unit..(so i was told) and 2 go to the t-stat....

when it is in a/c mode and t-stat calls for cool (all the way down), then the outside unit will chatter also... but it wont do that in heat...

t-stat has no heat/cool switch or fan/auto switch...

the heat cool and fan auto switch are in the air handler closet... on the 2-wire relay box (nordyne p/n 901698)

when i say chatter, the t-stat reversing relay and the blower relay chatter, like they energize off and on very fast, like many times per second... there is the same noise from the outside unit in cool mode also...

the hvac guy figured there was a short somehwere.. so he was trying to find it by disconnecting the wires to the t-stat and the wires to the outside unit.. when he does this they still chatter (relays inside only of course)

but then he unhooked the blower and he lost all 24V power... that just completely baffled him (and me as well although i didnt realize how weird it was until i thought it through)

[Robert]

Ok, had to get a visual and I am there. ALL chatters are components with 24 volt contacts.

For it to do as you state, I agree on a short somewhere.


Let me think on it some and see what I can come up with to isolate it better.



Thanks,
Robert

[spdrcr]

ok, thanks... im supposed to call this guy back if i get a wiring diagram for the furnace part... he wants to rule out the possibility of it being wired wrong, but i know it is the same as it was before... but do you know where i can get a diagram?

he says it should be for the furnace WITH the a/c package...

he said usually when the a/c is installed they stick a wiring diagram decal on the furnace, and this one is not readable...

but id rather fix it myself with your help so if you have another idea.. by all means shoot it to me...

[spdrcr]

i just checked for 24v power myself, i only lose power on the transformer in the 2-wire relay box, the one on the furnace still has power when i unplug the blower plug....

[Robert]

What was your furnace model number again ?


You have TWO transformers ?


One in a/c control box and one in furnace control box ?



If so, what is the VA rating for one in the a/c control box ?


You can order wiring/parts diagrams here:

http://www.mobilehomerepair.com/wireandparts.html


Ask for furnace and 2 wire a/c control box diagrams.




Thanks,
Robert

[spdrcr]

3500 a 812

yes one is at the furnace, one is in the 2 wire box

furnace 10VA
2 wire 40 VA

[Robert]

Go to link I gave to order awiring diagram for your furnace only.


Then when it arrives by email, go here:

http://www.mobilehomerepair.com/ColemanAC.html



Scroll down left side to 2 wire a/c control box # 3500-5821/A.


Click on more info and scroll down to wiring diagram.



You MUST have between 24 and 28VAC at those transformers.


Keep t-stat set at temp you want home to be.


Your wall t-stat DOES NOT control a/c mode, that is controlled by t-stat reversing relay.


Your sequencer controls elements and blower motor for heat mode.


Blower relay controls motor for a/c mode and when furnace fan

switch is set to ON.



T-Stat stays at desired room temp, furnace switches stay at Auto and Cool or Heat, depending on season.



If all wiring is ok, look closely for loose wiring, shorts or low voltage from transformer.


If needed, you can get a 4 wire t-stat and wire up and reduce relays.


Because it involves condenser unit in a/c mode, sounds like it is definately a 24 volt problem.


It is easy to cross a wire and cause a hiccup in system.



Thanks,
Robert

[spdrcr]

my 2 wire relay box is different.... it is a 901968 nordyne p/n, i have a wiring diagram for that inside the cover of the 2 wire relay box....

both transformers have 28 VAC coming out....

transformers never disconnected... all wiring in 2 wire relay box is correct according to diagram....

i was really careful when replacing wires, i drew my own diagrams, i took digital pics and everything before i touched anything... i checked for loose wiring and couldnt find any.. i guess my next step is to individually ohm each wire...

[Robert]

http://www.mobilehomerepair.com/media/i ... 901698.pdf


Be sure you don't have any wires crossed over. Disconnect and rewire all power (24vac low voltage) side and then all neutral side.



Thanks,
Robert

[spdrcr]

still no response on whether the link you gave me has the wiring diagram....

my HVAC guy is also not able to get a wiring diagram....

i have traced each and every wire and they are all correct...

one more thing to keep in mind... the chattering relays started BEFORE any wires were touched or ANY parts were changed, 100% sure of that....

is it possible that the transformer is bad in such a way that when a load is put on it, the voltage drops out, causing the relay to de-energize, then the voltage comes back causing it to re-energize... maybe this would cause my relay chattering problem?? i really dont know but i do have a vivid imagination...

i have tried to measure the voltage at the transformer while the relays were chattering.... inconclusive... the voltage jumps all around and appears to read around 300-1200 VAC.. lol that cant be... (digital meter)

if you can think of anything else let me know, i will continue to wait for a diagram to make sure everything is like its supposed to be

thanks,
Jason