Blower runs but elec. heat strips dont work - Intertherm P3RC-030K Air Conditioner

Some blowers shut off depending on the system. Do you have electric hest strips inside? If not the blower will shut off. The outdoor fan should not be running if in defrost mode. If you have heat strips then you likely have low voltage wiring crossed

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Sounds like the blower motor is wired to the load side of the A/C contactor relay/. In this condition the blower will only run when the compressor is running which is ok for a heat pump but if you are running electric heat only the blower motor needs one wire to the line side and one to the fan relay. That way the blower will run with heat or a/c. When the blower wont run the heat strips thermal protection will cycle them on and off

Will be to clean each contact-switch and scrape the contacts and use wd40 and spray of air and remove all rust, its possible that exist another options of failure.

Duct is slightly undersized but if it's ran for 130 years like that then let it go. 100 degrees supply air temp??? That's pretty warm for a fan in high speed. Verify amps on your fan motor. Verify amps on the element. Monitor amps on element to see if it starts to rise. Also be sure you are putting the right limit switch in. (As far as temp) Good luck!!

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Probably a bad limit switch on the strips or the heat sequencer/relay is falling out after continued amp draw. I would lean toward the heat relay/sequencer. Havent heard of any problems with coleman limit switches. These units were prone to get water inthe electrical compartments due to the evap coil being right above it. Check to see where the power break is starting at the strips and working backwards throught the circuit. That will tell you for sure. Make sure you have 24v going to the heat sequencer too.

Is there a setting on the thermostat for Auto or Fan? If so, make sure it is in the Auto setting. You will have a contactor that turns on the elements and a relay for the fan. Follow the wiring diagram to see which relay energizes the fan then unplug it to see if the fan stops.

On a Trane furnace the fan realy must energize before the electric strips will come on. On the thermastat. See if there is setting for electric heat. This will bring the fan on and the strips should come on. First just turn on your heat and and turn fan to on postion if it works you need to set tstat to electric heat mode. Most of the time there is sswitch in the back of the stat that says gas elec. Turn to electric. Rus

Do this.

press "Home"
press "Help"
press both "My Cycles" and "Back" at the same time and hold them until service mode pops up.
It will tell you what's wrong.

There should be electric heat strips in the airhandler.

They automatically come on when the unit goes into defrost, the thermostat is turned up more than 7 degrees over the indoor temp or if the outdoor temp is just so cold the HP cannot keep up.

Tat is your auxillary or emergency heat.

What does the new t-stats installers booklet say that the 0170 function and #2 #7 options are for?

If it is for gas vs elec heat then set it on the elec option.

The difference is that in gas heat systems the blower comes on a few min AFTER the furnace fires up to allow the heat exchanger to get hot.
In an electric furnace the blower has to come on emediatly because the heat strips get hot emediatly and if the blower is delayed the system will shut of in high temp overload.

SINCE YOU SAID AC I ASSUME YOU HAVE ELECTRIC HEAT. IF BLOWER IS ON BUT NO HEAT THEN YOUR HEAT STRIPS ARE PROBABNLY NOT BEING TOLD TO COME ON OR THE BREAKER TO THEM IS OFF. SOME TIMES THE BLOWER IS ON A BREAKER AND THE STRIPS ARE ON A SEPERATE. CHECK ALL BREAKERS. THEN IF STILL NO HEAT YOULL HAVE TO CHECK THE POWER TO THE HEAT STRIP RELAYS . SEE IF THEY ARE BEING SENT A 24 VOLT SIGNAL TO RUN AND THEN CHECK TO SEE IF THEY HAVE POWER INTO AND OUT OF THE RELAYS. IF YOU DO THEN AN OVERLOAD OR A FUSEABLE LINK OR THE STRIPS THEMSELVES ARE BAD. EACH 5 KW OF HEAT SHOULD PULL 20 AMPS . IE 15 KW PULLS 60 AMPS 10KW PULLS 40 AMPS ETC.