Carrier Furnace Error Code 33

[s6skuzy01]

Have a 11 yr old Carrier 80% furnace 58RAV. Back in the fall of 2008 the furnace would go on and shutoff. Called an HVAC mechanic and they replaced a the limit switch and it worked fine for about a month. Then, every 30-45 days since the repair, we get an error code 33. I replaced the filter (it wasnt more than 30-45 days old). Problem went away for 3-045 days then happened again. Called HVAC mechanic out and he just adjusted the fan speed up a notch and replaced the filter. 45 days later it happened again. As soon as I replace the filter the error code stops. The filters are dirty, but we have gone longer than 30-45 days before the initial repair without getting the error. We will call teh HVAC mechanic again and see what the scoop is, but the last time out they didnt seem to know what was causing the error. Any ideas?



Thanks

[referrob]

sounds like you already solved your problem with a filter change. depending on how many people and pets are in the house and if fan is on 24/7 or only when heating or cooling the filter may need to be change monthly and at least every 3 months. you may also need to have your return and supply ducts checked for crushed or animal damaged areas if your house was run with flex duct.

[s6skuzy01]

Thanks for your reply...

Before the limit switch was replaced, we could get more than 45 days out of a filter (if I forgot to change). We have no pets and we were changing the filters every couple months before this started. Now we can only get 30-45 days before this happens..

[screws]

Sounds like the filter is the problem but do you have any registers closed it just a thought. Make sure when you call out the service tech they check the td across the unit.

[beenthere]

Could accidentally have used the wrong limit switch.
May also have a dirty A/C coil.

Did they check temp rise when they were there.

[superheatrman]

Sounds like your 11 year old furnace is low on air flow and the evaporator is clogged with dirt. A temperature rise measurement will show this.

[21degrees]

Because if he did not do a couple simple test, than maybe you have wrong company. To many variables to speculate on.

[Twilly]

Twilli wonders could it be the thermostat?

[cstock]

Are you using a different brand of filter? Did your serviceman use a different brand of filter? There are some very restrictive filters out there.

[s6skuzy01]

The tech left and found temp range after A coil:

Without filter - 130
With old filter - 155 and temp sensor tripped
With new filter - 144

He adjusted the gas and the temp range was withing specs. When they replaced the limit switch, they put one in that allowed for a larger temp range, so they didnt think that was the issue. Also said to use a different filter. Our current filter is a MERV 6.

He wanted to put another cold air return by the furnance, but I declined at this point. We'll see if this fixes it...

[glfdad26]

check static pressures

[superheatrman]

144F still gives you 75F temp. rise appears to still be running to hot. The temp rise is on the manufactures label . 45F-70F is standard on most 80% furnaces. Add that ductwork.

[gasguy]

144F still gives you 75F temp. rise appears to still be running to hot. The temp rise is on the manufactures label . 45F-70F is standard on most 80% furnaces. Add that ductwork.

Just wondering how you got a 75* temp rise? I didn't see a return temp posted?

I would get the tech back and have the heat exchanger checked. I just had the exact same thing just this morning with a 12yr old Bryant that is identical to your Carrier. Showing code 33; limit fault. The limit switch was stuck open. Found a dirty filter, and almost half the supply registers closed. Pulled the blower and found 3 of 4 HX cells cracked. Two on both sides! These furnaces will not take alot of overheating.