Mdl #MHU80 combustion blower turns on no ignition LED flashing 3 times and blower shuts off.

They are listed inside the front panel of the main unit.
LED CODE
EACH OF THE FOLLOWING STATUS CODES IS A TWO DIGIT NUMBER WITH THE FIRST
DIGIT DETERMINED BY THE NUMBER OF SHORT FLASHES AND THE SECOND DIGIT BY
THE NUMBER OF LONG FLASHES.
STATUS

11 NO PREVIOUS CODE - Stored status code is erased automatically after 72
hours. On RED LED boards stored status codes can also be erased when power
(115 VAC or 24 VAC) to control is interrupted.
12 BLOWER ON AFTER POWER UP (115 VAC or 24 VAC) -Blower runs for 90
seconds, if unit is powered up during a call for heat (R-W closed) or R-W opens
during blower on-delay.
13 LIMIT CIRCUIT LOCKOUT - Lockout occurs if the limit or flame rollout switch is
open longer than 3 minutes.
- Control will auto reset after three hours. - Refer to #33.
14 IGNITION LOCKOUT - Control will auto-reset after three hours. Refer to #34.
21 GAS HEATING LOCKOUT - Control will NOT auto reset.
Check for: - Mis-wired gas valve -Defective control (valve relay)
22 ABNORMAL FLAME-PROVING SIGNAL - Flame is proved while gas valve is
de-energized. Inducer will run until fault is cleared. Check for:
- Leaky gas valve - Stuck-open gas valve
23 PRESSURE SWITCH DID NOT OPEN Check for:
- Obstructed pressure tubing. - Pressure switch stuck closed.
24 SECONDARY VOLTAGE FUSE IS OPEN Check for:
- Short circuit in secondary voltage (24VAC) wiring.
31 PRESSURE SWITCH DID NOT CLOSE OR REOPENED - If open longer than
five minutes, inducer shuts off for 15 minutes before retry. Check for:
- Excessive wind - Proper vent sizing - Defective inducer motor
- Low inducer voltage (115VAC) - Defective pressure switch
- Inadequate combustion air supply - Restricted vent
- Disconnected or obstructed pressure tubing
- Low inlet gas pressure (if LGPS used)
If it opens during blower on-delay period, blower will come on for the selected
blower off-delay.
33 LIMIT CIRCUIT FAULT - Indicates a limit, or flame rollout is open. Blower will
run for 4 minutes or until open switch remakes whichever is longer. If open
longer than 3 minutes, code changes to lockout #13. If open less than 3 minutes
status code #33 continues to flash until blower shuts off. Flame rollout switch
requires manual reset. Check for: - Restricted vent
- Proper vent sizing - Loose blower wheel - Excessive wind
- Dirty filter or restricted duct system.
- Defective blower motor or capacitor. - Defective switch or connections.
- Inadequate combustion air supply (Flame Roll-out Switch open).
34 IGNITION PROVING FAILURE - Control will try three more times before lockout
#14 occurs. If flame signal lost during blower on-delay period, blower will come
on for the selected blower off-delay. Check for: - Control ground continuity
- Flame sensor must not be grounded
- Oxide buildup on flame sensor (clean with fine steel wool).
- Proper flame sense microamps (.5 microamps D.C. min., 4.0 - 6.0 nominal).
- Gas valve defective or gas valve turned off - Manual valve shut-off
- Defective Hot Surface Ignitor
- Low inlet gas pressure
- Inadequate flame carryover or rough ignition
- Green/Yellow wire MUST be connected to furnace sheet metal
45 CONTROL CIRCUITRY LOCKOUT Auto-reset after one hour lockout due to;
- Gas valve relay stuck open - Flame sense circuit failure
- Software check error
Reset power to clear lockout. Replace control if status code repeats.
If status code recall is needed, briefly remove then reconnect one main limit wire to display
stored status code. On RED LED boards do not remove power or blower door before initiatingstatus code recall. After one status code recall is completed component test will occur.

here is a link copy and paste

https://www.fixya.com/support/t6287232-carrier_8000ts


.

Steady light on - normal operation.
One flash - ignition failure.
Two flashes - combustion air switch stuck closed.
Three flashes - combustion air switch failed to close.
Four flashes - limit switch open.
Five flashes - gas valve energized with no call for heat.
Rapid flashing - reversed polarity.

Note: Color of light is green.

You may have high carbon buildup in your piston/cylinder. The engine may fire via a DIESEL ignition. That is, as the fuel compresses in the compression stroke, it ignites just from the residual heat in the hot carbon in the combustion chamber (like an old 1970s car). Try a higher octane fuel (up to 92 or 93). Higher octane resists combustion until the soarkplug fires.

Your combustion motor is the very first thing to cycle when theres a call for heat. Look at your access panel. There should be a LED status indicator chart. It will tell you what the flashing LED means and what your most likely problem is.

When there is a Call for heat, the control delays ignition until combustion air

Blower operation has been proved and pre-purge period

Has elapsed. It then opens the gas valve and generates a

Spark to ignite the burners. Trial for ignition lasts for 7 seconds.

At the same time, the control begins monitoring the

Flame sensor. If the flame current is too weak (less than 1

Micro amp) or if the burners do not ignite (within the 7 second

Ignition trial), the control will shut off spark and the combustion

Air blower and de-energize the gas valve. Flame

Current should be between 1 and 5 micro amps to keep the

Gas valve open.

The control will attempt to ignite the burners up to two more

Times. Each time the control restarts the ignition sequence,

It begins with a 45 second pre-purge. If flame is not sensed

After the third trial, the control locks out. Lockout means that

The control shuts off the gas valve, spark and combustion air

Blower for 60 minutes. At the end of 60 minutes the control

Completely resets and will attempt ignition up to three times.

The control can be manually reset before the end of 60 minutes

By momentarily turning off power to the unit.

here is a link to an operations manual

http://0190acd.netsolhost.com/manuals/80MGF_Series.pdf

1
1 FLASH
Furnace fails to operate.
• Integrated control module
diagnostic LED is
flashing ONE (1) flash.
• Furnace lockout due
to an excessive
number of ignition
“retries” (3 total)1.
• Failure to establish flame.
Cause may be no gas to
burners, front cover
pressure switch stuck open,
bad igniter or igniter
alignment, improper orifices,
or coated/oxidized or
improperly connected flame
sensor.
• Loss of flame after establishment.
Cause may be
interrupted gas supply, lazy
burner flames (improper gas
pressure or restriction in flue
and/or combustion air
piping), front cover pressure
switch opening, or improper
induced draft blower
performance.
• Locate and correct gas
interruption.
• Check front cover
pressure switch
operation (hose, wiring,
contact operation).
Correct if necessary.
• Replace or realign
igniter.
• Check flame sense
signal. Sand sensor if
coated and/or oxidized.
• Check flue piping for
blockage, proper
length, elbows, and
termination.
• Verify proper induced
draft blower performance.

I Also have the same and other problems with my furnace model # GDS80703AXBB. First the LED kept blinking 4 times and I too jumped the primary limit, that didn't kelp. After several attemps I moved the wires going to the circut board and everything starting working again. After a week It stopped working again, so I pulled the plug out of the circut board checked all wires for for a bad connection plugged it back in. Now the LED blinks 6 times again I move the wires. Then the LED blinks 3 times. Then the transformer burns out. I have burned out 2 transformers and I have ordered a new circut board.

You should be seeing 120 volts to the igniter. Anything less requires either a replacement of the transformer, start relay or control module.