Lights and heater fan blink on and off - 2004 GMC Sierra

For bower fan check:
- Speed controller assembly of blower fan.
- Wiring harness and fuse
- Blower fan.
To solve the air bag light problem retrieve the SRS error codes with the help of diagnostic computer and follow the description.
You can also check the error codes manually as described below.


Procedure:
Read the blinking patterns of the DTCs. As examples, the blinking patterns for the normal system code and DTCs 11 and 31 are shown in the following diagram. The first blinking pattern indicates the first digit DTC. The second blinking pattern occurs after a 1.5-second pause. If there are two or more DTCs, there is a 2.5- second pause between each DTC. After all DTCs are shown, there is a 4.0-second pause, and they are all repeated.
HINT:
• If 2 or more malfunctions are found, the indication begins with the lowest numbered DTC.

Check the connections on both ends of both battery cables (particularly the main negative cable to engine and body grounds) - clean and reinstall. Could also be connection going bad on the fusible link in the battery + cable, or a faulty fusible link.

The cooling and heating systems in this car have self diagnosis and blink the two lights in the lower right corner if there is a fault. Are these blinking? If so what pattern. I am going to assume you have checked the fuse. If that is good you may need to take the motor out and test that. This take a Torx driver. 6 of these takes the glove box insert out and then 3 more take the motor out it is a tight squeeze but after a while you'll get it (no real tips on how to it takes some time) then you can test this with a battery charger or other 12 source. If the fan works here then there is a fault in the wiring or in the switch-box itself.

Make sure your fan is wired correctly, if the fan is wired correclty which it may but could be crossed and spinning backward and sending power through ground wire causing a power up of the inside light and blower, if the wiring is good then replace the cooling fan relay, that must be shorting and back feeding power to heater control.

Then chances are these is an obstruction in the blower motor or the motor is worn out. The blinking lights indicate a fault in the system. Let me know which car you have and I can walk you though the replacement/rehab process.
I have had good luck after removing the blower motor hooking it up to a battery charger and putting it on 20 amps and lubing the daylights out of it. Has saved me hundreds!

Hi,

The overheating and lack of cabin heat both point to a failed engine thermostat which would be stuck closed. At the warm up stage, the coolant stays in the engine block to bring the engine to efficient operating temperature, then it opens and circulates the coolant through the radiator and heat core. If the thermostat is stuck closed, the engine will overheat, and coolant will never reach the heater core, and you will not get cabin heat.

Blinking oil light at idle which goes away during driving could be a low oil level, but may also be a drop in oil pressue. You could have a clogged oil fliter (at best) pickup tube, or a failing oil pump.

It sounds as if you may have an air pocket in the system, alot of your saturn and gm vehicles have air bleed on or near the thermostat housing. As you are filling the system you will need to have this bleeder open until a steady stream of coolant comes out.

Since warm air eventually comes out when the vehicle is in motion, you may have an air mix door that is stuck in fresh or is somehow blocking warm air from the heater core.

To see if the air mix control motor is bad, you need to retrieve your Diagnostic trouble codes (DTC's) from the heater control panel. To run the diagnostic function, do the following:
1. Turn the ignition switch ON (II).
2. Turn the fan switch OFF.
3. Press the recirc control button to select Recirc (recirc light on.)
4. Press and hold the recirc button to select Fresh (recirc light off) and continue to hold the button down until the recirc light comes on for two seconds and then goes off.
5. If the system is okay, the recirc light stays off.
6. If there is a problem, the recirc light blinks the DTC to indicate the trouble. One blink=a problem in the air mix control motor circuit. Two blinks=problem in the mode control motor circuit
Three blinks=problem in evaporator temp sensor circuit.
7. Turn the ignition switch off to cancel the self diagnosis function. Run the diagnostic again after repairs are complete.

Note: the air mix control motor has a rod which connects to a plastic link. The link controls the mix doors and also connects to the heater control water valve via a cable. The air mix motor may check okay, but if the link is broken then you will still have problems. the motor is on the bottom of the heater unit in the front passenger's foot well.

The A/C pressure switch is located in the high pressure line (the skinny one) on the passenger side of the engine compartment just under the fuse/relay box. The switch has three functions: <28 psi, the switch opens to protect the compressor from lack of lubrication. >220 psi, the switch shifts the radiator and compressor fan to high speed. >455 psi, the switch opens to protect the compressor seals. Check to see if you have any powertrain DTC's first. A faulty engine coolant temp sensor can cause problems with the compressor clutch relay. If the radiator and compressor fan come on with the A/C on but the compressor clutch does not operate, check the compressor clutch relay. You can also obtain Heater control panel diagnostic trouble codes (DTC's) by turning the ignition switch on. Then turn fan switch off. Press recirc button to select recirc air. Press and hold recirc to turn off recirc air but this time continue to hold the button down until recirc light comes on for two seconds and then goes off. If there is any trouble, the recirc light will then blink a code (if no trouble, the light will remain off) 1 blink = problem in air mix control motor circuit. 2 blinks = a problem in mode control motor circuit. 3 blinks = a problem in evaporator temperature sensor circuit. (this one could be a factor in your case) Turn the ignition switch off to end the test.

Hello,
sounds like the (VSS)vehicle speed sensor is bad causing the speedo not to work and the transmission is not shifting properly because the computer can not tell how fast the car is going,have your local mechanic fix it asap so toy do not do any engine or transmission problems.as far as the heater stopping,I dont thing they are related.I will get back to you on the blower have a good day DB