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Hello all. I have a ‘71 Cutlass and have no idea how to go about troubleshooting the HVAC controls/system. The a/c compressor and lines have been removed years ago but really all I’m focusing on is the blower. I’ve been wanting to drive the car to work once in awhile but without defrost, it’s almost impossible with the morning dew on the windshield. The blower speed controls do nothing. Any pointers on where to look? All fuses are good. Thanks for any and all help.
You might check the blower motor resistor or the blower motor relay. They are both shown in the Chassis Service Manual (CSM). If you don't have a CSM, you should get one.
Just to be clear, do you have the main control set to VENT or DEF while you are changing the blower speed? If it is in the OFF position, the fan will not run.
It sounds as if there is either no power getting to the blower motor or the blower motor itself is faulty. Start by checking the things Will22 mentioned above as those are very simple inspections that don't require diagnostic tools (see image below).
Find your factory chassis service manual as there is a step-by-step troubleshooting diagram for blower problems. The only diagnostic tool you will need is a voltmeter or test light. If your blower motor does not work at all, it is either dead and needs to be replaced, or it is not getting power. The manual will tell you how and where to check for power.
Here's one now, but you'll find more. Just search under "1971 Oldsmobile manual" or something similar. Get the 1971 Fisher Body Manual as well as some topics, such as doors and windows, are covered in there and not in the chassis manual.
Yesterday evening I checked the voltage at the 4 terminals shown above. Only two of them read power. They were fan switch position 2 and position 3. Low and High did not read at all. I cleaned the terminals and plugged it back in. The blower still wouldn't work on any speed. I'm guessing the motor is locked up. The connector wasn't melted but at one terminal I could tell it'd been hot before.
Below is the blower motor troubleshooting diagram for 1971 A-body Oldsmobiles with air conditioning when the blower motor is inoperative at any speed setting. You want to follow this carefully until you identify the problem. The rest of the manual will have the diagrams you need to find the various components to attach the test light or voltmeter to. I'm going to guess that you need a new blower motor, as you suggest.
Thanks! I plan on buying the service manual soon. I only drive the car occasionally. The rest of the time it's covered up in the garage. Now my kids are getting to the age where they want to take it everywhere.
October 3rd, 2018, 07:45 AM
