Chevy Nova Forum banner

1 - 6 of 6 Posts

·
Registered
Joined
·
2 Posts
Discussion Starter #1
Alright so I just bought my grand fathers 74 Nova from him and noticed it had a factory AC and heater on it. Last Winter I would use the defog/heater but noticed it only worked on Low/medium fan speed. This year I'm looking to use her more and noticed that I have no fan operation at all. I was just wondering where should I start to trouble shoot both issues? The fact that it doesnt turn on anymore at all and why only some speeds worked and some didnt? Any help would be appreciated.
 

·
Registered
Joined
·
4,658 Posts
OK
1st question : when the fan motor ran , did it make noise, ran smooth, blow out the vents ?

2nd : did it just STOP at once ?



Check the power: at the fuse box, check the fuse. (fuse labeled as heater).
locate the 'Blower Motor' ..... can you see or get to the motor? check that the power wire is connected ... can you get to that pwr wire ... check that wire for power (with a test light -- that will just show there is power (no different speeds).

Mostly : it will have pwr - or - have NO pwr ... after u check the fuse.
motor could be locked-up (need another motor) or may spin ok (spins smooth or makes noise ?). just take steps and check things out to determine which part may work - or - not work.
Then, move to why heater motor runs at different speeds ........ that maybe be connected by a bad "heater fan switch -- or another issue".

keep us posted .
 

·
Registered
Joined
·
56 Posts
Factory AC car should have 5 components for the blower

Blower relay
Blower resistor
Blower motor
Blower switch
Fuse

You really need an electrical meter or test light to diagnose any of these items
 

·
Registered
Joined
·
2,300 Posts
Yuck. I had a gut full of blower motor issues this year.

All I can say at this point is you better hope your problem is under the hood. Getting to the actual fan motor will be the least fun you've had in a decade.

There are plenty of places where you could have an issue, so sit back and get ready for the possibility of a long ride to get this fixed. Follow the tips above, and you can also search the Electrical forum for my troubleshooting thread there. I had a lot of help in tracing through the fan system and I documented a lot of my testing, so maybe my pains will help you track down your issue.
 

·
Registered
Joined
·
514 Posts
The fan switch has 4 positions: off, low, medium and high. Low and medium speed run from a fuse in the fuse panel through set of resistors, but high speed runs with a large relay and located on top of the AC evaporator box (under the hood) and a dedicated wire and fuse located in the engine bay. If low and medium speed were working but high was not there was probably an issue with the high speed fan relay or the underhood wiring or fuse.

If none of the speeds are working you may have the original problem still with the high speed circuit and a new problem with the low/medium speed circuits. Or you might have a problem with the ground or power connections at the blower. Or you might have a problem with the blower. Or you might have a problem with the fan switch.

The first thing I would check is the fuse in the interior fuse panel. It should be marked "AC". If that fuse looks good, I would get a voltmeter out and start checking to see if you are getting voltage to the blower when the ignition is on and the fan switch is in low or medium position. If not, then you can work your way back to see if there is an issue with one of the connections or the blower relays. If you are getting voltage, then you can check the power and ground connections at the blower which is a little tough to access without lowering the inner fender on the passenger side. If those check out, you can check the resistance of the blower to see if it has shorter or opened.

Once you have the low/medium troubleshooting done, check the high speed relay and the fuse for high speed. An easy way to check the relay operation is to turn the ignition switch on and then listen for the relay "click" when you move the fan switch from medium to high and back. The fuse is in an inline holder under the hood and it should be relatively easy to check.
 

·
Registered
Joined
·
4,658 Posts
The fan switch has 4 positions: off, low, medium and high. Low and medium speed run from a fuse in the fuse panel through set of resistors, but high speed runs with a large relay and located on top of the AC evaporator box (under the hood) and a dedicated wire and fuse located in the engine bay. If low and medium speed were working but high was not there was probably an issue with the high speed fan relay or the underhood wiring or fuse.

If none of the speeds are working you may have the original problem still with the high speed circuit and a new problem with the low/medium speed circuits. Or you might have a problem with the ground or power connections at the blower. Or you might have a problem with the blower. Or you might have a problem with the fan switch.

The first thing I would check is the fuse in the interior fuse panel. It should be marked "AC". If that fuse looks good, I would get a voltmeter out and start checking to see if you are getting voltage to the blower when the ignition is on and the fan switch is in low or medium position. If not, then you can work your way back to see if there is an issue with one of the connections or the blower relays. If you are getting voltage, then you can check the power and ground connections at the blower which is a little tough to access without lowering the inner fender on the passenger side. If those check out, you can check the resistance of the blower to see if it has shorter or opened.

Once you have the low/medium troubleshooting done, check the high speed relay and the fuse for high speed. An easy way to check the relay operation is to turn the ignition switch on and then listen for the relay "click" when you move the fan switch from medium to high and back. The fuse is in an inline holder under the hood and it should be relatively easy to check.
Good job , Clint

I just gave him the "short version" ..... and, you gave him the more "complete vacation package" .
It works for me ...... thanks, Clint
 
1 - 6 of 6 Posts
Top