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Discussion Starter #1
Hey yall,

(I let the car sit for longer than I care to admit.... So naturally I'm working my way through some issues)

Have an issue, I'm still reading up on stuff here but I figured i'd ask about something I'm still unclear on.

I've read and witnessed that the primary fan comes on when there is a high temp or when I turn on the A/C. My question is when I have the A/C switch on>> what actually tells the fan to turn on? The switch? the clutch kicking in?

My issue(s):

I have/had two codes: P1641 and P1642 (relays)> Now before I get told to replace the relays, when i unplug the sensor on the water pump both fans do indeed turn on. So it cant be the relays right?? (I have replaced the relays and fuses anyway HOWEVER both fans turned on when I pulled the connector before i replaced the relays)

Since both fans turned on can I assume there isn't a connection issue, relay issue, melted wires on the fuse/relay block, etc (as other posts I have searched have suggested)? When I let the car heat up the primary fan did ultimately kick on. So I really don't understand the CEL codes I got.

The only remaining outstanding issue is the primary fan does not turn on when I have the HVAC switch in the A/C position. The car does not blow cold. I'm assuming the compressor is bad (I will jumper the switch in the A.M.) Does the compressor have to "work" to kick on the primary fan? Does it need to see some type of pressure? Does a bad/failed compressor cause the same CEL's? There is no clicking in the clutch or on/off cycles like when I was blowing hot air previously.

I think its obvious I have some type of A/C issue. Going to take it to a shop. Just frustrated at the codes I'm getting saying bad relays when I can pull the plug on the water pump and kick the fans on. If i had bad relays, I would assume they would not kick on.

(I'm going to change the motors on the fans themselves anyway because they are pretty loud and squealing. I dont think loud or stressed motors that actually work would cause the CEL codes right?)

Any help would be appreciated.

Rob.
 

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Relay codes

The relay codes only show if there is a problem between the PCM and the relay. The PCM checks if the relay is plugged in and the coil is OK. Removing the relays, pulling the 10 A fuse, flacky relay, bad socket or a bad wire will give this code. When you pull the sensor both fans run so the fans and their fuses are working. I get the same type of fan code on my 94 because I pull the relays when I program the PCM. I clear them and that is that.

Have a look at Manual AC: (Goldwagon's circuit page Link below) "A"

A

The diagram shows there is no direct connection from the fans to the PCM. The PCM does not know if they are spinning or not so they can not throw a code. Bad fan motors may draw high current and run slow. There are other forums that complain of damaged relays and then have to replace the fans after frying a new relay. Since you are replacing the fans try clearing the codes and see if it goes away.

The PCM decides when to turn on the fans and the AC compressor. Low Freon (low pressure) is a common cause.
I would find a good AC shop and get a service. My understanding is adding Freon to a system with air in it is a expensive mistake, it would need to be vacuumed before the new Freon is added.
 

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Discussion Starter #3 (Edited)
baby steps

Just to update::

I cleared the codes and replaced both radiator fan motors. I've driven it for a few hours and no codes have popped up yet.

For an FYI the passenger side Radiator Fan Motor part number P/N is #PM538 and Drivers side is #PM9040. (for my 96BBB, I can't confirm other B-Bodies)



and Remember the nut that attaches the fan blades to the motor is opposite thread. Theres a really good video on youtube on how to change the 96 fan motors. https://www.youtube.com/watch?v=h2JpW_hftaQ They have a few other Impala videos as well.

And about the A/C:
I jumpered the switch on the accumulator and both the A/C Compressor and passenger side fan did indeed turn on. So i'll take it in soon to an A/C shop for a recharge. Hopefully they can find the leak.

Thanks for the help!!


Rob.
 
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