C-4 Secondary Coolant Fan Operation
Thread Starter
Heel & Toe
Joined: Sep 2014
Posts: 22
Likes: 1
From: Boyne City MI
C-4 Secondary Coolant Fan Operation
I need a little help understanding the operation and purpose of the secondary fan in my '92. I thought that this fan should operate if an ECM code is set or certain coolant/oil temps are exceeded and ALSO when the A/C is turned on. However, my secondary does not turn on with the A/C. I'm not sure if this is normal or if I have a problem. Any thoughts would be appreciated.
Pro
Joined: Oct 2008
Posts: 706
Likes: 265
From: Jyväskylä, FINLAND
In 1991, if you connect the A and B in the ALDL connector and turn the ignition to on (do not start), ECM will turn both fans on. The easiest way to check that both fans do work. (I don't know, if this still works with 92 and up)
Thread Starter
Heel & Toe
Joined: Sep 2014
Posts: 22
Likes: 1
From: Boyne City MI
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
If jumpering pins A and B start only one fan, try swapping the two cooling fan relays. They are both the same so if the secondary fan works after swapping the relay and primary fan doesn't, get a new relay.
Also make sure the A/C is working properly. Issues like low pressure may not turn on the secondary fan.
Also make sure the A/C is working properly. Issues like low pressure may not turn on the secondary fan.
Thread Starter
Heel & Toe
Joined: Sep 2014
Posts: 22
Likes: 1
From: Boyne City MI
If jumpering pins A and B start only one fan, try swapping the two cooling fan relays. They are both the same so if the secondary fan works after swapping the relay and primary fan doesn't, get a new relay.
Also make sure the A/C is working properly. Issues like low pressure may not turn on the secondary fan.
Also make sure the A/C is working properly. Issues like low pressure may not turn on the secondary fan.
