'90 cooling fan adjustment?
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 42
From: Baltimore, MD USA
So i am new to the vette world with my 94. My car runs really hot in traffice and town as well but fine on the highway. Noticed in town with ac on it stays cool fine but without it on it will not stay cool. From what i have gathered here it seems like my ac cooling fan is doing all the work and my primary isn't coming on at all. I have been under the hood waiting for it to come on and it never does even when car is in the red. I found the information here helpful and i am going to try to jumper the connections to see if the fans come on. If they don't please clarify for me jumping the 2 grounds on the relay will make the fans both fans come on when the ac calls but that wont help me a bunch unless the ac is on?
The 94 uses an OBDII diagnostic connector so jumping pins on the connector won't work. The GM service tech would use a Tech 1 to verify the fans work.
There are 3 relays on the drive side of the radiator shroud. You can identify which relay is which by looking at the color of the wires at each relay socket.
Relay #1 has Pink, Dark Green, Red and a Light Blue wire.
Relay #2 has Pink, Dark Blue, Red and a White wire.
Relay #3 has Pink, Dark Blue, Black, White and another Black Wire.
Both fans are either on at low speed and at Hi speed. They never run individually.
For low speed the Dark Green wire is grounded by the PCM.
Relay #1 closes. Both fans are in series and run on 6 volts.
For hi speed the Dark Green wire and the Dark Blue wire are grounded by the PCM.
All three relays close and each fan runs off of 12 volts. (Hi speed).
To test the fans, turn the ignition On.
If you want to manually turn the fans on low speed ground the Dark Green wire at the relay socket.
If you want to manually turn the fans on hi speed ground the Dark Green wire and the Dark Blue wire.
Pro
Joined: Jun 2007
Posts: 626
Likes: 2
From: Coquitlam British Columbia
On my 1990 Vert; I put 2 rocker switches in the blank spot (FX3 control delete) between the seat adjustment control and ran wiring to each fan relay then to ground. Now I can run one or both fans when needed at a flip of a switch. No need for fans at cruising but if you see traffic coming turn on #1 and if stuck in traffic hit the second one. Had this set up for several years and like the idea of controlling the fans ...note...ECM will still work to turn on if I forget .
Bill
Bill
