Fan Control Question
Thread Starter
Safety Car
Joined: May 1999
Posts: 3,651
Likes: 5
From: Atlantis
Cruise-In I Veteran
Fan Control Question
I have two cooling fans on my 91 Vette.
There are TWO fan control parameters in the EPROM. Are they the sole controling factors for my fans or is there an additional switch on one of my heads?
Is there a fan control sensor on my 91 Vette?
There are TWO fan control parameters in the EPROM. Are they the sole controling factors for my fans or is there an additional switch on one of my heads?
Is there a fan control sensor on my 91 Vette?
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Re: Fan Control Question (VetNutJim)
All the L-98's use a switch in the left head to ground the circuit for the secondary or aux fan. Stock is 228. ECM driver controls only the main fan. It will ground the main relay when the cooltant temp sensor resistance indicates 226 degrees or when the a/c high pressure switch opens - about 230 psi. If the signal is from the coolant temp sensor, fan runs for a minimum of 30 seconds. If it's from the pressure switch, PCM energizes relay until the psi drops to 170 psi (switch closes).
Thread Starter
Safety Car
Joined: May 1999
Posts: 3,651
Likes: 5
From: Atlantis
Cruise-In I Veteran
Re: Fan Control Question (SunCr)
SunCr,
I don't have a sensor in the left head on my 91. I have one on the RIGHT head. Between 6 and 8.
I suspect it runs the temp gauge.
I have settings in the 8D Calibration file for:
1) Fan 1 On Temp
2) Fan 1 Off Tem
3) Fan 2 On Temp
4) Fan 2 Off Temp
I have two fans. I have two relays.
Any additional ideas?
I don't have a sensor in the left head on my 91. I have one on the RIGHT head. Between 6 and 8.
I suspect it runs the temp gauge.
I have settings in the 8D Calibration file for:
1) Fan 1 On Temp
2) Fan 1 Off Tem
3) Fan 2 On Temp
4) Fan 2 Off Temp
I have two fans. I have two relays.
Any additional ideas?
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Fan Control Question (VetNutJim)
I believe both of your side-by-side fans are fully under ECM control.
On the '85-'89 Vettes the front aux fan was controlled only by the aux fan switch in the block below #1 & # 3 plugs. I don't believe your newer fan setup had that aux temp sensor.
On the '85-'89 Vettes the front aux fan was controlled only by the aux fan switch in the block below #1 & # 3 plugs. I don't believe your newer fan setup had that aux temp sensor.
Racer
Joined: Jul 2002
Posts: 401
Likes: 1
From: Aptos CA
Re: Fan Control Question (VetNutJim)
Here is the correct info. A. Both fans are controlled by the ECM. B. Stock, there is no other fan control. C. There is a plug on the left side of the engine block were you can add an aftermarket thermostat and wire it into 2nd fan relay to turn on the fan earlier. It is sold as a kit.
I added this kit before my first custom chip from TPIS. I do my own chips, now. Therefore: I have cut the thermostat wire to the ADDED thermostat because I can set the 2nd fan to come on anytime I want.
"and that's the rest of the story" - Paul Harvey
I added this kit before my first custom chip from TPIS. I do my own chips, now. Therefore: I have cut the thermostat wire to the ADDED thermostat because I can set the 2nd fan to come on anytime I want.
"and that's the rest of the story" - Paul Harvey
Thread Starter
Safety Car
Joined: May 1999
Posts: 3,651
Likes: 5
From: Atlantis
Cruise-In I Veteran
Re: Fan Control Question (Skippy Stone)
Hey Paul Harvey, AKA Skippy Stone.
That coincides with what I have found by looking at the wiring diagrams.
I have a fan switch from MA or Ecklers or somebody and was going to install it last night.
There is just a plug where they said to put it between 1 and 3.
I already reprogrammed my PROM for lower turn on temps but got to wondering if the ECM used THAT temp probe for Fan 1 input.
Anyway I got to doubting what I thought I knew. :)
Your info is the complete unabridged edition. Good info.
I don't really need that switch on the 91.
Now where'd I leave that 84 Vette? Maybe IT need this switch.
That coincides with what I have found by looking at the wiring diagrams.
I have a fan switch from MA or Ecklers or somebody and was going to install it last night.
There is just a plug where they said to put it between 1 and 3.
I already reprogrammed my PROM for lower turn on temps but got to wondering if the ECM used THAT temp probe for Fan 1 input.
Anyway I got to doubting what I thought I knew. :)
Your info is the complete unabridged edition. Good info.
I don't really need that switch on the 91.
Now where'd I leave that 84 Vette? Maybe IT need this switch.
Thread Starter
Safety Car
Joined: May 1999
Posts: 3,651
Likes: 5
From: Atlantis
Cruise-In I Veteran
Re: Fan Control Question (VetNutJim)
Uh-oh another fan question.Or two. Mebe 3
Which fan is #1? Left or Right, from the drivers seat.
Which fan does the AC activate? #1 or #2
Which is 'primary' and which is 'secondary'??
Which fan is #1? Left or Right, from the drivers seat.
Which fan does the AC activate? #1 or #2
Which is 'primary' and which is 'secondary'??
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Racer
Joined: Jul 2002
Posts: 401
Likes: 1
From: Aptos CA
Re: Fan Control Question (VetNutJim)
Driver's side is #1 (primary). Ac turns on #1 (primary). #2 is ECM only when fan #1 can't keep the temp down and you need the extra fan. Hope this is what you needed.