Another C4 Cooling Fan Problem
Thread Starter
3rd Gear
Joined: Jan 2004
Posts: 3
Likes: 0
From: Clermont Fl
Another C4 Cooling Fan Problem
1991 - L98
If anyone could help, it would greatly be appreciated.
I am having problems with my Primary Cooling Fan. It will not come on when the engine heats up. The Secoundary Cooling Fan comes on at about 235*.
I have grounded the OB Dionostic Terminal A to B, both fans run.
I replaced both relays, the Temp Switch and the temp Sender Switch. ( Still nothing ) I have even replaced the ECM. If I disconnect the Temp Switch, the Primary Fan runs with a service engine light. ( I assume that is becuase of the system fault override.)
I really do not want to put a manual fan switch in.......
Question 1: If the wiring to the Temp Switch was bad , could this cuase the problem without setting any codes?
Question 2: If the Fan Motor was bad running a higher resistance then it should be, would it work grounding it and not with the relay?
Any Ideas? I'm at a loss!
DHS91vette
[Modified by DHS91vette, 8:05 PM 1/10/2004]
[Modified by DHS91vette, 9:50 PM 1/10/2004]
If anyone could help, it would greatly be appreciated.
I am having problems with my Primary Cooling Fan. It will not come on when the engine heats up. The Secoundary Cooling Fan comes on at about 235*.
I have grounded the OB Dionostic Terminal A to B, both fans run.
I replaced both relays, the Temp Switch and the temp Sender Switch. ( Still nothing ) I have even replaced the ECM. If I disconnect the Temp Switch, the Primary Fan runs with a service engine light. ( I assume that is becuase of the system fault override.)
I really do not want to put a manual fan switch in.......
Question 1: If the wiring to the Temp Switch was bad , could this cuase the problem without setting any codes?
Question 2: If the Fan Motor was bad running a higher resistance then it should be, would it work grounding it and not with the relay?
Any Ideas? I'm at a loss!
DHS91vette
[Modified by DHS91vette, 8:05 PM 1/10/2004]
[Modified by DHS91vette, 9:50 PM 1/10/2004]
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Re: Another C4 Cooling Fan Problem (DHS91vette)
1991 - L98
If anyone could help, it would greatly be appreciated.
I am having problems with my Primary Cooling Fan. It will not come on when the engine heats up. The Secoundary Cooling Fan comes on at about 135*.
I have grounded the OB Dionostic Terminal A to B, both fans run.
I replaced both relays, the Temp Switch and the temp Sender Switch. ( Still nothing ) I have even replaced the ECM. If I disconnect the Temp Switch, the Primary Fan runs with a service engine light. ( I assume that is becuase of the system fault override.)
I really do not want to put a manual fan switch in.......
Question 1: If the wiring to the Temp Switch was bad , could this cuase the problem without setting any codes?
Question 2: If the Fan Motor was bad running a higher resistance then it should be, would it work grounding it and not with the relay?
Any Ideas? I'm at a loss!
DHS91vette
Modified by DHS91vette, 8:05 PM 1/10/2004]
If anyone could help, it would greatly be appreciated.
I am having problems with my Primary Cooling Fan. It will not come on when the engine heats up. The Secoundary Cooling Fan comes on at about 135*.
I have grounded the OB Dionostic Terminal A to B, both fans run.
I replaced both relays, the Temp Switch and the temp Sender Switch. ( Still nothing ) I have even replaced the ECM. If I disconnect the Temp Switch, the Primary Fan runs with a service engine light. ( I assume that is becuase of the system fault override.)
I really do not want to put a manual fan switch in.......
Question 1: If the wiring to the Temp Switch was bad , could this cuase the problem without setting any codes?
Question 2: If the Fan Motor was bad running a higher resistance then it should be, would it work grounding it and not with the relay?
Any Ideas? I'm at a loss!
DHS91vette
Modified by DHS91vette, 8:05 PM 1/10/2004]
Jake
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: Another C4 Cooling Fan Problem (DHS91vette)
Q1. If the wiring from the temp sender was bad, then a code would be set because the ECM relies on the temp sender not only for the fan, but also for other engine functions.
Q2. The fan motor receives 12v through the fan relay contacts. The fact that the fan runs when you jump ALDL A toB shows that the fan motor is not the problem, nor is the relay.
The main fan should come on at 228F and the auxiliary fan at 238 F. You may have a coolant sensor that is now defective and there is a cooling fan diagnosis procedure in the GM service manual (not the electrical manual). Maybe a CFer can post the procedure. My money is on a defective coolant temp sender.
[Modified by jfb, 9:04 PM 1/10/2004]
Q2. The fan motor receives 12v through the fan relay contacts. The fact that the fan runs when you jump ALDL A toB shows that the fan motor is not the problem, nor is the relay.
The main fan should come on at 228F and the auxiliary fan at 238 F. You may have a coolant sensor that is now defective and there is a cooling fan diagnosis procedure in the GM service manual (not the electrical manual). Maybe a CFer can post the procedure. My money is on a defective coolant temp sender.
[Modified by jfb, 9:04 PM 1/10/2004]
Thread Starter
3rd Gear
Joined: Jan 2004
Posts: 3
Likes: 0
From: Clermont Fl
Re: Another C4 Cooling Fan Problem (jfb)
When you say Coolant Temp Sender, you mean : Passenger side ,block below the #6 plug, single wire, runs your temp guage? I have replaced it.
Is there another switch?
Is there another switch?
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
Le Mans Master
Joined: Aug 2003
Posts: 9,884
Likes: 3
From: Magnolia Mississippi
St. Jude '03-'04-'05-'06-'07
Re: Another C4 Cooling Fan Problem (DBLAZER4)
ski_dwn_it@yahoo.com burns custom proms and is real good. send him an email and he will give you the info you need
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Re: Another C4 Cooling Fan Problem (DHS91vette)
Hope you're not confusing the main with aux fan or that somehow the wiring for both got switched. When the aux fan comes on, does the temp drop?Parameters for fan operation is 226 main (a/c off) and 228 aux. The gauge relies on a different signal and it's not unusal for it read higher due to inaccuracy and the fact it's signal is from a sender in the right head. To determine if the main fan is working correctly, you need to see what temp the coolant temp sensor (below the throttle body) is indicating with a scanner. If it's out of range, it won't generate a code, but it will - as you found out - if the circuit is open. When the engine is cold, it should read close to ambient and if the aux fan is coming on, it should be indicating 228 or above (enough for main fan operation). Regardless of temp, main fan (and on some years the aux fan too - I can't remember when it changed) should come on with the a/c on, with a high side pressure of 233 psi. A manifold gauge set is needed to check this, but you can do a quick check by disconnecting the fan switch on the high pressure line which should turn it on.
Drifting
Joined: Jun 2000
Posts: 1,955
Likes: 2
Re: Another C4 Cooling Fan Problem (DHS91vette)
Did the problem start before or after you replaced the sending unit/switch? I have heard of a lot of problems with replacement switches that were incorrectly calibrated.
