98c5/a4 overheating
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From: Atlanta Ga.
Specifics please!!Does "still not working" mean the drivers side fan is still not running even at low speed????
When the engine begins to heat up does it VERY quickly go from cold to temperatures above 235???? Or does it go from cold to warm and after some time go to temperatures above 235??
When the gauge reads above 235 is the upper radiator VERY hot or just warm??
Is the coolant at the proper level as indicated by the mark on the end of the surge tank???
It goes from cold gradually(maybe 5-10 min.) to 220.. but it will hold at 220 as long as im moving.
when above 235 the upper radiator is very hot.. coolant is bubbling.
Coolant is at correct level.
Le Mans Master
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From: OK
I know this is super frustrating...
Did you pull any codes?
I believe BOTH fans should be running on LOW when temps reach 226
at 235 then BOTH fans should be running on HIGH
I don't think either the LOW or HIGH run at anything over 35 MPH..
Now the downside is I'm not the sharpest knife in the drawer, when it comes to the electrical...so, I THINK you will need the CODES to determine WHY the fans either the LOW or HIGH aren't coming on...
8vette7 and dadaroo will be able to help you with that part of the issue...
Did you pull any codes?
I believe BOTH fans should be running on LOW when temps reach 226
at 235 then BOTH fans should be running on HIGH
I don't think either the LOW or HIGH run at anything over 35 MPH..
Now the downside is I'm not the sharpest knife in the drawer, when it comes to the electrical...so, I THINK you will need the CODES to determine WHY the fans either the LOW or HIGH aren't coming on...
8vette7 and dadaroo will be able to help you with that part of the issue...
Last edited by 73Corvette; May 29, 2015 at 10:14 PM.
Le Mans Master
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From: OK
There is also this....as hot as your gauges are indicating you should be getting these messages and chimes?
COOLANT OVER TEMP The IPC illuminates the COOLANT OVER TEMP indicator in the message center when the following occurs:
• The PCM detects that the engine coolant temperature exceeds 124°C (256°F). The IPC receives a class 2 message from the PCM indicating the high coolant temperature.
• The IPC will also illuminate the CHECK GAGES indicator and a chime sounds when this condition exists.
COOLANT OVER TEMP The IPC illuminates the COOLANT OVER TEMP indicator in the message center when the following occurs:
• The PCM detects that the engine coolant temperature exceeds 124°C (256°F). The IPC receives a class 2 message from the PCM indicating the high coolant temperature.
• The IPC will also illuminate the CHECK GAGES indicator and a chime sounds when this condition exists.
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From: Atlanta Ga.
I know this is super frustrating...
Did you pull any codes?
I believe BOTH fans should be running on LOW when temps reach 226
at 235 then BOTH fans should be running on HIGH
I don't think either the LOW or HIGH run at anything over 35 MPH..
Now the downside is I'm not the sharpest knife in the drawer, when it comes to the electrical...so, I THINK you will need the CODES to determine WHY the fans either the LOW or HIGH aren't coming on...
8vette7 and dadaroo will be able to help you with that part of the issue...
Did you pull any codes?
I believe BOTH fans should be running on LOW when temps reach 226
at 235 then BOTH fans should be running on HIGH
I don't think either the LOW or HIGH run at anything over 35 MPH..
Now the downside is I'm not the sharpest knife in the drawer, when it comes to the electrical...so, I THINK you will need the CODES to determine WHY the fans either the LOW or HIGH aren't coming on...
8vette7 and dadaroo will be able to help you with that part of the issue...
Last edited by WHITLTNG; May 29, 2015 at 10:22 PM.
Le Mans Master
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From: OK
Chuck... he says his A/C isn't working... will the A/C NOT working have anything to do with the fans not working properly?
Even without the A/C working shouldn't he be able to turn the A/C switch on and see the fans come on?
Even without the A/C working shouldn't he be able to turn the A/C switch on and see the fans come on?
Last edited by 73Corvette; May 29, 2015 at 10:27 PM.
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From: Atlanta Ga.
I wished i knew how to read the diagram..
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Correct! AC has never worked Belt broke off after I bought it years ago.. never had any problems before.. even drag racing every weekend! Never over heated..
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Ive tried to switch on the AC button just to see if it would cut the fans on ---and nothing happens. neither fan comes on..
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Le Mans Master
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I will be lurking for moral support!
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From: Atlanta Ga.
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From: Atlanta Ga.
AC working or not has NO impact on Fan Operation. It is just easier to diagnose fan issues when the AC is working because the fans (BOTH) come on in low speed at 185 degrees and remain running until the coolant temp reaches 235 degrees.
Could you tell whether the passenger side fan was running at 230 degrees?
In low speed mode the fans are wired in series which means that about 1/2 of the 12 volts is dropped across each fan and hence they can only run at a speed decreased from full voltage speed. The wiring is reconfigured by the relays once the coolant reaches 235 degrees such that the fans are in parallel so that each fan has full battery voltage dropped across it so the speed is maximum.
Knowing if the passenger fan is running at less than 235 degrees and above 226 degrees is important in determining what is happening.
If neither fan runs in low speed mode tells me one thing but having the passenger fan running and NOT the drivers side fan tells me something else.
Is it possible to check the low speed operation at between 226 and 235 degrees?? Might take 2 people to do this. One in the car telling the other when the temp exceeds 226 and the other under the hood trying to determine what the fans are doing...
Since you tried swapping relays, can you please take a picture of the relays in the engine compartment fuse box and post it??? It is possible that you installed one or more relays incorrectly.. Picture can help eliminate that possibility.
Could you tell whether the passenger side fan was running at 230 degrees?
In low speed mode the fans are wired in series which means that about 1/2 of the 12 volts is dropped across each fan and hence they can only run at a speed decreased from full voltage speed. The wiring is reconfigured by the relays once the coolant reaches 235 degrees such that the fans are in parallel so that each fan has full battery voltage dropped across it so the speed is maximum.
Knowing if the passenger fan is running at less than 235 degrees and above 226 degrees is important in determining what is happening.
If neither fan runs in low speed mode tells me one thing but having the passenger fan running and NOT the drivers side fan tells me something else.
Is it possible to check the low speed operation at between 226 and 235 degrees?? Might take 2 people to do this. One in the car telling the other when the temp exceeds 226 and the other under the hood trying to determine what the fans are doing...
Since you tried swapping relays, can you please take a picture of the relays in the engine compartment fuse box and post it??? It is possible that you installed one or more relays incorrectly.. Picture can help eliminate that possibility.
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From: Atlanta Ga.
Cut corner of the 43 and 45 relays are both pointing in the same direction (toward the front of the car in your picture) so that is good.
But do you remember if before you swapped them if the cut corners were facing the battery??? ie could you hav turned them around 180 degrees when you reinstalled them?
But do you remember if before you swapped them if the cut corners were facing the battery??? ie could you hav turned them around 180 degrees when you reinstalled them?
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Ok,, because I didnt touch that one.. but like I was saying, I could have turned 43 and 45 around the wrong way, i do remember trying to keep them exactly like they came out..
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Please check fuses 49 and 14 in the engine compartment fuse box and let me know if either is blown. If either is blown do NOT replace it yet. Just post back the status here.
If we have anyone out there following this thread that has a 98 could you please check the orientation of the notch on relays 43 and 45 and post back here if the notch points toward the front of the car or toward the battery.
If we have anyone out there following this thread that has a 98 could you please check the orientation of the notch on relays 43 and 45 and post back here if the notch points toward the front of the car or toward the battery.
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Please check fuses 49 and 14 in the engine compartment fuse box and let me know if either is blown. If either is blown do NOT replace it yet. Just post back the status here.
If we have anyone out there following this thread that has a 98 could you please check the orientation of the notch on relays 43 and 45 and post back here if the notch points toward the front of the car or toward the battery.
If we have anyone out there following this thread that has a 98 could you please check the orientation of the notch on relays 43 and 45 and post back here if the notch points toward the front of the car or toward the battery.
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I redrew the wiring diagram with the 43 and 45 relays flipped 180. (not good any longer at just visualizing) It appears to me that if the relays were reversed that at least fuse #49 should have blown.
What we know is that the car runs at about 220 when you are moving along at speed above 35. When you stop or slow to below 35mph the car starts to heat up. The passenger side fan runs at high speed when the coolant temp is above 235 but the drivers side fan does not. Relays have been swapped ( 43 and 45) and that make no difference in the fan operation. Fuses are good. Uncertain if the passenger side fan comes on at coolant temp above 226 and below 235. Is it possible for you to determine the answer to this??
So what could prevent the drivers side fan from coming on.
One thing is that the PCM might not be closing the ground path to trigger relay 45. If that happens then NEITHER fan will run at low speed at coolant temps between 226 and 235.
Since this is an older car with the side post battery I ask that you check the PCM for indications of battery acid damage to the wiring. Easiest way is to remove the battery then remove the shelf the battery sits on. Below where the battery sits is the PCM and wiring for the PCM. If there is acid damage to the wiring we may have the answer.
What we know is that the car runs at about 220 when you are moving along at speed above 35. When you stop or slow to below 35mph the car starts to heat up. The passenger side fan runs at high speed when the coolant temp is above 235 but the drivers side fan does not. Relays have been swapped ( 43 and 45) and that make no difference in the fan operation. Fuses are good. Uncertain if the passenger side fan comes on at coolant temp above 226 and below 235. Is it possible for you to determine the answer to this??
So what could prevent the drivers side fan from coming on.
One thing is that the PCM might not be closing the ground path to trigger relay 45. If that happens then NEITHER fan will run at low speed at coolant temps between 226 and 235.
Since this is an older car with the side post battery I ask that you check the PCM for indications of battery acid damage to the wiring. Easiest way is to remove the battery then remove the shelf the battery sits on. Below where the battery sits is the PCM and wiring for the PCM. If there is acid damage to the wiring we may have the answer.
Ok, so treat me like a rookie here,, Im not sure where the "PCM" is!!
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Read the post you just quoted. PCM is directly below the battery. Two ways to gain access. One is to remove the battery and battery shelf and the other is to remove the passenger tire and then remove the plastic access panel on the back of the inner fender lining. Need long arms skinny arms for the access panel method to get at the wiring. 
The fans could have come on at 210 - 215 but only if a previous owner have the PCM reprogrammed to cause the fan turn on temp to be lower than 226. If that was done then the 210 - 215 may be the high speed turn on temp. With no AC to cause the fans to come on in low speed mode it looks like it is going to be difficult to know what happens at low speed turn on temp because we may not know what that is.
My fans are reprogrammed and the low speed turn on temp is set at 205 and the high speed turn on temp is set at 214. Might be the same on your car??
When you get a chance please check the wiring for the PCM to see if there is any acid damage.
One last question. When you replaced the drivers side fan motor did you make certain that you plugged back in the wiring harness?
The fans could have come on at 210 - 215 but only if a previous owner have the PCM reprogrammed to cause the fan turn on temp to be lower than 226. If that was done then the 210 - 215 may be the high speed turn on temp. With no AC to cause the fans to come on in low speed mode it looks like it is going to be difficult to know what happens at low speed turn on temp because we may not know what that is.
My fans are reprogrammed and the low speed turn on temp is set at 205 and the high speed turn on temp is set at 214. Might be the same on your car??
When you get a chance please check the wiring for the PCM to see if there is any acid damage.
One last question. When you replaced the drivers side fan motor did you make certain that you plugged back in the wiring harness?