1990 Corvette Cooling Fans Not Kicking On
10-17-2013, 03:43 PM
#1
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1990 Corvette Cooling Fans Not Kicking On
Ok, if you have seen me post before I am asking a lot of questions as I chase down all the little things this 1990 Corvette I inherited needs. Now that it is running great, I have been taking it out a bit more. Got into some traffic today and realized the cooling fans are not kicking on. Can someone tell me the proper steps to diagnose the problem? Thanks. I am pretty sure it's not a fuse, they were all good the last time I was in there.
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Nilak (12-17-2023)
10-17-2013, 04:11 PM
#2
Race Director
First thing anybody is going to need to know, is how have you concluded that the fans are not working as designed?
At what temp have you let it get up too?
Not sure if your '90 has a digital temp gauge or now, but if so what temps are you seeing?
The factory analog (dial) gauge will cause you all kinds of grief and lead you to believing it is way too hot.
The factory settings for turning on the cooling fans is much higher than most people are used to seeing.
Since your a long time member though, I assume you already knew that.
Also if your A/C is in working order, by turning it on you should see the cooling fans (or at least one of them) come on.
At what temp have you let it get up too?
Not sure if your '90 has a digital temp gauge or now, but if so what temps are you seeing?
The factory analog (dial) gauge will cause you all kinds of grief and lead you to believing it is way too hot.
The factory settings for turning on the cooling fans is much higher than most people are used to seeing.
Since your a long time member though, I assume you already knew that.
Also if your A/C is in working order, by turning it on you should see the cooling fans (or at least one of them) come on.
10-17-2013, 06:55 PM
#6
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You are correct Rolla, I have been going by the factory analog gauge. It is usually no higher than midway between the 100 degree mark and the 260 degree mark, basically dead center on the gauge. Lately, it has been a little warmer and I was sitting in traffic and it seemed to be creeping pretty close to the upper range and the fan never came on. I have never witnessed it turn on. I inherited this vette and am chasing down so many problems. The AC doesn't seem to work either. The digital temperature control button in the car is very hard to get to go down. I have to press it over and over until I finally get it to move. Getting the temperature to go up is no problem. I let the car sit at idol until I saw the coolant temperature creeping up again and no fans. Not sure how to diagnose it.
On another note, I was chasing down a headlight problem and had to replace a broken fuseable link at the power block behind the battery. The headlights have brand new motors, but while they pop up when you turn them on, they won't go back down when you turn them off. I fixed the fuseable link and it didn't fix the problem, but was hoping it would fix the fans....no dice. Not sure what I fixed lol
On another note, I was chasing down a headlight problem and had to replace a broken fuseable link at the power block behind the battery. The headlights have brand new motors, but while they pop up when you turn them on, they won't go back down when you turn them off. I fixed the fuseable link and it didn't fix the problem, but was hoping it would fix the fans....no dice. Not sure what I fixed lol
10-17-2013, 07:07 PM
#8
Race Director
You are correct Rolla, I have been going by the factory analog gauge. It is usually no higher than midway between the 100 degree mark and the 260 degree mark, basically dead center on the gauge. Lately, it has been a little warmer and I was sitting in traffic and it seemed to be creeping pretty close to the upper range and the fan never came on. I have never witnessed it turn on. I inherited this vette and am chasing down so many problems. The AC doesn't seem to work either. The digital temperature control button in the car is very hard to get to go down. I have to press it over and over until I finally get it to move. Getting the temperature to go up is no problem. I let the car sit at idol until I saw the coolant temperature creeping up again and no fans. Not sure how to diagnose it.
As I mentioned, that analog gauge will drive you crazy.
First it does not have a linear scale. So, half way on the gauge isn't really the temp you might think.
As John A. Marker mentioned, the fans don't even come on until approx. 228°F.
At that temp, your analog gauge needle will be very close to the high side of the scale.
Look closely at the gauge, and you'll see a shaded area at the high end.
As long as the needle isn't actually into the shaded area, your car is not overheating.
Until you know what the actual temp. is, you don't really know if you have a fan issue or not.
And you can't tell what that temp is using the analog gauge.
10-17-2013, 07:24 PM
#9
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ok, noted Rolla. My problem is that I don't want to take to the edge of an over heat just to figure it out. Is there an easy separate gauge I can attach to figure it out? Seems strange that if it is just the gauge that I have never seen the fans come on, but I only got it home a few weeks ago and it's been cool here in the north east. With all the 35+ mph driving I do here it would stay cool anyway. I wish the AC worked.
The weird thing is that after I started it up cold after fixing the broken fusable link, I heard this strange period it whooshing sound and the idle wwould rise and fall. The clutch on the AC was periodically engaging and disengaging and then it finally just stopped. Not sure if it was related to the fusable link fix or not. I know I can't get it to work or engage at all with the controls in the car.
The weird thing is that after I started it up cold after fixing the broken fusable link, I heard this strange period it whooshing sound and the idle wwould rise and fall. The clutch on the AC was periodically engaging and disengaging and then it finally just stopped. Not sure if it was related to the fusable link fix or not. I know I can't get it to work or engage at all with the controls in the car.
10-17-2013, 07:35 PM
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Bill
10-17-2013, 07:41 PM
#12
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I have a new ecm chip for a 180 degree thermostat that kicks the fans on at 195 degrees I believe. I just won't install it until I see everything working properly first. Any help with this is appreciated...thanks Rolla so far.
10-17-2013, 08:22 PM
#13
You have not used a independent means ( say a IR gun ) to confirm what you are seeing on the gauge is actually what the engine temp is.
If the engine hasn't got to real 228 , then the fans will not have ever run
10-17-2013, 08:52 PM
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You are definitely right. I would just hate to find out with an overheat. The gauge was awfully close to that overheat zone on the gauge so it scared me. I will stop by a friend's shop tomorrow and see if he has an independent way to determine the temp.
10-18-2013, 10:00 AM
#16
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I am having more or less the same issue here in Texas on a '90 Vert I've owned for about a month (Vehicle History Report shows I'm the 8th owner).
I owned an '89 Vert back in the day ('90-95) and don't remember it running this hot, but at 51 I don't remember a lot of things....
My '90 analog temp gauge usually sits about 50-75% of travel but yesterday after some longer-than-usual cruising, while sitting in my driveway idling, it was sitting at 99% - right below the cross-hatched area. A/C was off and neither cooling fan ever came on.
Turned on the A/C and the temp needle dropped rather quickly into the "normal" range (50-75%) as the fans both came on.
Tried the A to B connection on the ALDL and sure enough the fans came on as Cliff H. suggests. Doesn't seem to be any issue with equipment or programming failures.
The cooling system is full of coolant and I do not notice any obvious leaks - my "simpler is better" diagnosis is that the sender is a little off, perhaps mis-calibrated, perhaps old, perhaps the signal is not getting transmitted very well through the 25 year old wire that sits right next to the passenger side exhaust manifold. Reasoning: On cold starts, the temp needle is just a bit above the 100 degree mark, while the oil temp needle is buried well below the 100 degree mark.
My repro '90 owner's manual says that as long as the needle isn't in the cross-hatched area you're good to go. While very close, mine was not there. It also suggests that as long as there is no steam coming from under the hood, everything is "probably" OK.
Yes, I could buy a kit to make the fans come on sooner, or wire a manual switch, or re-program the ECM (and I may do any or all at a later date) but for now if I can't stand the temp needle being where it is I'll just select "Auto" on the A/C or remind myself that this is a very common issue. It doesn't sound like I'm doing any actual damage to the engine, and as reassurance, the oil temp is always in the comfortable range during these episodes.
I owned an '89 Vert back in the day ('90-95) and don't remember it running this hot, but at 51 I don't remember a lot of things....
My '90 analog temp gauge usually sits about 50-75% of travel but yesterday after some longer-than-usual cruising, while sitting in my driveway idling, it was sitting at 99% - right below the cross-hatched area. A/C was off and neither cooling fan ever came on.
Turned on the A/C and the temp needle dropped rather quickly into the "normal" range (50-75%) as the fans both came on.
Tried the A to B connection on the ALDL and sure enough the fans came on as Cliff H. suggests. Doesn't seem to be any issue with equipment or programming failures.
The cooling system is full of coolant and I do not notice any obvious leaks - my "simpler is better" diagnosis is that the sender is a little off, perhaps mis-calibrated, perhaps old, perhaps the signal is not getting transmitted very well through the 25 year old wire that sits right next to the passenger side exhaust manifold. Reasoning: On cold starts, the temp needle is just a bit above the 100 degree mark, while the oil temp needle is buried well below the 100 degree mark.
My repro '90 owner's manual says that as long as the needle isn't in the cross-hatched area you're good to go. While very close, mine was not there. It also suggests that as long as there is no steam coming from under the hood, everything is "probably" OK.
Yes, I could buy a kit to make the fans come on sooner, or wire a manual switch, or re-program the ECM (and I may do any or all at a later date) but for now if I can't stand the temp needle being where it is I'll just select "Auto" on the A/C or remind myself that this is a very common issue. It doesn't sound like I'm doing any actual damage to the engine, and as reassurance, the oil temp is always in the comfortable range during these episodes.
10-18-2013, 11:30 AM
#17
Drifting
The gauge in the dash reads from a different sensor than the one the ecm reads from for fan control. You may do the simple tests shown above, and or put the programming in you mentioned. It is set at 200 on, and 190 off.
10-18-2013, 12:21 PM
#18
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In order to connect the A and B to see if the fan comes on, am I just using a wire to connect A and B pins on the ALDL connector? Which pins are they?
10-18-2013, 01:23 PM
#20
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Ok, thanks Mr ******. When I connect the A and B pins on the ALDL connector only the lower passenger side fan is coming on. The upper, drivers side fan is not. 1. I don't know that the lower one is coming on when it needs to even though it appears to be working, but it was so quiet ( did it with the key on, motor off) I am not sure I would notice it. And 2. I am not sure of the steps to now take to fix the one that is not turning on. I can follow directions if someone can give them...Thanks