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The same thing happened last year and it was after dark,i pulled over in a parking lot and shut down the engine and lifted the hood and the fan was running at a very high speed for a few minutes like it should as i have read about to cool the engine down.That is when i had a new oem water pump,thermostat and new belt put on and all was good until 8/7 (My birthday).I went to renew my driver license at the DMV and it was hotter than hell out"113 degrees".I drove abou 3 miles and i temps started to climb very fast and i can not hear my fan running from inside the car,due to very loud exhaust.I pulled over and shut the engine off and lifted the hood and the fan was not running like it should of been,and i was getting all kinds of readouts in the DIC.It pooped out a good amount of my coolant mix.I was letting it cool down and a guy stopped and he had a gallon of good water and i added water and i was only two blocks from home.About 50' from home it shut down some of the injectors like it should.I pulled into the car port and let it cool down for a couple of hours,added more water and started it up and when my temp gets to 195 my fan should come on at 30% and 70% at 203,well that did not happen..First thing i did was to check the fuse with my meter it was good.More Later
You will have to get underneath the car and remove the connector and see what it looks like…this is what I found on a C6 a few years ago with cooling fan inop.
Ken, one easy thing you should check first. Make sure the fan can easily rotate. Wouldn’t be the first time some road debris got sucked up in there and jammed the fan. A plastic bag will do it nicely.
Did that and it is free.I drive on country roads at times and pick up all kinds of hay and dirt.Thinks for the hint Fats Waller...
You will have to get underneath the car and remove the connector and see what it looks like…this is what I found on a C6 a few years ago with cooling fan inop.
When the mobile mechanic gets here i will drive it up on my ramps and he will get under the vette and check the plug, and put 12 volts to the fan and see?? Thanks C5 diag....
Last edited by Cherokee Nation; Aug 12, 2024 at 05:01 PM.
Reason: add more
So you’re cruising at highway speeds, you turn on the AC, and the fan comes on? I don’t think so. The conditions as described in the document need to be met. It’s not like the AC button is an on/off switch for the fan. It’s not a reliable test of the rad fan.
Why disagree with me when I said EXACTLY the same thing you did in the post you quoted??....
Why disagree with me when I said EXACTLY the same thing you did in the post you quoted??....
My mistake. I quoted the wrong post (yours). I had occasion back in June to cold start the car with the hood up because I had just swapped out the alternator, and I wanted to make sure everything looked OK. Mind you, it took a couple of seconds to get out of the car to have a look The AC was switched on for sure, but the fan wasn’t running at that point. So as far as I’m concerned, it’s not a reliable way to force the fan on, whereas there is a way, as described above, to force the fan using a jumper arrangement.
My mistake. I quoted the wrong post (yours). I had occasion back in June to cold start the car with the hood up because I had just swapped out the alternator, and I wanted to make sure everything looked OK. Mind you, it took a couple of seconds to get out of the car to have a look The AC was switched on for sure, but the fan wasn’t running at that point. So as far as I’m concerned, it’s not a reliable way to force the fan on, whereas there is a way, as described above, to force the fan using a jumper arrangement.
If the temps were low when checking the fan yes it would not have come on but since the fan is VPW you won’t hear it running it’s so quiet at low speed…it’s not going to be roaring !!…did you visually check it ??
I did a visual check. AC runs ice cold, so I doubt I’m low on Freon or whatever is being used. Even though I’ve got a gauge to measure the pressure I’m reluctant to check it. Just my luck I’d start the Schrader valve leaking.
I did a visual check. AC runs ice cold, so I doubt I’m low on Freon or whatever is being used. Even though I’ve got a gauge to measure the pressure I’m reluctant to check it. Just my luck I’d start the Schrader valve leaking.
If you have a scan tool that can look at the AC Pressure Sensor data PID if it reads over 160 psi the fan should be running…you don’t need a gauge…no, don’t bother hooking up a manifold…high and low side pressures are dependent on outside air temp and humidity…at 243 psi my fan is running on cold start AC on.
The idea that turning on the AC forces the fan on is a myth. Attached is a GM document that describes the operation of the cooling system. There are a number of factors that determine if/when/at what duty cycle the fan runs. The whole idea is to run the fan at an appropriately speed and only when needed.
It does NOT have to be a Corvette shop…a mechanic well versed in electrical diagnostics which may be only 1 in a 100 or more and will be able to diagnose this …Corvettes don’t have magical electrical systems !!…I can diagnose anything electrical on a Corvette or on a Honda…if you know how a solenoid, thermistor, or a potentiometer operate they ALL basically operate the same way…if you have an auto electric shop in your area take it there.
It is a performance shop and they work on all muscle cars.same shop that worked on my vette.. C5 Diag....How to i report an up date on the post???
You will have to get underneath the car and remove the connector and see what it looks like…this is what I found on a C6 a few years ago with cooling fan inop.
C5 Dieg:My fan only goes to 70% at 203 degrees when it gets to 207 it will start dropping back down,and when it drops below 203 the fan runs at 30%.....That connected above was pulling a lot of current..Right
Was the AC on or off when you saw these numbers ??…did you get them from your mechanic or from you ???…when my AC was ON and ECT was 203 my duty cycle was 49%…with AC OFF it was 16% with high side pressure at 125 psi…the ECM uses the highest of either the ECT or AC high side pressure…someone had posted a chart in this thread…looking at the chart the high side pressure would have to be around 268 psi or so to see a 70% duty cycle…your ECT would have to be around 220 degrees to see 170 psi…if you are using that scan tool look at ECT in generic OBD2…there is something called “substituted values” which I won’t get into right now but in generic OBD2 whatever the ECM is seeing as an ECT will show accurately in generic….the DIC might show something different…the connector melts because there is a bad terminal connection like corrosion or bad “terminal tension” it’s called and that increased resistance causes heat and then the connection melts…I threw a lab scope on the control wire which is a “negative duty cycle” and I saw 10% that matched the scan tool…as duty cycle increases those square waves will get “wider” you can say !!…if you check the control wire with a DVOM you will see system voltage of 12.6 if battery is charged and will drop to around 7.5 volts or so when the AC is turned on.
Was the AC on or off when you saw these numbers ??…did you get them from your mechanic or from you ???…when my AC was ON and ECT was 203 my duty cycle was 49%…with AC OFF it was 16% with high side pressure at 125 psi…the ECM uses the highest of either the ECT or AC high side pressure…someone had posted a chart in this thread…looking at the chart the high side pressure would have to be around 268 psi or so to see a 70% duty cycle…your ECT would have to be around 220 degrees to see 170 psi…if you are using that scan tool look at ECT in generic OBD2…there is something called “substituted values” which I won’t get into right now but in generic OBD2 whatever the ECM is seeing as an ECT will show accurately in generic….the DIC might show something different…the connector melts because there is a bad terminal connection like corrosion or bad “terminal tension” it’s called and that increased resistance causes heat and then the connection melts…I threw a lab scope on the control wire which is a “negative duty cycle” and I saw 10% that matched the scan tool…as duty cycle increases those square waves will get “wider” you can say !!…if you check the control wire with a DVOM you will see system voltage of 12.6 if battery is charged and will drop to around 7.5 volts or so when the AC is turned on.
The tuner commanded my fan to come on sooner in 2009.
The tuner commanded my fan to come on sooner in 2009.
Well for whatever reason the cooling fan will have to be looked at…a scan tool with bidirectional capability can be used to turn it on….as I mentioned find an auto electric shop in your area…it is very easy to diagnose…BTW the fan shouldn’t come on when you disconnect the ECT..you will see -40 degrees or so….if you jumper the 2 wires the ECT will max out…be careful of some of the info you read on the Forum !!
Well for whatever reason the cooling fan will have to be looked at…a scan tool with bidirectional capability can be used to turn it on….as I mentioned find an auto electric shop in your area…it is very easy to diagnose…BTW the fan shouldn’t come on when you disconnect the ECT..you will see -40 degrees or so….if you jumper the 2 wires the ECT will max out…be careful of some of the info you read on the Forum !!
Very true on what we read on the interweb.I always use Mr Google first,then on this web. Note: The fan has been running like it should for a couple of days,with no labor and no bucks involved Will try to explain later....Ole farts like me can't word or type a reply on the complete problems and the code i had..
Very true on what we read on the interweb.I always use Mr Google first,then on this web. Note: The fan has been running like it should for a couple of days,with no labor and no bucks involved Will try to explain later....Ole farts like me can't word or type a reply on the complete problems and the code i had..
So the car has not been overheating as that was your original concern ??…and nothing was done with the car and everything is now OK ??
So the car has not been overheating as that was your original concern ??…and nothing was done with the car and everything is now OK ??
The car started to overheat on Aug 7th and i pulled over in a parking lot and the temp was at 268 and the dic was going nuts i shut it down and the fan was not running at all..I let it cool down and made it home (Two Blocks) then checked the fuse it was good...To make this short for now.I called the mobile tech,while i was waiting for him the following day i did the hard reset like Dano553 said a few times...Two hrs later i connected the battery and went around the block and back home and let it idle until it got to 195,then i shut it down and open the door and the FAN was running.I just had a new battery put in at autozone two days before the problem started...The code was P1258 also,that has been cleared.All ran fine until today eight days later.I drove down the blvd about a mile and my temp went to 214 and i pulled over and the fan was not running at all.A cel came on,i got my code reader and got code P0797 and P0700.I read about those codes,tranny (Auto) problems or maybe some other problems that i read about think i will put some C4 under it..Lol Sorry for the long reply.......Ken
