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radiator fan problem - i searched also!

iornman86
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iornman86 Member

iornman86

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ok so i have noticed in the summer my temperature is fairly high, cleaned out the radiator area this weekend via the bumper removal. I am using the climate control hack to view the engine temperatures. If i drive in stop and go traffic temperatures get up to 109 c. the radiator fans are not turning on.

with the a/c turned on the fans kick on. I have tested all of the relays with the ac on to verify all the relays are working. without the ac on the fans do not turn on low speed when it surpasses 98 c, nor does it turn on high speed when it surpasses 102c.

i know both the fans are good because the kick on very strong with ac on, in fact the car runs cooler with ac on because the fans are running, what could be causing this?

i have not checked the resistors, but regardless of their status they should be kicking on high speed when it surpasses 102 c correct?

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BruceP Member

BruceP

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ok so i have noticed in the summer my temperature is fairly high, cleaned out the radiator area this weekend via the bumper removal. I am using the climate control hack to view the engine temperatures. If i drive in stop and go traffic temperatures get up to 109 c. the radiator fans are not turning on.

with the a/c turned on the fans kick on. I have tested all of the relays with the ac on to verify all the relays are working. without the ac on the fans do not turn on low speed when it surpasses 98 c, nor does it turn on high speed when it surpasses 102c.

i know both the fans are good because the kick on very strong with ac on, in fact the car runs cooler with ac on because the fans are running, what could be causing this?

i have not checked the resistors, but regardless of their status they should be kicking on high speed when it surpasses 102 c correct?

Not necessarily, I don't believe. There are separate resistors low speed and high speed fan operation, and for each side. I had a similar problem, only I was getting fan operation on the right but not the left. This was the checklist of fan-related problems I put together with help from this forum, from easiest/cheapest to hardest/most expensive:

Fuses. There is a fuse for the left and one for the right.

Relays. There are separate relays for each side, and for high and low speed fan operation. In other words, four of them.

Ballast resistors. Can become corroded, apparently, and the dealer tech claimed that such corrosion could leave you with partial fan operation.

The fan itself. In my case, this was the problem. The whole thing just gave out.

What's strange to me is that you're having trouble with both of them at the same time, but I know it's possible for a fan to fail in this way. Mine did. I was getting low speed operation only from the left side and both speeds on the right. So you may not want to assume the fans are fine just because they work at low speed.

Anyway, consider this a courtesy bump. I'm sure someone who knows what they're talking about will chime in.

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perryinva Member

perryinva

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Wow, that's a tough one. Check this. With the AC on, but you hand NEAR the ballast resistor behind each fan. Easy to see, about the size of a cigar with 3 wires coming from it. In front of the wheel well, but behind the fan. They should be HOT. If they are, then your fans are operating properly at low speed from the AC trigger. If not hot, then they are running at high speed, and you have a bigger problem. I know Dallas is hot, but we've been at 100+ for the last few days and with my Autoenginuity software, I've been monitoring my coolant temp. With my AC off and just driving spiritedly with revs in the 5k range, I had to WORK to get the temp up to 205F (96C). I had to abruptly stop the car in direct sunlight on black asphalt to get the fans to kick in on low speed, and even then, they only went on for like 20 seconds. Becuase they don't not work at either temperature, I'd suspect the coolant temperature sensor. I don't know if the sensor for reading the temp in the HVAC hack is the same one used for the fan control. It's not the relays, as the low speed/AC ones are the same and they obviously work. BOTH high speed ones would have be bad, in you case..unlikely. Maybe there is a different fuse for the fans, but I'd be shocked if they ALL went. Fuses are easy to check. Drivers footwell left side.. Hate to say it but I'd get the Durametric software, which allows you to switch them on through the computer and diagnose it that way. Cheaper than taking it to the dealer and you'll have the software to use over & over again. 109 is very hot, but not dangerous hot (228F). What is the coolant temp with AC on? Mine is 192-4 F (89-90C) with 100F outside temp around town, 190F on the interstate. Seems to me you ARE running too hot, so maybe Tstat? But doesn't explain the fans. Mines an 02 C2, which tend to run cooler than the 3.4's, from what I've read.

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iornman86 Member

iornman86

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Wow, that's a tough one. Check this. With the AC on, but you hand NEAR the ballast resistor behind each fan. Easy to see, about the size of a cigar with 3 wires coming from it. In front of the wheel well, but behind the fan. They should be HOT. If they are, then your fans are operating properly at low speed from the AC trigger. If not hot, then they are running at high speed, and you have a bigger problem. I know Dallas is hot, but we've been at 100+ for the last few days and with my Autoenginuity software, I've been monitoring my coolant temp. With my AC off and just driving spiritedly with revs in the 5k range, I had to WORK to get the temp up to 205F (96C). I had to abruptly stop the car in direct sunlight on black asphalt to get the fans to kick in on low speed, and even then, they only went on for like 20 seconds. Becuase they don't not work at either temperature, I'd suspect the coolant temperature sensor. I don't know if the sensor for reading the temp in the HVAC hack is the same one used for the fan control. It's not the relays, as the low speed/AC ones are the same and they obviously work. BOTH high speed ones would have be bad, in you case..unlikely. Maybe there is a different fuse for the fans, but I'd be shocked if they ALL went. Fuses are easy to check. Drivers footwell left side.. Hate to say it but I'd get the Durametric software, which allows you to switch them on through the computer and diagnose it that way. Cheaper than taking it to the dealer and you'll have the software to use over & over again. 109 is very hot, but not dangerous hot (228F). What is the coolant temp with AC on? Mine is 192-4 F (89-90C) with 100F outside temp around town, 190F on the interstate. Seems to me you ARE running too hot, so maybe Tstat? But doesn't explain the fans. Mines an 02 C2, which tend to run cooler than the 3.4's, from what I've read.

well i know the fans are working, because of the ac. when it goes over 102 the high speed fans should be on so it takes the resistor out of the picture for me, neither side works on low or high speed when completely dependent on coolant temperature. the only thing that would make sense is if the hvac is on a different sensor than the fans, however i would think that would throw a code....

when i see the temperature get to 105c on the hvac in stop and go traffic i can turn the ac on and it drops down to 98c or so

just for the record i have a 3.4l 1999 c2

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iornman86 Member

iornman86

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The best way to check the fans is the runs the tests in a PST2 or PIWIS tester.

That would confirm whether it is a fan (ballast, relay) problem or a stuck thermostat.

well if it were a relay wouldn't the ac have trouble with the fans as well? if the fans worked in high speed just not low speed wouldn't that point to the ballast?

is it a different sensor that causes th fans to kick on vs the hvac hack readout?

is there is something else that would prevent the fans to work? something that the ac system would bypass?

edit : i just searched and the only temperature sensors on the car i can find are the temp sensor on the bumper (for external temperatures), the temperature sensor for the hvac controller ( to adjust the cabin heater/cooler), the one on the intake ( for engine bay temperatures) and the temp sensor on the oil pump (actual engine temperature)

so i guess i need to monitor the voltage on the relay pin vs th ecu to see if there is voltage being sent to the relay. i guess if it is not sending any voltage to the relay then it is a ecu problem, if it is and not reaching the relays then it is a wiring problem. i don't see the wiring for both he high speed and low speed havening issues unless ig somehow got pinched when i was pulling wires for the stereo.....

Edited by iornman86
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Loren Member

Loren

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The best way to check the fans is the runs the tests in a PST2 or PIWIS tester.

That would confirm whether it is a fan (ballast, relay) problem or a stuck thermostat.

well if it were a relay wouldn't the ac have trouble with the fans as well? if the fans worked in high speed just not low speed wouldn't that point to the ballast?

is it a different sensor that causes th fans to kick on vs the hvac hack readout?

is there is something else that would prevent the fans to work? something that the ac system would bypass?

There are 4 relays for the fans on a 996.

1 each for low speed and 1 each high speed on each side.

post-1-1213322542_thumb.png

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iornman86 Member

iornman86

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There are 4 relays for the fans on a 996.

1 each for low speed and high speed on each side.

yes i realize that, i pulled all 4 turned on the ac and tested each one individually in one of the high speed slots to verify they worked, i also edited my post above

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  • 2 years later...
mcneil141 Member

mcneil141

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Hello,

Was there a solution for this? I am experiencing the same problem with a 2001 C2. The car is overheating and the fans are not running, that is, unless the A/C is on. If the A/C is on, the fans work fine. My technician suspects the ECU is problematic.

Any experience with this?

TIA,

Andy

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Loren Member

Loren

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Hello,

Was there a solution for this? I am experiencing the same problem with a 2001 C2. The car is overheating and the fans are not running, that is, unless the A/C is on. If the A/C is on, the fans work fine. My technician suspects the ECU is problematic.

Any experience with this?

TIA,

Andy

Check C10 and C8 for blown fuses - both should be 40 A.

Test the relays (all 4 of them) and the two ballast resistors.

Highly unlikely (IMHO) that the DME is the problem - besides you really don't want to spend $1700 for a DME - plus programming time.

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fbgh2o Member

fbgh2o

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the fans do not turn on low speed when it surpasses 98 c, nor does it turn on high speed when it surpasses 102c.

I have been trying to figure this out all summer. The low speed fans come on at 100C and the high speed at 105C on some cars. I know of several people with early 996 who have reported these numbers and who can show factory manuals that indicate same. I can confirm that my fans are working fine and that the temperatures are confirmed via a Durametric at 100C and 105C. Also if you are using the climate control hack to monitor temperatures, it is off by as much as 3.5C. Mine shows as high as 103C when the Durametric shows 99.5C.

I also know that there are posts here to the contrary. In fact, Loren has a different set of numbers; 98C and 102 IIRC, so I am quite confused.

All that to say if your fans are working the way that you indicate, it seems like something is wrong....

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Loren Member

Loren

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Hello Loren,

The fuse and relays check out fine. I am going to check the ECU output for the fans. Any recommendation for ECU repair?

Thanks again,

Andy

Check C10 and C8 for blown fuses - both should be 40 A.

Test the relays (all 4 of them) and the two ballast resistors.

Highly unlikely (IMHO) that the DME is the problem - besides you really don't want to spend $1700 for a DME - plus programming time.

I REALLY don't think it is your DME.

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