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Kozmob Samba Member
Joined: September 20, 2015 Posts: 25 Location: Washington
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Posted: Thu Sep 15, 2022 2:35 pm Post subject: Force radiator fan to cool transmission cooler |
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After some classic transmission issues, I had a transmission cooler installed on my ’99 EVC. According to my ScanGauge, the cooler doesn’t always keep the ATF cool. I travel a lot on Forest Service type roads - slow and steep – and the temp gets high; at times over 220. Slowing down doesn’t seem to help; I’m already going less than 25 mph; too slow apparently for airflow to cool the cooler.
I’ve tried running the AC to force the cooling fan to operate. The effect was minimal. I think the AC runs the low speed fan.
I’m considering adding a bypass switch to control the radiator cooling fan so it can be forced to operate when needed at low vehicle speeds. I would put something like a 10-minute timer on the switch to make sure it turns off. I would like to do a simple install at first just to test the concept. It seems like the easiest way would be to tap into the radiator temperature sensor switch on the side of the radiator, but I’m concerned that would confuse or damage the ECU.
Anybody here tried this? Any thoughts if I’m on the right track and/or ideas how to better do this?
Thanks / Kozmo
On a side note, going downhill doesn’t seem to result in cooler ATF. Is that because the transmission is still working; braking rather than powering the rig? |
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Joshwa Samba Member
Joined: November 18, 2015 Posts: 810 Location: North Seattle WA
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VolksVelo Samba Member
Joined: April 21, 2020 Posts: 138 Location: Portland, OR
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Posted: Thu Sep 15, 2022 5:00 pm Post subject: Re: Force radiator fan to cool transmission cooler |
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220° F + should still well within the safe operating range. |
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Kozmob Samba Member
Joined: September 20, 2015 Posts: 25 Location: Washington
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Posted: Thu Sep 15, 2022 6:20 pm Post subject: Re: Force radiator fan to cool transmission cooler |
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VolksVelo wrote: |
220° F + should still well within the safe operating range. |
I should have said "well over 220." It's gone to 240 several times before I was able to stop |
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mikemtnbike Samba Member
Joined: March 26, 2015 Posts: 2795 Location: North Carolina
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Posted: Thu Sep 15, 2022 7:53 pm Post subject: Re: Force radiator fan to cool transmission cooler |
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You could do this. Like 25 years ago I bypassed the relays in a 84 Wolfsburg rabbit convertible (great car) to a dash switch. I don’t remember all the details but I direct wired it to the battery with an inline fuse. Probably not the right way to do it but it worked for years and the factory system still worked too. I lived in phoenix and commuted in the car and wanted control.
Anyway, just saying, sure this is possible. _________________ 1991 Vanagon GL 2.1 AT Westfauxlia. "Frankie" Totaled https://www.thesamba.com/vw/forum/viewtopic.php?t=764510&highlight=carnage
1995 Eurovan Camper "Marzivan"
2020 GTI SE manual |
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subdewd Samba Member
Joined: January 16, 2018 Posts: 238
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Posted: Fri Sep 16, 2022 5:02 am Post subject: Re: Force radiator fan to cool transmission cooler |
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Yes, did this |
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almond Samba Member
Joined: April 06, 2021 Posts: 38
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Posted: Fri Sep 16, 2022 9:23 am Post subject: Re: Force radiator fan to cool transmission cooler |
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Do you have the transmission in D or in 2 when its getting that hot going 25 mph? |
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Kozmob Samba Member
Joined: September 20, 2015 Posts: 25 Location: Washington
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Posted: Sat Sep 17, 2022 10:02 am Post subject: Re: Force radiator fan to cool transmission cooler |
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subdewd wrote: |
Yes, did this |
Can you describe how you did this and how effective it was? |
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Kozmob Samba Member
Joined: September 20, 2015 Posts: 25 Location: Washington
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Posted: Sat Sep 17, 2022 10:05 am Post subject: Re: Force radiator fan to cool transmission cooler |
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almond wrote: |
Do you have the transmission in D or in 2 when its getting that hot going 25 mph? |
It gets hot regardless of the gear I'm in but I'm usually going slow enough that it's already in a low gear. I slow down and shift to a lower gear to help cool it thinking that the higher RPM is going to pump ATF faster.
It usually doesn't happen if I'm going over about 35 mph because I guess there is enough air flow to cool the cooler. |
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almond Samba Member
Joined: April 06, 2021 Posts: 38
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Posted: Sat Sep 17, 2022 6:52 pm Post subject: Re: Force radiator fan to cool transmission cooler |
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I thought the transmission was designed to lock in some way if you put it in a lower gear and not make as much heat vs leaving it in D. Page 85/86 of the manual kinda talks about changing the gear selector based on conditions. Maybe if you go into 2 before it overheats, it wont |
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EuroTec Samba Member
Joined: August 24, 2020 Posts: 382 Location: Asheville, North Carolina
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Posted: Sun Sep 18, 2022 5:31 am Post subject: Re: Force radiator fan to cool transmission cooler |
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Depending on how close the cooler is mounted to the AC condenser, it will have a hard time exchanging heat to the air when not moving.
Have you verified that you have enough transmission fluid after the cooler install? Might be a bit low for the extra volume needed.
Just a thought...
You could simply bypass the trigger wire from the cooling fan temperature switch to a switch mounted on the dash. Turn on the fan whenever you want. _________________ If it ain't broke, don't fix it! |
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Kozmob Samba Member
Joined: September 20, 2015 Posts: 25 Location: Washington
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Posted: Tue Sep 20, 2022 10:36 am Post subject: Re: Force radiator fan to cool transmission cooler |
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EuroTec wrote: |
Depending on how close the cooler is mounted to the AC condenser, it will have a hard time exchanging heat to the air when not moving.
Have you verified that you have enough transmission fluid after the cooler install? Might be a bit low for the extra volume needed.
Just a thought...
You could simply bypass the trigger wire from the cooling fan temperature switch to a switch mounted on the dash. Turn on the fan whenever you want. |
Thanks for your thoughts. I had my mechanic check the ATF level. It's good.
Bypassing the trigger wire is exactly what I want to do but I'm trying to confirm that it won't confuse the ECU. |
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subdewd Samba Member
Joined: January 16, 2018 Posts: 238
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Posted: Tue Sep 20, 2022 12:21 pm Post subject: Re: Force radiator fan to cool transmission cooler |
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It seems to help. Might just be placebo effect. But I use it preemptively in slow traffic or waiting.in line |
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