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  #1  
Old 09-22-2007, 11:43 AM
1990 500SL
 
Join Date: Oct 2003
Location: Hawthorn Woods, IL. USA
Posts: 329
1990 500 Aux Fan Questions / Diag

Recently took the SL out on a long road trip.
Temp gauge sat at 80 +/- on the road.

In traffic it bumped up just above the line between the 80 and 120, I'll assume 100. Came down some when I started moving again.

I checked it when I arrived, still close to that 100 mark, but no aux fans running. Fuse is OK.

Searched here, not a lot of 129s with temp issue's.
Did see one that made me think they only run with the A/C.
Note my Climate Control is almost always in the EC Mode.
A/C kind meaningless if you never drive with the top up.

OK ??s
Will the fans run w/o A/C Running.
How can I check their operation ?
Where is the sensor and relay ?


Thanks
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1990 500SL

I was always taught to respect my elders.
I don't have to respect too many people anymore.
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  #2  
Old 09-22-2007, 12:27 PM
Mike Miller's Avatar
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Join Date: Sep 2005
Location: Huntington Beach, CA
Posts: 276
Quote:
Originally Posted by kknudson View Post
Recently took the SL out on a long road trip.
Temp gauge sat at 80 +/- on the road.

In traffic it bumped up just above the line between the 80 and 120, I'll assume 100. Came down some when I started moving again.

I checked it when I arrived, still close to that 100 mark, but no aux fans running. Fuse is OK.

Searched here, not a lot of 129s with temp issue's.
Did see one that made me think they only run with the A/C.
Note my Climate Control is almost always in the EC Mode.
A/C kind meaningless if you never drive with the top up.

OK ??s
Will the fans run w/o A/C Running.
How can I check their operation ?
Where is the sensor and relay ?


Thanks
The aux fans only run with the A/C on. They will keep your car running a little cooler in traffic. To check them, with the engine a running temp, turn on the A/C (Automatic) and wait. The sensor will turn them on.
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'92 MB 500 SL
'01 BMW 525i Sport
'98 Harley Davidson RoadKing
'74 BMW 3.0 CSi - Gone to a good home
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  #3  
Old 09-22-2007, 01:35 PM
1990 500SL
 
Join Date: Oct 2003
Location: Hawthorn Woods, IL. USA
Posts: 329
Thanks Mike.

Does the A/C have to actually be running.

ie ambient temp 80, CC set at 70.

Or is just having it "available" to run kick them on.
__________________
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1990 500SL

I was always taught to respect my elders.
I don't have to respect too many people anymore.
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  #4  
Old 09-23-2007, 11:44 AM
Mike Miller's Avatar
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Location: Huntington Beach, CA
Posts: 276
I think it has to run. The sensor needs to see the compressor working and heat build up on the low pressure side.
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'92 MB 500 SL
'01 BMW 525i Sport
'98 Harley Davidson RoadKing
'74 BMW 3.0 CSi - Gone to a good home
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  #5  
Old 09-23-2007, 11:51 AM
1990 500SL
 
Join Date: Oct 2003
Location: Hawthorn Woods, IL. USA
Posts: 329
OK Tkanks all.

And thanks to BobTerry who's post doesn't show.
But I got the Email Notification ?????

Here's what I got in the Email

---Quote (Originally by kknudson)---
Will the fans run w/o A/C Running.
---End Quote---
Yes!

---Quote (Originally by kknudson)---
How can I check their operation ?
---End Quote---
If you disconnect the leads from the A/C high-pressure switch located at the receiver/dryer and short them together, then the fans should switch-on provided the ignition is on.


---Quote (Originally by kknudson)---
Where is the sensor and relay ?
---End Quote---
The relay that switches power to the fans is among the relays and modules behind the fuses in the main fuse box. In addition to the high-pressure switch, the climate control unit will switch on the fans if the outside temperature is greater than 90 degrees or if the engine coolant reaches a high temperature.
***************
__________________
KLK, MCSE

1990 500SL

I was always taught to respect my elders.
I don't have to respect too many people anymore.
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  #6  
Old 09-23-2007, 12:00 PM
Mike Miller's Avatar
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Join Date: Sep 2005
Location: Huntington Beach, CA
Posts: 276
I knew there was someone smarter than I to give you the details. Also my thanks to BobTerry.
__________________
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'92 MB 500 SL
'01 BMW 525i Sport
'98 Harley Davidson RoadKing
'74 BMW 3.0 CSi - Gone to a good home
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  #7  
Old 09-23-2007, 04:02 PM
1990 500SL
 
Join Date: Oct 2003
Location: Hawthorn Woods, IL. USA
Posts: 329
missed something in my cut and paste from BobTerry


Fuse is OK.
---End Quote---
There are two fuses -- did you check both? One is located just above and behind the brake booster.


No I didn't know or check the second one, I'll do it shortly.

Thanks all
__________________
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1990 500SL

I was always taught to respect my elders.
I don't have to respect too many people anymore.
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  #8  
Old 09-24-2007, 09:26 PM
aam aam is offline
Registered User
 
Join Date: Sep 2006
Location: California
Posts: 115
Quote:
Originally Posted by kknudson View Post
OK Tkanks all.

And thanks to BobTerry who's post doesn't show.
But I got the Email Notification ?????

Here's what I got in the Email

---Quote (Originally by kknudson)---
Will the fans run w/o A/C Running.
---End Quote---
Yes!

---Quote (Originally by kknudson)---
How can I check their operation ?
---End Quote---
If you disconnect the leads from the A/C high-pressure switch located at the receiver/dryer and short them together, then the fans should switch-on provided the ignition is on.


---Quote (Originally by kknudson)---
Where is the sensor and relay ?
---End Quote---
The relay that switches power to the fans is among the relays and modules behind the fuses in the main fuse box. In addition to the high-pressure switch, the climate control unit will switch on the fans if the outside temperature is greater than 90 degrees or if the engine coolant reaches a high temperature.
***************
Like he said.
If you only want to test the fans.
Just short the wires on high/pressure switch color red with r 12 or green
with r 134 fans should run.
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