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Cheap lower temp fan switch source

Joined
20 March 2008
Messages
1,434
Location
Colorado Springs, CO
I bought a Mugen lower temp fan switch only to find out that the NSX uses a different size switch than pretty much every other Honda ever. The Mugen switch is M18x1.5 while the NSX is M16x1.5. Once I found out the size I needed I started a search for a switch that would fit. That led me to a Mitsubishi sourced switch that turns on at 85 and shuts off at 80. So I went to pull apart today in search of one and found it in a 94 Mirage S, clipped the plug and pulled the switch, swapped it with the stock sensor, swapped the plugs, and it works perfectly. Kicks on right at 85c and shuts off right around 80 or so. Total money out of pocket, $5 for the part and $2 to go in to the pull apart yard, $7 total.

You can also get it brand new from any autoparts store for $20-25, it's Mitsu part number MB660663, but then you will have to find the plug somewhere.

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Here is a list of all the vehicles the switch can be found in according to Rock Auto. It's usually located in the bottom of the radiator next to the hose.

DODGE COLT (1993 - 1994)
DODGE COLT ES 1994
DODGE COLT GL 1993
DODGE STEALTH (1991 - 1996)
DODGE STEALTH ES (1991 - 1993)
DODGE STEALTH R/T (1991 - 1996)
DODGE STEALTH R/T SPORT (1994 - 1995)
DODGE STEALTH R/T TURBO (1991 - 1996)
EAGLE SUMMIT (1994 - 1996)
EAGLE SUMMIT DL (1994 - 1996)
EAGLE SUMMIT ES (1994 - 1996)
EAGLE SUMMIT ESI (1994 - 1995)
EAGLE SUMMIT LX (1994 - 1996)
MITSUBISHI 3000GT (1991 - 1993)
MITSUBISHI 3000GT SL (1991 - 1993)
MITSUBISHI 3000GT VR-4 (1991 - 1993)
MITSUBISHI DIAMANTE 1992
MITSUBISHI DIAMANTE ES (1993 - 1996)
MITSUBISHI DIAMANTE LS (1992 - 1995)
MITSUBISHI EXPO (1992 - 1995)
MITSUBISHI EXPO LRV (1992 - 1994)
MITSUBISHI EXPO LRV SPORT (1992 - 1994)
MITSUBISHI EXPO SP (1992 - 1993)
MITSUBISHI MIRAGE ES (1993 - 1995)
MITSUBISHI MIRAGE LS (1993 - 1995)
MITSUBISHI MIRAGE S (1993 - 1995)
PLYMOUTH COLT (1993 - 1994)
PLYMOUTH COLT GL (1993 - 1994)
PLYMOUTH COLT VISTA (1992 - 1994)
PLYMOUTH COLT VISTA SE 1992
 
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Can you explain the benefit of doing this? I really dont know, so im asking. Hope you Dont mind.
 
Can you explain the benefit of doing this? I really dont know, so im asking. Hope you Dont mind.

In theory it will help keep the coolant temps down a little bit by turning the fan on a good 10c sooner than stock.

Backstory:
Been chasing down a mild overheating issue at the track with my car, after checking all the minor stuff and bleeding the hell out of the coolant system I've decided to do some other cheap/simple stuff to see if I can get it to run a little cooler. I haven't had it on the track to see if it's helped since I've done this and the dual fans yet though, but since it was so cheap I figured I would share the info.
 
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In theory it will help keep the coolant temps down a little bit by turning the fan on a good 10c sooner than stock.

Backstory:
Been chasing down a mild overheating issue at the track with my car, after checking all the minor stuff and bleeding the hell out of the coolant system I've decided to do some other cheap/simple stuff to see if I can get it to run a little cooler. I haven't had it on the track to see if it's helped since I've done this and the dual fans yet though, but since it was so cheap I figured I would share the info.


Some overheating, as going a bar above the middle is normal on a track especially if you are on 2nd gear and shifting always at redline.

What dual fans are you using? Also, as an fyi, have you checked if the 30 amp fuse is enough for it? I took the advice of prime member and used 40 amp fuse for he was right, it blew the 30 amp fuse.
 
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Some overheating, as going a bar above the middle is normal on a track especially if you are on 2nd gear and shifting always at redline.

What dual fans are you using? Also, as an fyi, have you checked if the 30 amp fuse is enough for it? I took the advice of prime member and used 40 amp fuse for he was right, it blew the 30 amp fuse.

Yeah that's all it was doing, I searched around prime for a while and couldn't find anything saying that was normal. I have the dual mishimoto fans with shroud from dali racing. I will have to check the fuse today but so far it seems like the 30 amp is holding fine.
 
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I am not sure how you have messed up the stock NSX fan control system. The stock system uses a temp sensor and the fan control unit to control at what temp the fan starts and when it switches to high and when the AC compressor is disabled. The system is very capable of properly running the cooling fan with put being hacked up.
 
I am not sure how you have messed up the stock NSX fan control system. The stock system uses a temp sensor and the fan control unit to control at what temp the fan starts and when it switches to high and when the AC compressor is disabled. The system is very capable of properly running the cooling fan with put being hacked up.

It wasn't messed up at all, it's just a lower temp fan switch that will kick the fans on at 85c instead of 97c. This is basically just a cheaper version of the Buddy Club or Mugen fan switches, which I found out (after buying one) won't fit the NSX because it has a different sized fan switch than most other Hondas.
 
As I said the NSX has a temp sensor. Installing a switch in place of a sensor is just wrong and completely messes up a complex and elegant control system. You overheating issues are not caused by the fan not coming on soon enough or every NSX built would have that issue.
 
As I said the NSX has a temp sensor. Installing a switch in place of a sensor is just wrong and completely messes up a complex and elegant control system. You overheating issues are not caused by the fan not coming on soon enough or every NSX built would have that issue.

I have all of the NSX-R bits (hood, undertrays, radiator duct) as well as a Koyo radiator, so it's not exactly like every other NSX out there. I am also in Colorado with thinner drier air than most. (Pikes Peak hillclimb cars are even known to have cooling issues from the thinner high altitude air.)


After some experimenting I am fairly confident that my cooling issues are from a lack of airflow. Here is how I ended up at this conclusion. I bought a Mishimoto 60*c t-stat to test the theory and it the results seem to fit. Driving around my coolant temps would hover around 70-75*c depending on the ambient temperature (if it was really cold it would get to 60*c) and idling it would get up to the temp of the fan switch. To me, all else being healthy in the cooling system, that points to a lack of airflow. I would have most likely been just fine with the stock fan switch and the dual fans pushing more air, but turning on sooner won't hurt anything and gives it a bit of a jump at cooling things down. And the switch I put in is still above the temp of the stock t-stat so it's not like it will just sit there with the fans on non-stop.



Also, in Honda nomenclature the fan switch is listed as a sensor, but it is more of a switch than than a sensor as it is either on or off depending on the temp of the coolant. The "sensor" I replaced operates nothing other than the radiator fans anyways.

The NSX is just like any other Honda with 3 temp sensors:
-one for the ECU
-one for the dash gauge
-one for the fans

37750-PH2-014 THERMO UNIT
37760-PH7-003 SENSOR ASSEMBLY, RADIATOR FAN CONTROL
37870-PJ7-003 SENSOR ASSEMBLY, WATER TEMPERATURE
 
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Also, in Honda nomenclature the fan switch is listed as a sensor, but it is more of a switch than than a sensor as it is either on or off depending on the temp of the coolant. The "sensor" I replaced operates nothing other than the radiator fans anyways.

Again its not a switch and it does not operate in a on/off manner. It is a Thermistor, http://en.wikipedia.org/wiki/Thermistor.
Depending on the coolant temp measured by the sensor the fan control unit
turns on the fan on low and then high if necessary. It also cuts the ac compressor if the temp gets to high.
 
Fan is not going to help on the track. Airflow from the speed of the car is doing your cooling. Fan is there for when you don't have airflow, like stop and go traffic. If fact, the fan actually hurts airflow while the car is at speed.

See no fan. :)

nascar-driver-hits-coyote-at-190-mph.jpg
 
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Thanks Brian. You have been a HUGE asset here. The manual doesn't show me a good picture to see where the sensor is for me to measure the resistance, it looks to be up front somewhere.

The sensor on the engine on the thermo stat housing. It's a very low failure item. What kind of problem are you having ?
 
A bit more complicated since I'm using a K Series motor in my NSX, lol. Apparently the fan turns on around 183 degree which I thought was high but maybe not. I'm doing some more testing but so far it seems normal but I want to check the high fan status.

The sensor on the engine on the thermo stat housing. It's a very low failure item. What kind of problem are you having ?
 
A bit more complicated since I'm using a K Series motor in my NSX, lol. Apparently the fan turns on around 183 degree which I thought was high but maybe not. I'm doing some more testing but so far it seems normal but I want to check the high fan status.
I don't have my service manual handy but 183 sounds about right.
 
So i wanted to answer this issue as it applies to me a bit differently, the aem infinity actually controls my coolant fan input and turns it on at the specific temperature I tell it to. I pulled the resistor at the fan and jumped it with a wire and the fan speed didn't change so somehow the aem tells the oem nsx fan control unit to trigger HIGH fan when I request it.

The he AC fans on both sides work as normal when the AC runs they run, when I stop the AC, they stop. Turned out pretty good deal for me but I'll tell you, this nsx is tricky with all its computers.
 
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