MG Sports Cars

engine swaps and other performance upgrades, plus "factory" and Costello V8s

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limey222
Michael Cubbon
Portland, OR
(129 posts)

Registered:
08/01/2015 12:55PM

Main British Car:
1969 MGB GM 3.4L V6

93-95 GM 3.4 PCM fan temperature values
Posted by: limey222
Date: October 14, 2015 01:30PM

Can anyone confirm that the stock PCM for these years sends a command to turn the fan on at 223 degrees F and back off at 185 degrees F?
I am reading this out of the 1994 GM factory Service manual (book 2 0f 2), am I interpreting this correctly?


Scott68B
Scott Costanzo
Columbus, Ohio
(541 posts)

Registered:
10/25/2007 11:30AM

Main British Car:
1968 MGB GM 5.3 LS4 V8

authors avatar
Re: 93-95 GM 3.4 PCM fan temperature values
Posted by: Scott68B
Date: October 14, 2015 06:22PM

Michael,

If you're using the PCM to control the fan it's an easy thing to confirm yourself with an infrared gun. The PCM takes feedback from the coolant temperature sensor and the GM CTS isn't known for being real accurate. Probably not a bad idea to check just so you'll know.


limey222
Michael Cubbon
Portland, OR
(129 posts)

Registered:
08/01/2015 12:55PM

Main British Car:
1969 MGB GM 3.4L V6

Re: 93-95 GM 3.4 PCM fan temperature values
Posted by: limey222
Date: October 15, 2015 02:33PM

Well i purchase an infrared gun and I wasn't far off. The electric fan definitely turns off around 185 F. The top limit for turning on was a bit sketchy, seems to be around 220 F even though the temp gage was reading around 225-230 F. Evans waterless coolant boils around 350+ F so the only concern would be oil temperature since I don't have an oil cooler installed.


MGBV8
Carl Floyd
Kingsport, TN
(3726 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: 93-95 GM 3.4 PCM fan temperature values
Posted by: MGBV8
Date: October 16, 2015 10:27AM

O course, that gun is only reading surface temps. Also, the the readings will be off based on what it is pointed at because of emissivity. Doesn't work as well on shiny objects. You can add a spot of flat black paint that can be cleaned off later.


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