HD Cooling - Chevy Impala SS Forum
 
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post #1 of 8 (permalink) Old 09-06-2015, 07:28 PM Thread Starter
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HD Cooling

Is the electrical secondary fan for a/c or is it a cooling fan that comes on by its self?
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post #2 of 8 (permalink) Old 09-06-2015, 07:58 PM
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The right fan should come on with the AC, and the left fan comes on with water temp.

1991 OCC 461 (.030 over 454) BBC, 3.23 posi, flash to pass, drop spindles & springs, Impala rims, Hydroboost, Recaros, MOMO/wood SW w/QR, custom wood shift knob, Pioneer DEH P77DH
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post #3 of 8 (permalink) Old 09-06-2015, 09:49 PM
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HD Cooling = mechanical fan + electric fan, right?

Jim B.

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post #4 of 8 (permalink) Old 09-06-2015, 10:50 PM
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With AC off, the secondary will also run when temps are hot enough.

grandpas wagon
1994 RMW 80K, clear corners, Gary's cables - battery, headlight, mech fan delete, air pump delete, home plate/first base delete, Bill Harper wiper arm mod, Corvette starter, 1LE elbow, Team SS pipe, K&N filter swiss cheese airbox, throttle body bypass, LED headlights.

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post #5 of 8 (permalink) Old 09-07-2015, 02:44 AM
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Scott Mueller's answer has not really been improved upon since the late 90s.
Quote:
Originally Posted by Scott Mueller
B- & D-car coolant fans operate under PCM control at the following H2Opump temperatures and A/C system pressures:

Fan ……………… Mode ……… Temp ………… A/C Pressure
Primary (RH)…ON…… 107°C or 225°F……225 psi
Primary (RH)…OFF……104°C or 219°F……180 psi
2ndary (LH)……ON…… 111°C & 232°F……248 psi
2ndary (LH)……OFF……107°C & 225°F……203 psi

Additionally, the PCM will turn off the fans at higher vehicle speeds (above 48 MPH I believe), since running fans can actually impede airflow through the radiator at high speed.
Each fan also has a minimum running time. Once activated, the primary fan will run for a minimum of 50 seconds, and the secondary fan for a minimum of 26 seconds.
Finally, certain Diagnostic Trouble Codes (DTCs) may cause the PCM to turn on one or both fans.
Cars with RPO V08 have a [primary mechanical fan, and a] secondary electrical fan which behaves exactly as spec'd above; I.E.:
'ON' @ 232°F or 248psi (whichever happens 1st)
'OFF' @ 225° AND 203psi (must be under BOTH)

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post #6 of 8 (permalink) Old 09-07-2015, 02:58 PM Thread Starter
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Does primimary mechanical fan have a clutch or does it run when ever engine is running?
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post #7 of 8 (permalink) Old 09-07-2015, 03:07 PM
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Quote:
Originally Posted by Dutchess B Body View Post
Does primimary mechanical fan have a clutch or does it run when ever engine is running?

It has a clutch - it freewheels when over a certain speed - IIRC 45 or so. Do yourself and your car a favor and do a mech fan delete.

grandpas wagon
1994 RMW 80K, clear corners, Gary's cables - battery, headlight, mech fan delete, air pump delete, home plate/first base delete, Bill Harper wiper arm mod, Corvette starter, 1LE elbow, Team SS pipe, K&N filter swiss cheese airbox, throttle body bypass, LED headlights.

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post #8 of 8 (permalink) Old 09-28-2015, 02:50 AM
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Adjust fan turn on temps

I didn't like how hot the PCM allowed the engine to get before it turned on the fans, so I used Tuner Cat to edit the turn on temps in the PCM so that the primary turned on at 205*F and off at 200*F. I set the secondary to turn on at 210*F and off at 205*F.

FWIW and YMMV.

BTW, I have a NIB GM 3.42 ring and pinion I bought just before our 1995 Roadmaster got totaled. Doesn't take much to total an eleven year old car with 148,000 miles. PM me if anyone is interested. Also have the Owner's Manual and blue vinyl folder, five alloy wheels and center caps.

95 9C1, Sold 2009, 203K miles, PCM by Me and Tuner Cat, Meziere water pump, Roadmaster blue leather interior

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95 Roadmaster, totaled 2006, 148K miles, 9C1 suspension, Bilstein 1516/1517's, PCM by Me and Tuner Cat, Meziere water pump
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Last edited by Rowland Hill; 09-28-2015 at 02:55 AM.
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