Radiator Electric fan question - Chevy Impala SS Forum
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post #1 of 3 (permalink) Old 09-04-2017, 11:12 AM Thread Starter
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Question Radiator Electric fan question

One of the few concerns I had when inspecting my SS before buying was the previous owners 'off road adventure'. I have damaged wheel well trim, 2 dented rear quarters, and scratched up rear bumper. Added to this was an impact on the lower radiator support that dented in the metal cradle radiator shroud sits in that pushed the metal up into the pass side fan preventing it from rotating (see barn find thread for reference). Now that I'm driving the car and fixing what needs attention, I popped the hood after getting to work with the engine hot. Only the drivers side fan was spinning. Trying not to be a complete idiot, I reached in with a screw driver to spin the pass side fan manually. Sure enough it started spinning, but at only half speed? Is this normal? Are fans variable speed depending on temp?

I could hear a relay clicking under the hood from time to time, but no way to tell if it was just normal A/C or something else.
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post #2 of 3 (permalink) Old 09-04-2017, 11:41 AM
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the fans are not variable speed

From your description it sounds like the bent lower radiator well was pushed against the fan not allowing it to turn. If so and the relay for that fan kicks in the fan motor frozen by contact would burn up or the electrical circuit to it. The slower speed may be due to the motor overheating because it was being prevented to turn, if I understand your description correctly

You can buy replacement fan motors

Also pull each relay for the fans and check if the plastic base is melted where the pins go in and or the pins/base of the relay are burnt. GM had a TSB back when for the primary fan to relocate the relay out of the underhood fuse block. The secondary fan can also do this

Gary at innovativewiring.com has made a relay kit to resolve this if this is also part of your issue

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post #3 of 3 (permalink) Old 09-04-2017, 11:58 AM
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Thank Scott Mueller for the following:
"B/D-car LT1 (Caprice/Impala/Roadmaster/Fleetwood) Cooling Systems:

Standard equipment for all LT1 equipped B/D-cars is a dual electric fan setup with a 150-Watt primary (RH) fan and a 100-Watt secondary (LH) fan.

The electric engine coolant fans are independently operated by the Powertrain Control Module (PCM) based on the inputs from the Engine Coolant Temperature (ECT) sensor, AC Pressure Sensor, Vehicle Speed Sensor (VSS), and various other inputs.

The B/D-car coolant fans operate under PCM control at the following engine temperatures and A/C system pressures:

Fan ……………… Mode ……… Temp ………… A/C Pressure
Primary (RH)…ON…… 107°C / 225°F……225 psi
Primary (RH)…OFF……104°C / 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."

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