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At what temp does the electric fan come on?

Well, for what it is worth the FSM 90 says it should come on when the coolant temperature is above 190 degrees F the switch should close and the fan operate. Page 7-29.
 
ehall said:
Interestingly the 91 FSM says that the computer grounds the relay when engine temperature reaches 190f, however that is not the observed behavior -- mine comes on around 220
Click to expand...

Kinda weird--190 degree fan switch, 195 degree thermostat?
 
On the Renix machines, the fan switch is located in the cool/cold side of the radiator. The engine temperature sender is in the hot side of the engine I am sure one can see a very high engine temperature before the electric fan come on.

On my 1996 ODB2, the engine temperature reaches 230 before the PCM turn the electric fan on.
 
RCP Phx said:
Radiator temp and engine temp are 2 different things!
Click to expand...

Perfect.

That is why I use a temperature switch of 185* on and 170* off in the radiator outlet (bottom hose) to turn on the electric fans. The fans now come on when the engine temperature is 215*. The PCM controlled fan switch never come on.
 
techno1154 said:
On the Renix machines, the fan switch is located in the cool/cold side of the radiator. The engine temperature sender is in the hot side of the engine I am sure one can see a very high engine temperature before the electric fan come on.

On my 1996 ODB2, the engine temperature reaches 230 before the PCM turn the electric fan on.
Click to expand...

Thank you, forgot about the location of the switch. :doh:
 
My fan used to turn on at, iirc 190 ish. Stopped working, I jumped the harness side plug for the temp switch and it came right to life so I replaced the switch. Ran it up to around 215 the other day idling and it never came on. Maybe I have an air pocket.

Thanks.
 
ehall said:
91 doesn't have the radiator fan switch, the ECM controls the fan using a sensor in the thermostat housing and the A/C compressor clutch

I think the 91 FSM has the old RENIX text for the electric fan. Anybody got one for ~1995 that shows different information?
Click to expand...

FSM for 96 shows 218* to switch fan on, 209 to switch off.Sensor in T-stat housing that feeds ECU controls this. Temp sensor in back of head(96) feeds dash gauge-which always reads hotter.

Wayne
 
Wayne Sihler said:
FSM for 96 shows 218* to switch fan on, 209 to switch off.Sensor in T-stat housing that feeds ECU controls this. Temp sensor in back of head(96) feeds dash gauge-which always reads hotter.

Wayne
Click to expand...


I once put a manual temperature guage in the thermostat housing to verify the temps the ECU was seeing. The manual temperature guage and the in-dash guage was always within 3* +/- of each other. My assumptions is that either the wires from the T-stat housing may have a lot of resistance or the ECU itself maybe questionable in that area.

Then again, maybe the sender itself may not be too accurate. By-the-way, I have never tested it nor replaced it.
 
Anyone know what temp it kicks on for a 1997? The Haynes manual speaks nothing about it. It just says to check ohms when cold (7000) vs hot (1000)

I'd like to add a Taurus fan, and just have the high speed on a manual switch to simplify things.
 
Could be wrong (happens all the time) but on your late model I think the PCM controls the efan based on the CTS/gauge sending unit in the thermostat housing.

If you are going to wire in a switch, best isolate it with a diode to prevent feedback to the PCM.
 
I am going to have the PCM control the low speed while I control the High speed. I will use a relay to shut off the PCM's low speed when my high speed is engaged, along with a diode to keep the relay happy when the fan turns into a generator.
 
I was looking for someone who has used a scan tool to monitor the temp. According to my gauge, it comes on around 210 also, but we know how accurate gauges can be and when you are out wheeling or hauling a trailer, having the extra heat in the coolant could cause detonation. I know in LS based engines, after 220 degree, you have to really pull timing to keep from getting detonation. I just don't know on these 4.0's
 
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