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| Hot Wired Radator Fan (Page 1/2) |
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MasterBaker
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AUG 22, 12:11 PM
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You all are going to see a lot of posts from me over the next few months. Just purchased a 1986 Fiero GT with 2.8L. The guy I purchased the car from had issues with radiator fan to turn on or overheating. The radiator fan has been hotwired to run constantly. I would like to return the operation of the fan to factory spec. When I look at the fuse box (interior) there is a green wire that runs from the front of the car to a green fuse in the box. I’ve never seen a wire run external to a fuse box. Would it be hotwired from the fan direct to fuse box? How would a mechanic typically wire a radiator fan to run constantly? Trying to figure out someone else’s rigging is not fun.
If the fan was not turning on, is the issue likely a faulty temp sensor for the fan. Little more history, the car has the original AC setup and is low on R12, no cold air. Could that trigger the fan not to operate? I know the fan is set up to turn on when AC is turned on. Didn’t know if that could play into the issue. As always, thanks!
My next post will be on converting R-12 to R-134
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olejoedad
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AUG 22, 01:15 PM
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The fannis controlled by the FAN switch on the engine (or the HVAC control on any A/C setting) providing a ground to the FAN relay, located on the front bulkhead ahead of the driver side headlight.
The easiest way to trigger the FAN would be to provide a ground to the relay coil.
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Vintage-Nut
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AUG 22, 01:19 PM
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| quote | MasterBaker
The radiator fan has been hotwired to run constantly. |
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Fact or Theory?
A/C equipped vehicles have a separate signal wiring to the ECM for a fan control [edit: for L4 engines When the A/C control switch is on, the ECM gets the A/C "On" voltage on pin 21 and closes the ECM coolant fan relay control to ground. The A/C clutch does not have to be engaged for the ECM to turn the ON the fan.]
Edit: On V6, the A/C Pressure Switch closes to run the radiator fan.
IF an A/C Pressure Switch Fails (Grounded) then the radiator fan can be "On" constantly.
Without Any 'History' on the Car:
My suggestion is to disconnect the A/C Pressure Switches from the A/C Compressor, then run the engine....
If the radiator fan stops, then maybe you found the source.
Edit: Ask me why I know....[This message has been edited by Vintage-Nut (edited 08-23-2023).]
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Patrick
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AUG 22, 05:04 PM
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| quote | Originally posted by Vintage-Nut:
Fact or Theory?
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Just to possibly elaborate on the points you brought up... I removed all A/C components from my Formula (I used the car for autocross and didn't want the added weight of something I didn't use), but I retained the A/C dash controls. I still have full manual control of the rad fan using the A/C controls, and the fan switch (Dickman 210° on and 200° off) works normally as well.[This message has been edited by Patrick (edited 08-22-2023).]
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Vintage-Nut
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AUG 22, 08:47 PM
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Precisely the Point:
IF the A/C control is 'Off' AND the A/C Pressure Switches from the A/C Compressor are disconnected, AND the radiator fan stops; then maybe MasterBaker found the source.
IF not, then I believe the fan has been 'hotwired' to run constantly....
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Patrick
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AUG 22, 09:03 PM
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| quote | Originally posted by Vintage-Nut:
...the fan has been 'hotwired' to run constantly....
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Probably by grounding it up front, as was suggested previously. I suspect the "green wire" mentioned by the OP has nothing to do with the rad fan.[This message has been edited by Patrick (edited 08-22-2023).]
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theogre
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AUG 22, 09:13 PM
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| quote | Originally posted by Vintage-Nut:
Fact or Theory?
A/C equipped vehicles have a separate signal wiring to the ECM for a fan control. |
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Not. Most Fiero ECMs don't care or know about fans.
ECM have 2 pins for AC
1. Input. All switches closed telling ECM you turn On AC & limit switches are happy.
2. Output. Final Say that AC Clutch to turn On. Because ECM will Not turn the AC under rules in it's programing. Like Will Turn Off AC when you "floor the gas pedal."
Some cars have AC Limit Switches wired to Rad Fan control.
All 87-88 Fiero Duke ECM control the rad fan all the time not just for AC, Even has support for 2 speed rad fan but unused ECM pin for Fiero & most others.
Either way Fiero AC/heat head bypass that when AC is On and force On the Rad Fad and V6 blower (for cars w/ them). So make sure head has Off Button is Push Down. (That's the only way to Turn Off the Heater Blower too.)
If fan is still On...
1. is pull E-fan Fuse to see if control wire & fan relay actually work and fan(s) turns off.
If true... then need to find out where green wire is grounded.
If false... Fan relay can be bad or Fan is wired to bypass the relay. But note that Bad Relay often want to stay On even w/ I-key is Off because Big Main power wire runs directly to the battery via Fusible Link A------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)
The Ogre's Fiero Cave
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MasterBaker
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AUG 22, 10:00 PM
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Thank you all so much! I follow everyone’s suggestions. Fan turns on as soon as ignition switch is turned one notch forward. Next I took an closer look at radiator fan wires. I noticed a black wire running out of snakeskin with a wire splice. Some mechanic cut the black red wire and ran a black wire thru the front wall at steering wheel straight to outside the fuse box. He used a metal clip and wired it where the fuse plugs into the fuse box. 😡 Not impressed at all. The former owner told me car didn’t not overheat but was worried fan did run much and temp were up over 200 degrees. He told the mechanic the sensor may be bad. Mechanic totally rigged it.
Question on the AC switch that turns on radiator fan. If the system is low on Freon will that disable the switch when you turn on AC inside car. Car does not blow cold air at all. It’s very low on Freon. Didn’t know if that switch also relies on gas pressure inside AC system to trigger fan.
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Patrick
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AUG 22, 11:11 PM
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| quote | Originally posted by MasterBaker:
If the system is low on Freon will that disable the switch when you turn on AC inside car.
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Did you not read my post?
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MasterBaker
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AUG 23, 08:11 AM
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Patrick my bad. I apologize! I did over look you post last nite. Thank you so much for helping my understand how the cooling system functions with fan operation. Can’t thank everyone enough for your input!
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