Help with engine compartment cooling fan

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sggoat

sggoat

10 Year 15 Year
Joined
Jan 22, 2007
Threads
66
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3,225
Location
Alva, Fl.
My '77 was originally equipped with a carb cooling fan, but it was removed, apparently with all the smog eq. I want to replace the fan system to help with fuel boiling in the current carb(Weber) and when I get the rebuilt Aisan installed.
No luck finding an orig. fan, but I found 2 bilge blowers from a Sea Ray boat that I think will work ok. Got one mounted in the driver's side space up front, but now need to figure out the wiring. The orig fan plug is still there-(proper wire color codes). The 75 carb I have has the rear temp sensor with it--but the original firewall plug connector that I think is for this has 2 pins--the carb sensor only has one---was there a change to this system from 75 to 77?(I think the fan was not an option until 77, but not sure). Is there a temp sensor("thermo-switch") that has two connectors on it?
There is also a separate relay shown on the FSM diagram that is listed as an "M3 relay" that connects to the fan relay under the psgr side firewall-looks to be the one that actually starts the cooling fan motor-can't find this relay at all.
Any help here would be greatly appreciated.
cooling fan relay.webp
cooling fan diag.webp
cooling fan wiring diag.webp
 
FJ40s started getting cooling fans in '76 in California. My '78 has a single-stud temp switch. I'll have to dig out the temp switch for my CA '76. Rather than hanging below the intake manifold (like the '78), I believe it was mounted on a 3" tall bracket on top of the intake manifold, just behind the carb. It had a plug and I'll have to look at it to see if it had two wires/connections. It may have had a ground wire. The control box you show in your post was located behind the heater duct in the passenger footwell and provided the relay function; there was no second relay. There was also an in-line fuse wrapped in the harness next to the control box.

By the way, there really should be no problem finding an original cooling fan. I see them for sale all the time. Keep your eyes open.

Edit: Just looked at the photos you posted again. The temp switch shown in the second photo is like the one that was on my CA '76. I see there that it didn't have a ground wire, but rather had a return wire to the control box. I don't know when the change from two-wire to one-wire took place; possibly with the '78 model year. My '78 is a Sept. '77 truck that I bought new. The third photo that you posted shows the temp switch circuit as used on a '78.

sggoat said:
My '77 was originally equipped with a carb cooling fan, but it was removed, apparently with all the smog eq. I want to replace the fan system to help with fuel boiling in the current carb(Weber) and when I get the rebuilt Aisan installed.
No luck finding an orig. fan, but I found 2 bilge blowers from a Sea Ray boat that I think will work ok. Got one mounted in the driver's side space up front, but now need to figure out the wiring. The orig fan plug is still there-(proper wire color codes). The 75 carb I have has the rear temp sensor with it--but the original firewall plug connector that I think is for this has 2 pins--the carb sensor only has one---was there a change to this system from 75 to 77?(I think the fan was not an option until 77, but not sure). Is there a temp sensor("thermo-switch") that has two connectors on it?
There is also a separate relay shown on the FSM diagram that is listed as an "M3 relay" that connects to the fan relay under the psgr side firewall-looks to be the one that actually starts the cooling fan motor-can't find this relay at all.
Any help here would be greatly appreciated.
Click to expand...
 
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Mine is a June 77 Ca. rig. , but as I said, the carb I'm putting back on it is a '75. The sensor is a single pin connector, and came with the carb. If there is a 2 pin thermo-switch connector you know about, please let me know. I'll have to get some pics up of the carb sensor, and the truck's pigtails. Thanks for the info.
Gary
 
The temp sensor at the carb goes into the emissions computer and has nothing to do with the carb fan. The carb fan sensor is separate.

The early carb fan was in the far front left corner of the engine compartment.

The fj40 fan looks like this, but this one is an fj55 fan with a custom mount. The fj55 version mounts to the radiator shroud. The fj40 version is supposed to mount to the fender side. I bought this at a swap meet without knowing and made it work. To be honest, the mounting works, but I haven't had time to get the relay and sensor sorted, so it doesn't really 'work'.

attachment.php



At some point before '78 it was moved to the left cowl, right across from the carb. This would be a good spot to mount the bilge fan if you use it. I would guess it will work ok. The original cowl fan moves a lot of air.

I believe this is a picture of the carb relay in my '76. Not 100% sure though.

attachment.php
 
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I have a stock 77 with the fan on it... Fan doesnot work ( not sure why?) but everything is there! Let me know if you need me to look for you?
 
After removing the heater duct, the cooling fan relay was located above the relays Fast Eddy showed. On mine, these are the seat belt warning and buzzer. I traced the wiring to the cooling fan from this relay, and found the 5 amp fuse(mounted right next to the relay assy) was blown-replaced. The wire to the carb "thermo switch" was in the same harness as the brake warning switches(hooked to the bottom of the dual master cylinder) I had the plug mis diagnosed as a plug up near the firewall(that had 2 spade connections on it)--more later--
 
Saw the fuse holder in your pic-that's what let me find it--thanks. Pics of the bilge blower install-sorry none of the wiring /plugs yet-will try to get them tomorrow
carb blower1.webp
carb blower2.webp
 
Found the wiring for the blower. Original assumption was partially correct-the 2 pin plug at the center of the firewall actually had the connection to the carb thermo sensor(green wire), plus the manifold temp sensor(lt blue wire) used in the earlier removed emissions computer. As far as I can tell, the manifold sensor didn't impact the carb cooling fan circuit, so I'm thinking I don't need to connect this one up.
Thanks for all the help with this one
Gary
 
sggoat I know this is an old post but I am looking into installing an after market carb cooling fan kind of like what you did, wanted to know about the fan you bought and how its working for you. I have been looking at a number of possibility's but nothing so far. Would love to find a stock fan but that's far and in between. Thanks
 
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