OEM Carb Fan Controller Replacement

[tls3601]

I hunted down all the old original stuff about a year ago and.........................it worked and still does!!!! I will say that my fan has never run for more than like seven minutes though. Some say theirs can run up to twenty minutes after turning engine off???? Anyways that is how my '78 rolls............Excellent contribution!!!

 

[unixman]

As I recall it's open, open and closed at those temps. Like I said above, "more like a switch".

Don't mean to sound dim but when you say the sensor is open, you mean there is no voltage/current present? Literally an open circuit? And there is no transition before it closes? Simply on or off? I'm not familiar with that sensor.

 

[Pin_Head]

It sounds like a thermal switch, like a Klixon or equivalent. They are either open or closed depending on the temperature. There is variable hysteresis, so you can choose a narrow or wide range of operation.

 

[unixman]

Must be. Didn't realize they weren't all thermistors.

 

[Pin_Head]

The logic isn't all that different.

If ign off and thermal switch on then:
Run fan until:
Thermal switch off or 20 minutes.

 

[x463]

I posted yesterday in the 16 page fan post - I have a parasitic drain on my battery traced to the controller. Otherwise it seems to work. I've did some investigation with the multi-meter and wiring diagrams and figured a few things out. There seems to be more understanding of the schematics of this gizmo here.

The wires -
Green/White - always 12+ w/ the inline 5 amp fuse
Black/Yellow - 12+ with ignition on (goes to emissions computer on driver side)
Light Blue/Red - goes to fan
White/Black - ground
Light Blue - goes to thermo sensor and is roughly 9.5 volts ALWAYS (the wiring diagram indicates wire should have black stripe - it doesnt)

If I ground out the Light Blue wire with ignition OFF - fan turns on.
If I ground out the Light Blue wire with ignition ON - the fan does NOT turn on
(This all sounds good.)

Here's my long winded question(s)....

Should the thermo sensor always be getting power? It does with the ignition on or off and I even left it over night thinking it might stop getting power after 20 minutes. I'm wondering if this is my drain.

I also hear a click when plugging the controller in - with ignition off. Normal?

Thanks -

 

[Weber Sarge]

I would think part of the timer relay would shut off power to the thermal sensor after a given amount of and time , and re-start the cycle once the ignition is turned back on to the run position . I'd bet with my limited electronics ability the timer itself is the root problem - and someone should be able to build a more modern IC-based controller and relays .
Sarge

 

[Solace in Solitude]

I would think part of the timer relay would shut off power to the thermal sensor after a given amount of and time , and re-start the cycle once the ignition is turned back on to the run position . I'd bet with my limited electronics ability the timer itself is the root problem - and someone should be able to build a more modern IC-based controller and relays .
Sarge

@unixman was working on a prototype back in August... You might reach out to him. OEM Carb Fan Controller Replacement

 

[x463]

I would think part of the timer relay would shut off power to the thermal sensor after a given amount of and time , and re-start the cycle once the ignition is turned back on to the run position .

I was thinking the same thing....but that doesn't mean I'm right. Looking for a better understanding of the circuits.

I'd bet with my limited electronics ability the timer itself is the root problem - and someone should be able to build a more modern IC-based controller and relays .
Sarge

Both @unixman and @GA Architect have built modern replacements...and there are other timer options. I'm going to attempt to fix mine first as it seems to be almost there...except for the drain. Might just be a minor fix with a $.02 diode/resistor/capacitor. I also have 4 spare/parts fan controllers that I could potentially scavenge for parts.

 

[x463]

@unixman was working on a prototype back in August... You might reach out to him. OEM Carb Fan Controller Replacement

That's the post we are in!

 

[Solace in Solitude]

That's the post we are in!

You've come full circle!! Sorry!!

 

[Pin_Head]

The OEM controller is a black box and I am not aware of a schematic diagram for it, so nobody knows the details about how it works. It has a relay, so it is not surprising that it clicks and a drain may be normal. A competent EE could discern the schematic diagram and reverse engineer it by looking at the PCB, but it appears that unixman devised a de-novo solution to the timer.

What this means is that you are on your own and in the dark. I wouldn't assume that a minor drain is abnormal as long as the timer works fine.

 

[unixman]

Light Blue - goes to thermo sensor and is roughly 9.5 volts ALWAYS (the wiring diagram indicates wire should have black stripe - it doesnt)
...

Should the thermo sensor always be getting power? It does with the ignition on or off and I even left it over night thinking it might stop getting power after 20 minutes. I'm wondering if this is my drain.

I also hear a click when plugging the controller in - with ignition off. Normal?

Thanks -

I don’t remember measuring if there was voltage present when the engine was cool, but 9.5V could equate to tens of milliamps depending on the resistive value of the thermistor. Does the fan switch on when you turn off the ignition and the engine is hot (>100C) and conversely not switch on when you turn off the ignition and the engine is cool?

Hearing a click when you plug in the controller would imply the relay is closing because the ignition is off and the thermistor value is within the valid operating range. That would also explain the relatively higher voltage (lower resistance) to the thermistor. However, I would then expect the fan to run every time the engine is shut off regardless of temperature.

 

[unixman]

The OEM controller is a black box and I am not aware of a schematic diagram for it, so nobody knows the details about how it works. It has a relay, so it is not surprising that it clicks and a drain may be normal. A competent EE could discern the schematic diagram and reverse engineer it by looking at the PCB, but it appears that unixman devised a de-novo solution to the timer.

The OEM controller is indeed a unique, single-layer PCB with a clever arrangement of analog components. I thought about closely copying the design, but the number of components and size of the PCB would cost more and be less reliable than a digital equivalent on a smaller two-layer board.

 

[x463]

I don’t remember measuring if there was voltage present when the engine was cool, but 9.5V could equate to tens of milliamps depending on the resistive value of the thermistor. Does the fan switch on when you turn off the ignition and the engine is hot (>100C) and conversely not switch on when you turn off the ignition and the engine is cool?

I haven't been able to check engine hot yet....too damn cold in Chicago. Just got the truck in December and most of the time it was unplugged b/c of the drain. Just started troubleshooting. It does NOT switch on when cold and when I ground out the post for the sensor the fan comes on and then shuts off when the ignition is on.

Hearing a click when you plug in the controller would imply the relay is closing because the ignition is off and the thermistor value is within the valid operating range. That would also explain the relatively higher voltage (lower resistance) to the thermistor. However, I would then expect the fan to run every time the engine is shut off regardless of temperature.

The click seemed backwards to me also...but the fan isn't running. So your original one doesn't click when plugged in?

I have 4 spares....the PO went through great effort to get it working and thought #5 did work. As a separate issue he mentioned a parasitic drain which he believed it was the radio. The mechanic that did the PPI (knows FJ40s very well) said the drain was the fan controller and unplugged it. Battery has been fine ever since. I'm going to leave it plugged in to try and judge the drain myself.

Looking at my box of fan controllers....

• one obviously has the two fried diodes
• one that somebody tried to fix some fried pathways by soldering a wire from A to B
• one that has a fried pathway w/o any type of repair
• one that doesn't show anything obvious

I can mess around with these and see if they click....but with the damage some have it might not be a validation of anything. I might also try swapping the pair of diodes into #1 as others have mentioned this as a common failure.

 

[Pin_Head]

With that many controller boxes and plugs, you should get together with unixman and bang out some replacements. That is enough that you could send a new one out and wait to get the core back.

 

[x463]

I was able to compare all 5 of my fan controllers. 3 won't trigger the fan when grounding out the sensor post. From my list above that would be the first 3 bullets. One of those 3 has 9 volts to the sensor with the ignition on vs. off. One gets 1/2 volt with the ignition on and 9 when off - this is the one with the pair of fried diodes. The other reads nothing regardless if on/off.

Here's were it gets a little interesting...the 4th one behaves exactly like the one in the truck EXCEPT there is no click when plugged in. In theory this sounds better but I wonder why it was in the spare pile? I can't notice anything physically wrong with either (with my untrained eye).

I'm going to attempt replacing the diodes in the 1st one and see how it behaves since I don't notice anything obviously wrong with it otherwise. - EDIT: Tried replacing the two diodes. That corner of the board is so fried it started crumbling. Didn't waste any more time on it.

 

[LAMBCRUSHER]

how did I miss this thread? Great tech Unixman

 

[Coolerman]

Here are the OEM part numbers I found when researching this:

Carb Fan Controller Part # 85927-60010 fits 1/76 - 9/77
Carb Fan Controller Part # 85927-60020 fits 9/77 - 1/79
Carb Fan Controller Part # 85927-60030 fits 1/79 - 8/80
Carb Fan Controller Part # 85927-60040 fits 8/80 - 91

Manifold Thermo Sensor Part # 89423-60010 9/73 - 8/77
Manifold Thermo Sensor Part # 89423-60020 9/77 - 8/92

Manifold Thermo Sensor Part # 89428-60030 1/77 - 12/78 This looks more like a water temps sensor

 

[x463]

Thanks for the part #s @Coolerman

I have 4 cases and 5 boards that physically look to be the same - all 4 cases have the Toyota part # 85927-60020 and Denso part # 078100-0062. They also say "Toyota 2F '78".

Curious on the manifold sensor part #s - overlapping ranges. I suspect any will work judging by the overlap but I still need to verify the sensor (my truck is a December of 1978 build).

For now - I've re-assembled two fan controllers using the best cases. The one that was in the truck unplugged when I bought it - that supposedly has a parasitic drain but seems to function. This is the one that clicks when I plug it in. The second one was in the spare pile and seems to function - but no click. I'm going to run this one for now. Realistically - with Chicago temps I may not know for a while if it works but at least I can verify any battery drain.