Carb Cooling (1 Viewer)

[dfmorse]

Does anyone know if there is documentation covering the carb cooling fan and the RELAY#1 & RELAY#2 circuits? I have checked my manuals:
36104E
36262E
98154
98126
Maintenance Procedures 98231 (1980)
Owners Man. 9763A
Haynes 313

and can't find a hint of info. The sensor is still available for $140. The circuits are mfg-disc.

 

[Coolerman]

The Haynes manual is the only place I have seen that has any information on this. The schematic they have for the 79 (available on my schematic page) shows the pin out of the M3 relay that controls power to the fan and has the pin out of the M2 relay/timer unit but no one has the actual schematic of the timer /relay circuit.

If someone would send me a defective timer module they were going to throw away I could draw up a schematic of that circuit if it's not epoxy potted.

 

[dfmorse]

Thanks Coolerman;
I just ordered relay#1 & rly#2 from SOR. We will see what turns up. Maybe I'll sent u one of these units for reverse engineering, that's what I bought them for. Some of these parts are listed new from Toyota, but are really not available. The sensor is available and I bought one of those ($140).


...

 

[Coolerman]

I can tell you that relay #2 is just a standard relay while relay #1 is the timer/relay. Pin #7 on relay one is the key to how it all works. When the sensor detects the temp it's designed for, that signals the timer module to GROUND pin #7. Grounding Pin #7 causes Relay #2 to turn on, closing its contacts and allowing current to flow to the fan motor. (In the 78 and earlier version there was no Relay#2, the timer module actually switched +12V to the fan motor directly) I do not know if the module is a simple timer or if it continues to monitor the temp sensor in a loop back mode to determine when to shut down. I have heard that is seems to be about 15-20 minutes then it shuts off.

Again if someone has a old fan module and temp sensor they would like to send me I'll pay shipping to get it here. I would also like to know exactly what the temp sensor is. It could be a thermocouple or a simple temp switch. Either could be gotten cheaper if the parameters for it were known.

 

[Fast Eddy]

I do not know if the module is a simple timer or if it continues to monitor the temp sensor in a loop back mode to determine when to shut down. I have heard that is seems to be about 15-20 minutes then it shuts off.

I really get the impression that it's not a loop-back. It always seems to run for the same amount of time. 20 min sounds right.

Feedback would be tough. The sensor would cool off sooner than the manifolds, so it would shut down pretty quickly.

 

[Coolerman]

I believe you are correct. The schematic even shows it as a "resistor" symbol implying it is in fact a resistive element similar to the temp gauge sensor. If that is the case then a simple ohm meter reading should easily determine the range of the sensor allowing a replacement that doesn't cost $140 to be found!