A previous owner wired an aftermarket temp sensor to turn on the fan with the probe in the radiator. This was done because the fan was not turning on properly. I was going to hook everything up the way it is supposed to be, and here is whats up. Everything is good, so I figured that the fan temp switch was the issue. I know it is supposed to be on the pass head, but the knock sensor is there. And on the driver side is a bolt plugging that hole. Also, the switches that are sold for replacement will not fit these holes, they are too big, I compared the knock sensor threads to the temp switch.

Is my single fan controlled by the ecm? I thought it was not.

 

Yes
Primary by ECM ; Aux fan from mech switch in head
http://www.austinthirdgen.org/mkport...ine_wiring.gif

You sure, KS is mounted in bottom of block above oil pan rail; pass side

 

That is for the dual fan set up. I have the single fan. Thanks though.

 

Single fan TBI cars were controlled solely by the fan switch, which is supposed to be in the pass side head. The knock sensor is supposed to be in the pass side block (below the fan switch). They both have the same connector types on them.

But - FYI - something to consider ... I switched to a similar seperate fan controller as you currently have, with the radiator probe. I did this because no matter what brand fan switches I tried, I always ended up replacing them within 3 months - most wouldn't last 30 days - I even tried a $80 switch - and out of frustration I installed a seperate fan controller from Flex-a-lite, and I haven't had any cooling issues in 4 years now. It's totally adjustable, has provisions for manual on and off switches, and never fails. So, although it may not be original, the previous owner might have done this for the same reasons I did, because the factory setup just doesn't cut it.

 

Where did you install the probe? Mine is near the upper rad hose. I will be replacing the rad soon and wonder if there is a better mounting location.

 

Mine is installed at opposite location - there wasn't much wiring included for the probe, and that was the only location it would reach given that I installed the controller on the pass fenderwell.

 

Are there 2 sensors in your Thermostat Housing? I am pretty sure I pulled my housing from my 90 Formula TBI car and it had 2 Sensors in the housing, one of them could have been the temp sensor.

I have a Service Manual here and I will look tomorrow and see how the Fan wiring is set up and controlled on a TBI car. about to head out and watch Iron Man 2.