Temperature switch ideas?

[Glen]

Compressor Works/Cooling Fan Control Part Number:733653 Adjustable Temperature Range: 32°F - 258°F Probe Type: Push-in
Auto Zone $17.99

[GM_Guy]

Summit/Jegs is where you will need to look for that, its not a factory part.
ie: flexalite Part# 31147 Note: YOU MUST USE A RELAY to turn your fan on/off even with this thing or you will burn it up.

Just consider a temp sensor in the water jacket is going to be a lot more accurate than an external probe. I know people who have hose clamped them to the rad hose rather than the radiator fins to get the things to work a bit better.

Alex.

[Glen]

Sorry, they are all to be used with a relay. No it is not a factory part , as the ele. fan is not a factory part.

[1987cp]

Compressor Works/Cooling Fan Control Part Number:733653 Adjustable Temperature Range: 32°F - 258°F Probe Type: Push-in
Auto Zone $17.99

Thanks for that info!

For a cheap probe kit that's sort of a cop-out anyway, I like the idea $18 locally over $40-plus shipped from Summit. I figure by the time I get near $40, I should probably be considering some of the nicer options.

Were there any concerns about mounting the little box with the potentiometer somewhere out of the way? It looks like the probe has a long enough tube/lead on it to mount the box pretty much wherever ....







GM_Guy: So you disagree with the folks who say the radiator probe is somewhat better since it can give a more accurate idea of whether the radiator is doing its job adequately without additional airflow?

[Glen]

No, I just screwed it to the inter fender. I put the probe as close to the top hose as I could. The pic. is before I cleaned up the wiring. I have a temp gauge so I know the temp of the engine. The sender is adj. so it will come on when I want it to. As I said before it works for me.

[1987cp]

Well, I've got it! Looks like there might be enough capillary to mount it all the way up next to where my new fuse box is going to go, requiring only a very short control wire. Slowly getting the control circuits buttoned up ....

The instructions and the AZ guy both were pretty specific that the probe is to be stuck inside the radiator hose, but shoving it through the radiator fins makes more sense to me, so long as it can be held in place adequately.

[Steve'87]

You may not have A/C, but one thing you could do is wire the high side to the thermal switch, and wire the low side to run whenever the A/C was running.

[1987cp]

Why that way and not low to thermal and high to A/C (which is what I've been planning to do)?

[Steve'87]

Personally, I would want the maximum cooling power associated with the thermal switch. I would not want the high speed fan to run unless it was needed. Electrical draw and noise concerns. And that's the way I've seen them work on cars, low speed or first fan comes on with A/C, then if not sufficient to cool the engine, the thermal kicks in and the high speed or second fan comes on for more cooling power.

[Glen]

Stick it in the radiator, it will stay there. I have never seen it inside the hose.

[1987cp]

Interesting. On this particular radiator (copper-brass 2-core) it seems a bit loose (more so than on the aluminum 1-cores that I consider more typical), but I'll give it a go and report back.

It did perform well in a driveway test today. Ran the engine up to temperature, thermostat opened at 180 degrees, and shortly afterward I noticed the fan had kicked on. Needle stayed right at 180 during the test, and the fan ran on for probably 3 or 4 minutes after I shut the car off. So far so good!

Only real problem with my current scheme, wiring the high speed to the A/C doesn't work so good when refrigerant is low and the compressor is cycling on and off. Maybe I'll run a manual switch on the downstream side of a diode and call it good for now.

[GM_Guy]

Get a piece of exhaust tubing the same diameter as the upper rad hose. Weld a bung in it to thread in a temperature sensor. Cut rad hose, insert new tube. Done.

Alex.

[1987cp]

Um .... why?

[1987cp]

Well, I took the car for a spin with the new fan and the $18 AutoZone thermal switch. Seems to cool pretty well just on low speed, at least in the cooler weather we're having. I know demands will be different in very hot weather with the A/C going too. (going to spend a little time today inspecting for A/C leaks so it can quit just sitting and cycling endlessly on and off)

I was puzzling at the temperature probe again, and then suddenly realized that if I tuck the capillary behind one of the tabs on the fan in such a way that it's retained but not crushed, I probably don't have to worry at all about the probe falling out.

After I got home, I noticed the fan cycling on and off as the car sat in the driveway, so I turned the adjustment knob slightly to the right to help it make up its mind. Nice that this switch is so easy to tweak.



BTW, it's my intention later on to install a nice variable-speed fan controller from a company called DCC, thus the desire to spend as little $$ as possible on this stage of the fan installation. I know little about the company personally, but some guys on another board whom I'm pretty confident that they know what they're talking about say the DCC units are worth the $30ish premium over a Flex-A-Lite, and of course it goes without saying that it'd be most ideal to have the fan running only as fast as necessary and to eliminate the slight extra strain of cycling on or off immediately. According to this article, the DCC controller is capable of not only switching the fan on at 50% power when the A/C is turned on, but capable of running at some much lower speed as well when only very little cooling is needed - which means that in the case of my driveway shutdown routine today, instead of cycling on and off a couple of times, the DCC would have instead just ramped the fan speed down slowly until it was satisfied the radiator was cool enough to shut off the fan completely.



Anyway, thanks a lot for the pointers I've received, and with luck this thread will be of use to other people pondering what to do with their fresh electric fan installs.