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Radiator thermostats

larrywlarrywMember
Last fall, towards the end of the New England driving season, I was noticing that the car seemed to be running around 160. During the hotter weather it always seemed to run around 180-190. That 160 seemed a bit cool to me, so over the winter I decided to check my thermostat. I was wondering if there was even one in there. What I found installed was a Windsor style 160 thermostat.

I got a Robertshaw 180 installed, refinished my rusty cooling pipes and put in a full set of new hoses. I installed the revised fan relay set up along with supplemental grounds for the Kysor brand fan motors. I also figured out why the previous owner said the manually switched sucker third fan never seemed to help much. It was wired backwards and it pushed back against the first fan. They all spin like turbines now. Noticeably faster than with the diodes in there before.

I first filled it up with plain water to test it and check for leaks. After it warmed up only one fan came on. It ran that way long enough for me to seriously wonder if I'd mucked something up. Just as I'm pulling out the meter to start doing some checking, the second fan came on, ran for a few minutes, then shut off. After a little longer it settled into a regular cycle, which tells me that one fan is almost all it needs. If I run the manually switched third fan the second fan just doesn't come on. All the while my temp needle is right on the "0" of 180. I'm pretty happy with all this.

Now that I'm back on the road I'm noticing that the first fan evidently comes on while I'm moving because it's running when I come to a stop whereas it used to take a few moments at a stop before it called for fan. I guess the fan probably isn't drawing much current if the car is moving since the fan blades are being driven by the wind but do they like running constantly?

I'm wondering if my radiator fan thermostats are too low, ie; calling for fan before it's really needed. I've got a brass six (?) core two pass radiator with threaded in thermostats. I'm going to check to see what they're rated at, but what should they be? Are there different values available?
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George PGeorge PAdmin.
Larry,

I'm not familiar with how your cooling system is plumbed as far as which tank is the inlet tank and which tank is the outlet tank. I'm going to assume it is plumbed the way the OEM tank was plumbed.

Hot coolant from the motor enters the "lower" tank. The high temp thermal switch is installed in the lower tank. The oem switch was set at 85 degrees C (185 degrees F). The hex shaped replacement switch sold by the vendors is set at 77 degrees C (170 degrees F).

Cooled coolant exits the upper tank. The low temp thermal switch is installed in the upper tank. The oem switch was set at 70 degrees C (158 degrees F). The hex shaped replacement switch sold by the vendors is set at 60 degrees C (140 degrees F).

Most owners report with a 180 degree thermostat installed in the motor, that once the motor stabilizes at operating temperature, both fans will run continuously.

If you want to find a switch with an alternative setting, perhaps one of the vendors will reveal where they purchase the hex shaped replacement switches at, or perhaps you can browse the internet and locate a source. My guess would be it is a generic part available in many settings.

Spal sells a couple of switches, rated higher than 170 degrees (185 & 195 degrees F), but the threads are 3/8" NPT. Spal also sells an electronic fan control that is adjustable, the sensor for the controller also has 3/8" NPT threads.

Here's a link to Jeg's page for cooling system accessories: Jeg's Electric Fan Wiring Kits & Senders

This is interesting: Adjustable Temperature Switch

cowboy from hell
Last edited by George P
larrywlarrywMember
With some difficulty I got this information off the thermal switches in my radiator tanks and also confirmed they are plumbed as stock, hot coolant entering the lower tank.

First, the thermal switches are both the same, top and bottom tanks. They've got brass hex bodies, 1-1/8" across the flats, (a 1-1/8" wrench is almost a perfect fit) with a light grey insulating material supporting the spade terminals. They're marked "BEHR" and "Made in Germany" on the grey stuff. On alternate flats around the hex it's marked: 124 22, 10/7, and 85 77. The 85 and the 77 have the "degree" symbol (but my keyboard doesn't).

I googled Behr. I couldn't easily find their catalog and operating specs, but they do indeed make this sort of stuff. I'll look some more.

I suspect mine may have come from Precision Proformance. I say this because I know one of the prior owners used to have work done there. While scanning their website once I noticed they listed a thermal switch the didn't require relays. That's how I found the car to be set up before last winters work.

I'm going to give PP a call a little later but meanwhile, I'm trying to figure what the 85 77 means. On at 85 off at 77? On and off somewhere in that range? Any ideas? I'm going to try and read the inlet and outlet temps with my little IR heat gun as she warms up next time before we go out

One last thing, you said that most cars will have both fans running continuously when they are fully warmed up. That's even when they're moving? So obviously the fan motors are rated for continous operation. I guess I'm just lucky to find that only one is running.

So if this is normal, maybe further work on this issue will be postponed until the snow flies next fall.

I'd rather not fool with anything right now, it's time to put on some miles.
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