After doing the DeWitts Rad/Fan combo 3 or 4 weeks ago, I wasn't happy with the temps the fans were going on and off at...

They would come on at about 200 and off at 195 ! Supposed to come on at 195 and off at 170...

Called and ordered ($26) a new temp switch and this time I got the 185/170 switch....

Works like a champ and I'm much happier with my temp range now....

 

Glad you posted this. I thought mine were going on and off kind of high too.

Are your switches in the heads or do you have a bung in the rad?

 

I used the one switch for both fans - it came pre-installed in the radiator from DeWitts.

I was hoping they'd give me the new one free...but it was $26. I am convinced now the the one it came with was bad.....

 

Interesting. I have to say mine is working great. I got the 195/175 switch in mine. Thing is though, according to my laser temp gun, I do not seem to be getting any hotter than 180 degrees, even though the switch listed on the paper/instructions is suppose to kick on fans at 195. According to my stock temp gauge, it seems accurate. I am starting to question the laser temp gun. I measure it at the thermostat neck on the intake and upper and lower inlets on the radiator. I can watch the gauge inside the car quickly drop once the fans come on. My thermostat is a 180. So I would like to be as close to that all the time vs going to 195. Maybe I got a different switch than what the instructions state. MRJLR, was the original switch stamped with the temp code when you removed it?
Thx,

 

Good question ! I'll look at it when I get home in an hour and let ya know....didnt thint to look for any markings...

I'll tell ya this though.....the new switch is doing exactly what it's supposed to !

 

Did u ever get a chance to look closely at the old temp switch?

 

OK.....I checked it very carefuly.....no markings on it at all. No stamping...no lettering..nothing..kinda odd.

 

Actual activation temps with the Spal switch are higher because the switch is mounted in the radiator tank instead of the intake manifold. I ran into this as well. I had a Spal 185 on/165 off switch and it is mounted in the radiator....It was coming on at 195-197* and off at 175-180*..... I wasn't happy with that so I bought a Zirgo 180* on/ 175* off temp switch and mounted it in the radiator tank and it actually activates late also....it kicks on at 187* and off at 178*. This is better for me but still warmer then what I would like. My intake water cross over ports are already filled with temp sending unit/heat hose so.... I have no other options now unless I can find like a 170* on/160* off temp switch....that would get me a true 180* on and 170* off activation but...I have not found that kind of switch anywhere.

 

With my NEW 185/170 switch, it is working perfectly...

 

Alan, yep, I remember reading your thread about that switch. I thought somebody at Dewitt told me that the switches are marked. Otherwise how the heck do they know which is which. Radiator thermostats are stamped with the temp on them. As I mentioned above, I need to do some testing again with my laser Temp Gun. Is intake/thermostat neck the best place for the most accurate reading? With in how many degrees of accuracy should I expect?
Like I said, seems to be working, but the temp gun and the temp gauge conflict with each other. In other words, the temp gauge in the car seems to be in line with the dewitt temp switch, but I am more inclined to side with the temp gun even though its reporting a much lower temp reading.

 

Aim the temp gun on a dull section of the thermostat housing or water cross over on the intake....preferbly bare aluminum or black paint....nothing shiney....

My experience with 2 different infrared temp guns is, I can shoot the same spot 5 times and get 5 different temps....ESPECIALLY on headers....Not to mention you are shooting surface temp, not the water temp (unless you shoot it at the radiator coolant with the cap off which I have done but it will read slightly cooler there.) Usually the temp gun readings on the water cross over are relatively close to my temp gauge...not usually more then 10* apart...but I think thats just the difference in surface temp vs. water temp...

I basically just use a cheap mechanical full sweep gauge(like Auto gage or Equiis) with the temp sending unit in the intake cross over and stick with what it tells me. Ironically it matches my original in dash temp gauge with the sending unit in the head pretty damn close....Atleast at 180-190* they are within 5* of each other...

No way would I be running your 650hp big block at 195* consistantly.....not on todays fuel especially....

I really don't like seeing over 180* at all on mine and I never hammer it if its over 170*...... Mine normally stays under 180* while driving without the fan on unless I get behind some cars/trucks blocking my air flow or I am running in slow speed/bumper to bumper stuff....then it will creep up to 186-188* pretty quick, the fan kicks on and within a minute or less its down to 178* and the fan shuts off....In traffic situations the fan will just continue to cycle the temps up and down like this continuously...No biggie and as soon as its moving its back below 180*....

 

I will test it again this wknd with the temp gun. So basically the surface temp I assume is going to read possibly up to 10* cooler than what the actual water temp is?
Also is that zirgo temp switch, a direct fit into the dewitt radiator in the place of the temp switch they provide? Send me the link or let me know where you got this switch from.

 

http://www.zirgo.com/catalog/Tempera...Control-Switch

Mine is the fixed temp switch, 180* on. But with it in the Dewitt radiator tank it's actually kicking on at 186-188*. it does work consistently though. It was about 10* less then the Spal 185* on switch.

 

Has anyone tried an adjustable temperature control switch?

I have a bb in my 76 with Dewitts radiator and dual spal fans. Engine temps cycle between 205f and 195f. This is with Dewitts 185 temp switch. I would like it to run cooler.


roger

 

that switch in the pic. is a SPAL. the adjustable ones work well, suspect most are made by the same company no matter who you buy them from.

 

Guys, Spal offers two switches and both have a 20 differential.

195on/175off
185on/165off

These are cheap switches and the accuracy is probably +/- 5 degrees.

Everyone wants to run cooler, so they think they need the 185 switch but if you use a 180 stat, it won't let you get to 165 to shut off and the fans will run continuously. You could change to a 160 stat and that might work but they also have a +/- 5 deg variance. I like using the 195 because cycling between 200-180 is not a problem and it keeps the fans off and reduces power draw.

The un-marked switches were from a new company we tried and they are all 195/175 swtiches. They closed and we recently went back to Spal and they are all marked