Threw in a Hypertech Cooling Fan Switch today(200 on 185 off). Noticed 2 things.

First - The secondary fan comes on around 170 degrees and won't turn off until the car has cooled down for awhile. Stays on the whole time I'm driving and I'm running a 160 stat.

Second - The primary fan also comes on when the car is running but only when the secondary fan is on. Key on engine warm only the secondary fan runs.

Anyone have these same issues? I'm thinking that since the secondary fan is kicking on before the primary fan then once the car is running it kicks the primary fan on???

 

Maybe wrong switch ?
Test it with DVM in some boiling water

Has little bearing on operating temp ; is only the point when the stat opens.
Airflow through the radiator controls the temp

Because the ECM independently controls the Pri fan and your new fan switch controlling the Sec fan is turning it on at a lower temp
than the stock Pri fan temp programming
(Assumes all stock wiring / programming ? )

 

Thanks for the tips. Everything is stock wiring. I'm going to pull the Hypertech Switch tomorrow and throw in a Duralast SW505. The Duralast SW505 closes at 212 degrees so they say.

 

I also installed the same fan switch on my new engine. It's garbage. It turns on at 150 and does not shut off. I did a search on here and was surprised many people have the same problem with these. I just purchased a new fan switch from autozone (sw505). I'm going to install it today.

 

If the temp range suits , could always buy a quality unit .
I have never has a problem with these and the temp range is pretty much as advertised

http://www.racerpartswholesale.com/p...n_Accessories2
http://www.racerpartswholesale.com/p...n_Accessories2

NB;
Requires a cheap 1/2" - 3/8" NPT reducer if you have the large hole found on older heads

 

you have had good luck with these ??? im on my 2nd hypertec it turns on at about 120 & never turns off & needs to go in the garbage been looking around for options but never seen this befour thanks !!!!

 

Be certain that the temperature switch drives the fan RELAY and not the fan motor itself.

In addition to the other suggestions, the AutoMeter 3246 has worked well for me (203° on, 187° off).

 

Have used several over the years.
Currently have the 195F unit in my 383 race motor.
Going by the stock gauge, it turns on 197-8 ; turns off at 178

 

thanks im ordering one today. it is hooked to the relay when i say it never turns off. i ment that with it turning on at 120 instead of 185 it never gets low enuf to shut off when running. should shut off at about 175 but you have to let it set to cool under 120, or as soon as you hit the key you hear the fan turn on. & i would rather it not run all the time at 120 & up.

 

Autozone didn't have the SW505 in stock special order only. Went to Oreillys Auto and they had it but in a different part number, TFS4 (BWD Engine Managemnt Technology). Slap it in this morning and bingo!! The Temp Gauge only gets a tad past the middle mark when the fans kick on. Hook the scanner up and it says that it's closing at 219 and opening back up at 201. The part was $13.99. The hell with Hypertech, lol.

 

Well I installed my sw505 switch last night. Works as advertised. Add me to the "hell with hypertech" club. They wouldn't even answer my emails.