Electric fan conversion temp. question

[Insubordination]

I've been thinking on this for some time, but my limited knowledge has me stumped.

I'm converting to electrical fans. And I want them to start automaticly at a given temperature. My thermostat in my Olds 350 engine opens at 195 F (91C). A stock thermostat in accordance with the service manual.

So what I'm wondering about is at what temperature should my fans kick in / what temp unit to get?

I have one lying around for 200 F (93,3 C), but that seems a bit to soon.

Anyone?

[odaci0us]

I'm pretty sure they should shut off at 5 degrees after your thermostat opens.

[gmachinzz]

Remember too that the thermostat gradually open until at 195 then its fully open so you still have some circulation. I would go with a 212-202 temp switch so its rated just above your t-stat rating. This way, you get some circulation through the system at moderate and higher speeds where airflow should be sufficient enough to keep engine cool without the fan kicking on. If you have the fans come on too early, you never really give your cooling system a chance to shed heat first before a fan is even needed to kick on.

It's this reason why I think most people choose too early of a fan turn on. You want the off temp to be just slightly higher than the t stat open rating. Hope that clears some questions up.

[Anubis]

Where is a good place to get temperature sending units? I'm a cheap bastage and don't want to pay Summit $35-$40 for one. Anyone know of a good source?

[Insubordination]

Where is a good place to get temperature sending units? I'm a cheap bastage and don't want to pay Summit $35-$40 for one. Anyone know of a good source?

I second the cheap bastage stance for myself as well. And good question.

[DRIVEN]

My research indicates that an OE Grand National fan switch (3053190) is on at 210* and off at 200*. These were the crossover numbers according to the interwebz. Hope it helps:
AC Delco 15-4229
B/W TFS1
STD TS-147
Niehoff DR137S
Echlin FS110

[84cutspreme]

I just installed new dual electric fans, the company I used recommended using a 160 T-stat. Fan sending unit turns fans on @ 195 and off @ 175. They say that 160 will run cool enough so fans are not running all the time

[80ELCAMINOFLAKE]

I just installed new dual electric fans, the company I used recommended using a 160 T-stat. Fan sending unit turns fans on @ 195 and off @ 175. They say that 160 will run cool enough so fans are not running all the time

Im thinking of running a 160 t stat in my water neck as well, have u test drove it to see if it stats freash?

[gmachinzz]

I would not suggest running a 160 t-stat....you will get a much better and more complete fuel atomization if you run between 190-200. If you run too cool you'll use way more fuel and it'll build up a lot more carbon deposits. Running an engine too cool is not a good thing.

[bill]

From what I have learned and have been told, Olds motors like to run at 195-210 degrees, depending on the season. Any t-stat that opens at 160 or even 180, would keep the engine too cool and not at optimum performance temp. After my lastest fiasco with my electric fan, I see no benefit to pulling off the manual fan and hope and pray the electric fan/relay doesnt burn up! If you do go with an electric fan, dont use a 30 amp relay...use at least a 40 amp one. I believe that is why mine burned up. good luck!

[80ELCAMINOFLAKE]

I would not suggest running a 160 t-stat....you will get a much better and more complete fuel atomization if you run between 190-200. If you run too cool you'll use way more fuel and it'll build up a lot more carbon deposits. Running an engine too cool is not a good thing.

Oh i see, ok i think i will get a 180, they all the same price at autozone 11.99 lol

[FE3X CLONE]

Running a 160 or 180 is not going to hurt your engine. At least not any appreciable amount. I ran them for years in both daily driver's and my performance cars.

Yes, a hotter thermostat will help aid in fuel atomization but it is also detrimental to power. You do have a trade off here. If you want more power you need a cooler/denser fuel/air. If you want better fuel economy, you need better atomization.

[bill]

Running a 160 or 180 is not going to hurt your engine. At least not any appreciable amount. I ran them for years in both daily driver's and my performance cars.

Yes, a hotter thermostat will help aid in fuel atomization but it is also detrimental to power. You do have a trade off here. If you want more power you need a cooler/denser fuel/air. If you want better fuel economy, you need better atomization.

I think in racing applications, this would be correct..... but for most street applications, it makes better sense to increase fuel atomization....I think the power gain from cooler/denser f/a mixture will not make up for the loss in economy...just my opinion

[Insubordination]

Thanks for all the informative posts. I love a constructive debate.

My engine is stock except for the intake manifold. So I will use the thermostat that is specified for the engine (195 F). I don't have much power to speak of, and don't need worse fuel economy with Norwegian gas prices .

Think I will take Gmachinzz' advise and get a 212-202 temp switch. His input was in accordance with my own reasoning, so thats my best bet.

[Anubis]

My research indicates that an OE Grand National fan switch (3053190) is on at 210* and off at 200*. These were the crossover numbers according to the interwebz. Hope it helps:
AC Delco 15-4229
B/W TFS1
STD TS-147
Niehoff DR137S
Echlin FS110

Thanks for your homework driven. I found similar info but not all part numbers I found referenced were correct. Some of the part numbers are for a newer style sending unit with 2 terminals and variable impedance. The correct part will have (1) terminal and go high or low depending on condition. The GM PN 3053190 is correct and Auto Zone sells a Santech replacement for it for $10. You can also find them in the salvage yard across several 88' - 92' GM vehicle platforms. I need to go to the yard today for some other stuff so I'll me looking. Hopefully I'll find something because I need the unique plug required.