Radiator Fan works when AC is turned on...

Fan works when the wire to the switch in the passenger cylinder head is grounded (my first test)...

I just replaced the switch in the passenger cylinder head with an AC Delco stock switch, and the fan still will not turn on...let the car idle to 240 or so degrees (not quite to overheat, but close)...fan never turned on...

thoughts?

Could the brand new AC Delco switch just be bad, or could there be something else here?

 

doing some further research, the AC Delco part I installed (D1852B) may not be right for my RS...

Found a couple of sources that have said the sending unit in the Z28 and the RS 305 were different?!?

How does that make sense? Thoughts anyone?

 

With the key in RUN; Ground the wire leading away from the Coolant temp switch. If the fan works than the switch is suspect, if the fan doesn't work then something else is the problem ( relay, wiring, ect )

 

Yes...fan works when the lead is grounded--that was my first test, and noted above...

I did replace the switch with the AC Delco D1852B...some conflicting info out there about whether or not it would work with the RS, or is it a Z28 part only...either way does not make much sense to me that it would not..

Guess I'll try another switch--any recommendations out there for a switch that come son a bit earlier than the stock 220?

 

Just a thought my factory temp gauge is off so when I had a factory 235F switch installed it would not turn on until the factory gauge read 260. An IR temp gun and aftermarket gauge read 235. Same with my new switch at 210. Everything tells me the engine is at 210 when the fan kicks on except the factory gauge at 230. I believe SW502 is factory

SW500 1 3/8 x 18 Open Makes 230f ± 8
SW501 1 3/8 x 18 Open Makes 222-239 f
SW502 1 3/8 x 18 Open Makes 238f ± 8
SW505 1 3/8 x 18 Open Makes 221f ± 8
SW555 1 3/8 x 18 Open Makes 210f Breaks 205f

 

Sorry dude - I don't know how I missed that !!

Midas makes a real good point; Temp gauges are know to be inaccurate and it's very possible that your not as close to overheating as the guage is showing you.

The first thing I would do is this: (Leave everything intact as it is right now.)

Check the coolant mix to ensure proper mix of coolant and water and that the coolant is @ the proper level with no air trapped in the system.

VERY IMPORTANT: Check the radiator cap is rated for 15 pounds and that it has a good seal on the underside of the cap.

Start and run the car @ idle as you watch the coolant temp gauge and coolant overflow bottle simultaneously while waiting for the fan to kick on.

( STOCK fan switch should activate around 235-238 degrees )
( 50/50 mix with 15 pound cap will boil @ 260-265 degrees )

You should (obviously !) see the fan kick on BEFORE the coolant begins to bubble/boil back into the overflow. Running a car @ idle till the coolant bubbles into the overflow bottle will not harm anything. If coolant bubbles back into the bottle just shut the car down because there IS a problem with the switch. Could be a bad switch, could be the switch is not grounded properly to the block.

If the fan kicks on before the coolant begins to bubble,... take a reading from the temp gauge and then subtract that from 238; ( or subtract 238 from the temp gauge reading). This is approximately the amount your temp gauge reading is 'off'.

 

Thanks guys for the tips...I'll check it out this weekend when I get some time...

Wanted to get this all wrapped up before winter...don;t want to have to run the AC to cool the car, LOL!!

I might pick up a cheap laser thermometer as well and check coolant temp (outlet hose)...