When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
86 Camaro 305. Computer removed by previous owner. Cooling fan will not activate on its own when engine gets hot. I can’t say I have verified to temp of engine but it’s has been pegged in the red…hot! I replaced cooling temp switch in block (located between 6 and 8 behind dipstick) with a Duralast SW 500…then replaced that with a Duralast 505. Checked ground between switch body and engine block, block and frame, and frame and negative post on battery. Bought new relay located on firewall driver side. New switch connector. Cooling fan comes on when switching to A/C on heat/air conditioning control panel. When I jumper the cooling fan connector to ground the cooling fan starts up…with either the car running or just when ignition switch is on. The A/C does not work in this car if that makes a difference. My understanding of the switch is that when it closes it completes the circuit and the fan should run…as it does when I ground the switch connector. Another bad switch? Grounding problem? Not getting it…
Sounds like you've narrowed it down to bad switches. You can check continuity between the terminal and switch body in with a hotplate. Obviously boiling water won't exceed 212.
Sounds like you've narrowed it down to bad switches. You can check continuity between the terminal and switch body in with a hotplate. Obviously boiling water won't exceed 212.
2 bad switches? Doesn’t seem right. I just didn’t know if I was missing anything in the way it’s wired. Guess I’ll try another switch but I have my doubts. Maybe buy a “cooler switch” that I can bench test first.
This fallacy is repeated ad nauseam by people who didn't pay attention in high school chemistry, physics, or biology class. It is just WRONG.
PURE water, AT SEA-LEVEL ATMOSPHERIC PRESSURE, boils at 212°. ANY OTHER kind of water, at ANY OTHER pressure, boils at SOME OTHER temperature.
Coolant in an engine is, or at least should be, somewhere around 50/50 water/AF, to 70/30. The water is NOT pure in your engine. Impurities raise the boiling point as well as lowering the freezing point. (extend the range of temps of liquidity in both directions)
The pressure in a cooling system, as printed on the radiator cap, is something around 15 psi or more. Increased pressure has a YYYYYYUUUUUUUUUJJJJJJE effect on boiling point: doesn't affect freezing hardly at all, but raises the boiling point ALOT.
BOTH of these factors DRASTICALLY affect the boiling point of COOLANT as found in AN ENGINE. Together, they render 212° ... LAUGHABLE.
In point of fact, a typical water/AF mixture at 15 - 18 psi, boils at around 260° - 275°. The fan coming on in the 230s is COMPLETELY NORMAL, and coolant WILL NOT be boiling at that temp, if the system holds pressure and has the correct coolant mix in it.
OP, IGNORE all the crap about 212°, because IT DOESN'T APPLY TO AN ENGINE. Rather, sounds to me like, your gauge is inaccurate. Your car should run about 205 - 210° driving down the road, long-term; sitting still idling, the fan should come on at the fan sw set point, and turn off at that set point (usually around 20°F different). I'd suggest using your infrared temp gun to check the ACTUAL temp and see if the gauge is right, rather than stress over "overheating" that probably doesn't exist.
Who knows, the op may be driving at 27k ft above sea level and the coolant mixture will absolutely boil at that elevation.
best way to think about these cooling systems are pressure cookers and altitude!
seriously though, I'd check the actual temp. The factory gauges are at best so-so. Mine was accurate around 180 deg and exponentially decreased in accuracy from there up. Once you start modding the car enough, some better gauges are ideal.
This fallacy is repeated ad nauseam by people who didn't pay attention in high school chemistry, physics, or biology class. It is just WRONG.
PURE water, AT SEA-LEVEL ATMOSPHERIC PRESSURE, boils at 212°. ANY OTHER kind of water, at ANY OTHER pressure, boils at SOME OTHER temperature.
Coolant in an engine is, or at least should be, somewhere around 50/50 water/AF, to 70/30. The water is NOT pure in your engine. Impurities raise the boiling point as well as lowering the freezing point. (extend the range of temps of liquidity in both directions)
The pressure in a cooling system, as printed on the radiator cap, is something around 15 psi or more. Increased pressure has a YYYYYYUUUUUUUUUJJJJJJE effect on boiling point: doesn't affect freezing hardly at all, but raises the boiling point ALOT.
BOTH of these factors DRASTICALLY affect the boiling point of COOLANT as found in AN ENGINE. Together, they render 212° ... LAUGHABLE.
In point of fact, a typical water/AF mixture at 15 - 18 psi, boils at around 260° - 275°. The fan coming on in the 230s is COMPLETELY NORMAL, and coolant WILL NOT be boiling at that temp, if the system holds pressure and has the correct coolant mix in it.
OP, IGNORE all the crap about 212°, because IT DOESN'T APPLY TO AN ENGINE. Rather, sounds to me like, your gauge is inaccurate. Your car should run about 205 - 210° driving down the road, long-term; sitting still idling, the fan should come on at the fan sw set point, and turn off at that set point (usually around 20°F different). I'd suggest using your infrared temp gun to check the ACTUAL temp and see if the gauge is right, rather than stress over "overheating" that probably doesn't exist.
OK…I will check it with an infrared within a couple of days. I have driven this car for the last couple of weeks trying to get the cooling fan to auto engage using the fan switch…hard to believe I can get it any hotter than it has been. You are right…running down the road the temp stays below the 220 degree mark…heats up in stop and go and running it through the gears…into the red eventually at lower speeds. You would think that at some point (here in AZ heat) the fan would kick on. I’ll let you know what I find out. Thanks for your input…
Who knows, the op may be driving at 27k ft above sea level and the coolant mixture will absolutely boil at that elevation.
best way to think about these cooling systems are pressure cookers and altitude!
seriously though, I'd check the actual temp. The factory gauges are at best so-so. Mine was accurate around 180 deg and exponentially decreased in accuracy from there up. Once you start modding the car enough, some better gauges are ideal.
I will be comparing actual temp to gauge temp soon. But I have idled that car in the garage a long time trying to get it hot enough to engage the fan through the switch. Hopefully find something out soon. Thanks for the response…..
Sounds like a factory gauge that ready too high. Mine would read 260 when my factory switch came on at 235. Grab a 1989 turbo trans am switch comes on at 212 and off at 195 and measure temp with the temp gun.
If you need to because the PO screwed up the car with the computer delete downgrade you can always wire up a relay and make your own circuit
Sounds like a factory gauge that ready too high. Mine would read 260 when my factory switch came on at 235. Grab a 1989 turbo trans am switch comes on at 212 and off at 195 and measure temp with the temp gun
Thanks for the info…
I’m going to run the temp up tomorrow afternoon and check with infrared thermo. The Duralast 505 I just installed is rated on at 213. I believe that what everyone is saying about the gauge being off is true…I just got nervous about overheating the engine…it sure seemed hot! Thanks for the info. I’ll let you know of the results👍. I have an 81 Camaro 305 that I put a backup temp gauge in when I first bought it because I didn’t trust the gauge in that car at the time. Eventually got it to work with some new parts. You’d think I would have learned…
Before doing anything else, obtain an inexpensive Infrared temp gun (can be had for less than $20.00) and see if the engine is actually overheating.
That has been discussed earlier. My A/C guy is coming over later to do a checkup on house A/C and I’m going to check coolant temp with his equipment. I anxious to see the results…
I purchased an infrared thermometer and took readings on the thermostat housing. The cooling fan did engage at 235-238 degrees and disengaged at 220 degrees. The temperature gauge (in the car) is reading over the 260 degree mark but drops slightly after the fan runs a few minutes…although it is still in the red. A Duralast SW 505 is the coolant fan switch currently installed. That still seems to run a little hot to me but with the temp variance of the infrared thermometer maybe it is ok. Any opinions on that?
I noticed they sell aftermarket temperature gauges online. Anybody know if these are an accurate replacement or do people get the original gauges calibrated somewhere. I can’t drive around with that needle in the red😬.
I would like to thank Ratfink6923, Sofakingdom, Firechicken, Midias, and Ironwill for steering me in the right direction for this problem. Sofakingdom was right…I was stressing over something that wasn’t a problem…
I had it in my mind that it was more of a circuit issue and disregarded some of the other obvious signs. Thanks again…
I have an autometer gauge cluster in my car. The gauge is really accurate. It's always with in 5 deg of the separate sensor reading for my EFI. Thats in a slightly different spot. That said I don't know if you wanna deal with new gauges. You may be able to get a new sender/gauge that's in better shape.
As far as the temp being a little high, there are other guys who have stock cars and more knowledge about stock temps.
Try a new temp gauge sending unit first. Driver's side head, same hole as the fan sw, just, the other head. (head castings of course are interchangeable side-to-side) Between #1 & #3 spark plug hole.
I would like to thank Ratfink6923, Sofakingdom, Firechicken, Midias, and Ironwill for steering me in the right direction for this problem. Sofakingdom was right…I was stressing over something that wasn’t a problem…
In order to solve a problem, you first have to identify it. You can solve EVERY OTHER problem there ever was, but if THE ONE you're suffering from isn't identified, you'll probably NEVER be able to solve it, aside from pure dumb luck. Which is something I have NONE WHATSOEVER of, therefore I've developed the discipline over the years of not depending on it.
The temperature gauge (in the car) is reading over the 260 degree mark but drops slightly after the fan runs a few minutes…although it is still in the red.
The gauges in 3rd gens are notoriously inaccurate and are only of value for 'relative' readings rather than absolute readings.
I noticed they sell aftermarket temperature gauges online. Anybody know if these are an accurate replacement or do people get the original gauges calibrated somewhere.
The better-quality aftermarket gauges are indeed accurate, but you'd be altering your car to install them; if originality isn't your concern, consider them. As far as 'calibrating' the original gauge, IMO that isn't a possibility.
Right: about the only "calibration" there is for factory gauges, is in the sending unit and its tolerance. They're REALLY crude. Butt because of how they're made it's also REALLY hard for the gauge itself to fail "inaccurate": they tend to either work, or not. Not a whole lot of middle ground.
If you REALLY want it to be "accurate", buy a handful of SUs, and install the one that makes the gauge read the closest to your IR gun, at the temp you're interested in since they're also not particularly linear.
Personally I'm used to them being not very accurate. All I really care is, is it reading what it always does ( = nothing has changed), or is it suddenly reading something different ( = better check it out). The absolute "number" on the gauge is largely irrelevant.
You can solve EVERY OTHER problem there ever was, but if THE ONE you're suffering from isn't identified, you'll probably NEVER be able to solve it, aside from pure dumb luck. Which is something I have NONE WHATSOEVER of, therefore I've developed the discipline over the years of not depending on it. 
