If I wire my Aux fan to be always on...
 

If I short the switch on top of the receiver/drier so that my aux fan is always on, would that cause any problems? Would my A/C work as normal? The only thing I can imagine might be the problem is it'll shorten the life of the fan. Any issues with battery drain?

If any of you guys have been following my threads. My car is running too hot. Need a temporary solution.

It would reduce the life of the fan for sure. When running the AC on high with the headlights and foglights on the battery voltage might drop below normal at idle.

Why is it running hot? I doubt that little fan is gonna keep it much cooler if you have a problem.

It should not be a problem. I hot-wired the aux fan on my 300SDL from Vegas to San Diego when the car overheat. There are a lot of aux fans from gasser in the JY, so do not worry about the life span of it for now.

You really need to measure the temperature of the engine and compare it to the gauge. You do not know what is going on without that info. It seems that the old sensor is giving a more 'realistic', not necessarily right, temp than the new one. I do not have my 300D with me as it was driven up to Santa Cruz on Monday, otherwise I could do some measurements for you.

I hope other members can supply you with some resistance value using their cars. I would expect any W123 uses the same sensor.

It seems that my SDL also uses the same sensor. I can give you a rough resistance measurement tonight at 85C and ambient temp.

I've wondered this as well. The only worry I have is that it the electric fan would be starting up during cranking. Sometimes you need all amps on deck with these things :D

Ya. Wiring a switch would be ideal. Anyway, it's summer. I'm sure our cars can handle it. :)

PO of the red car fashioned a jumper and kept it across the aux fan leads during summer to help cooling at idle in Houston traffic. I have the system working better now, so I don't use it. Never had a problem cranking, and the fan is still going strong 4 years later. My biggest problem with it was that it was so loud all the time.

ah-kay. I will purchase the ir gun this weekend. I don't understand why I can't get a stable reading. The reviews of the one I have aren't bad.

Are you telling me if you hold the gun and point it next to the temp sender and keep the "scan" button pushed, you get a solid reading? Mine jumps around 10 + or 10 - C. It's black with oil in that area. I should be getting a solid reading. I'll try again...

Zeke. I don't mind that it's loud. Brooklyn is already loud. :)

No measurements yet as I am still at work. I am on PST time. Why don't you try this?

1) Tape a masking tape over the side of a pan and heat water until boiling.
2) Point your IR probe to it and it should read solid 100C.
3) Point to the stove, if electric, and get a reading.
4) When you point to the engine block, it has to be clean and non-reflective, as the laser works by absorption and reflection by the object.
4) You can also point to the top of the radiator which is matt finish and should give a steady ready. Or point to the sensor itself, tape a masking tape over it.
5) A dirty or oily service probably would not work.

You may not need a new probe, may be it is the battery.

It's gas. Ok I will boil the water now and try it with the masking tape. I'll post my results.

My results... http://www.youtube.com/watch?v=HDNt-m6-SPw excuse the mess...

Maybe I'm too close or too far... I mean some of the reading was solid but then changed. I have an air conditioner and fan close by. Maybe that's what causing it.

What, precisely, is the function of the laser portion of an infrared thermometer? Are you suggesting that the laser plays a role in temperature determination?

I'm trying to follow what's happening, but I'm confused.

You replaced the temp sensor for the gauge. That didn't initially work, but now it does and maybe reads correctly - or at least close to the IR gun temp? And that temp is approx 100 C?

But you also had a coolant leak after the temp sensor swap that may/may not have been a loose overflow cap? And when it was loose or leaking the temps were lower on the gauge?

But...you've also killed a battery with leaving your lights on, so I'd be leery of doing something that a) reduces your car's ability to keep the battery fully charged and b) adds a load to the electrical system on start-up.

So...yes, a simple fuse or insulated wire across the receiver dryer temp switch will jumper an otherwise working aux fan that will help reduce temps. Other members have posted they have no negative effects and the fans don't die an untimely death. I wouldn't recommend it as a permanent solution.

I'd recommend clarifying what's been done, what the current status is, and maybe try the nose high burp technique and turn your heater on high to try to get flow throughout the system to eliminate air.

I'll clear things up...

The new temp sensor doesn't work. I swapped the old one back in. it works but I don't know if the temps the gauge is showing me is correct.

When I installed the new temp sensor, I went for a drive and it took about 15mins for the car to get to 50c which is very odd. I believe it was a combination of the high temps and the loose cap.

I got myself a new battery. The old battery wasn't holding a charge anymore.

What has been done about the temps is this...

I first drained the green stuff.
I was going to change my thermostat at that point but that's when the bolt snapped on the housing.
I then added the good MB stuff.
About 2 weeks later I replaced the whole thermostat housing and put in a new thermostat.
Today I changed my temp sensor but it didn't work. So I put the old one back in.

I guess next I need to check my radiator and water pump.

IR guns
 

If you want an accurate reading from your IR gun you have to paint a flat black spot on the surface to be measured. the readings will be off by 10-15 deg or more if you don't. The IR gun is expecting an emissivity equivalent to flat black. I use this in my work with boilers and steam systems all the time. Cheers Dan

Ok so pointing it on the top of the radiator should work? I will try that tomorrow after installing the sway bar link.