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.

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1984 300td euro turbo

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.

__________________
1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

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.

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

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

__________________
My occupational hazard bein'
my occupation's just not around...
1980 300SD
1980 300SD

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

__________________
1984 300td euro turbo

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.

__________________

Current Mercedes
1979 maple yellow 240D 4-speed

Gone and fondly remembered:
1980 orient red 240D 4-speed

Gone and NOT fondly remembered:
1982 Chna Blue 300TD

Other car in the stable:
2013 VW Jetta Sportwagen TDI / 6-speed MT

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.

__________________
1984 300td euro turbo

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.

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

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?

Yes.

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

That would be the wrong answer. The laser is just a pointer; it plays no role in the temp determination. It makes no difference if the laser is reflected, absorbed, sliced or diced.

Aiming. The visible red laser is colinear with the IR detector.

__________________
RIP:
2011 E350 BlueTEC, Schwartz 81k (totaled by uninsured drunk driver)
1964 Unimog 404.1 (wrongfully towed by the city)
1994 E320, Brilliantsilber 208k (transmission shuffled off after sudden catastrophic fluid loss)
1982 300D, Silberblau under a blue repaint 256k (sold for parts)
1995 E320 Polarweiss, 131k (sold for parts)
1995 E300D Polarweiss, 287k (totaled by drunk driver)

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

__________________
1984 300td euro turbo

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.

__________________
1984 300td euro turbo

The IR probe is probably good. You cannot measure the temp of the water with an open flame nearby. The open frame would create hot air and affect your reading. Turn off the frame and move the kettle to a table and do it again. It IR is a very sensitive instrument.

Measurement from my SDL.

At 82C the resistance is about 330 ohm
At 25C the resistance is about 2000 ohm.

I think you new sensor may be correct.

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.