Yeah ..an old Diesel..

Like I said..you pulled one from an old system car...simple.

If ever in doubt, just simply look up the part for the car in question and the part site will tell you if the sw is a pressure sw by footnoting the cut-in PRESSURE spec in BARS...and if it is in BARS, you can be assured it is reading those BARS from the refrigerant reservoir/system. NOT the temp of the drier.

The reason behind all this is . of cours, a temp reading is NOT an accurate reading of HIGH SIDE PRESSURE..it is a GUESS, at best.

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A Dalton

Thanks Arthur. Maybe you can save me some time in the parts catalog, do you know if the 83 380SL is temp or pressure? I need to change it hopefully without having to recharge.

Dan

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81 240D 4speed with 300D engine
87 560SL
2005 E320
Yukon Denali
Sierra Denali
850 Turbo Volvo
1996 Mustang
1984 Mustang race car
3 Boats

Save you time ????, when the parts page is right on top of the Forum page you are ON ??

This must be a "Call Center".

Here is your Diesel sensor, and as you can see , it is not a pressure sw

http://catalog.peachparts.com/ShopByVehicle.epc?q=1983-Mercedes--Benz-300d-Climate--Control&yearid=1983%40%401983&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6191%3AMBC%7C1504%3AED%7C10000135%40%40300D&catid=242213%40%40Climate+Control&subcatid=242240@@A%2FC+Temp%2E+Switch&mode=PA

But your 380sl IS a PRESSURE sw and MY POST diagnostics know the difference on models using a high side pressure sensed system..

..so anyone who cares to doubt that, get ready to lose your refrigerant ..

Here is the sensor I was referring to for the original posters diagnosis..as you can see by the hole and gasket, this is a pressure switch and requires evac to change ..unless you are Real Fast...
Click on the pic for a ZOOM pic and you will plainly see the difference between the two.
It's always a good idea to do a little homework before jumping into a thread where the guys that are discussing the technical aspects of a particular chassis have worked on Benz products for nearly 50 years..

http://catalog.peachparts.com/ShopByVehicle.epc?q=1992-Mercedes--Benz-190e--.3-Climate--Control&yearid=1992%40%401992&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6131%3AMBC%7C1485%3AED%7C10000009%3ASM%7C846%40%40190E+2%2E3&catid=242213%40%40Climate+Control&subcatid=242240@@A%2FC+Temp%2E+Switch&mode=PA

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A Dalton

Arthur Dalton, yes, I did the pigtail jump test and the fans did not come on. Thats why I wanted to check the wire going to the resistor. Right? Remember, the high speed works comming on about 107C. I let I idle to that temp to make sure they came on. The ac seems to work fine. It has a rebuilt compressor a year ago. I know the low speed was working about a month ago

The fuse looks good, also, I changed out the relay with a new one. No luck. The fan didn't come on. That's why the wire to the resistor in next. Right?

Very Good

Here is the nxt test step in diagnosis.

Key ON , engine not running..

As you jumper the pigtail wires again, listen by ear right behind the fuse panel, That is where the low fan relay is..
If you hear the relay clicking, then y0u know the feed circuit and relay coil side are OK and that your problem is on the LOAD side of the circuit.
That would be the fuse or the R15 resistor/wire.

The R15 resistor is behind the driver side headlamp area. There are two wires on one side and a single wire on the other .

So , if wires are not burned off, here is that test:
[ if they are , you have found the problem]

Take a jumper wire from the battery POS terminal and touch the 2 wire side of R15 .that should get you HIGH fan.. [ which we already know is OK]..now touch the single wire side..that should get you LOW FAN ..if NO to LOW fan , R15 is bad. [ R15 is in series and that is how they get high fan down in speed to low]

This jumper test does not need KEY ON to do..

If no click on relay for first test, then bad relay fuse OR relay coil.
Remeber in all testing that there are TWO fuses ..one for the relays primary coil side [ sensor circuit] and another higher Amp for the LOAD sides [ fan motor/resistor R15 side]..if NO click on relay for first test, you know there is no power to coil side of relay and nothing will come on in that case.
That is why we look there first. If it clicks , we know LOAD side is suspect and next test is R15, specially in your case b/c you have high fan...which does not use R15...........only low fan uses R15.

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A Dalton

Here is what you are loking for

http://catalog.peachparts.com/ShopByVehicle.epc?q=1992-Mercedes--Benz-190e--.6-Cooling--System&yearid=1992%40%401992&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6131%3AMBC%7C1486%3AED%7C10000011%3ASM%7C847%40%40190E+2%2E6&catid=240909%40%40Cooling+System&subcatid=241010@@Aux%2E+Fan+Resistor&mode=PA

As you can see , there was a mid-year change b/c the orig ones open circuited due to ceramic incasement..the newer ones are open wire and not so effected by the high heat generation of the .2 ohm values.

If it is not behind headlamp, some of the earlier ones were up by the brake booster section.

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A Dalton

OK... I feel stupid, but I don't see the R15 resistor. What does it look like?

see post 22 ...............

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A Dalton

Duh..I see the link above with the photo

Found the resistor!!! AND.... The wire is FRIED. Thanks so much

Very Good

As D Poole said, a very common fault on a low fan complaint, specially when the jumper test fails.
The new type Resistor cuts down on the heat and helps alieviate that condition, but it still happen over time on cars that get a lot of ac use...those fan motors can draw 25 Amps [ even more w/age] ...quite taxing on the small wiring for the low fan, whereas the high fan has much bigger wiring [ 4.0mm vs 2.5mm]
Now you know step-by-step diagnosis for any fan condition.......

..ya did good................

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A Dalton

I might also add that I use a mod with a simple relay that will allow elimination of the R15 circuit ..this mod gets you high fan instead of low fan for a/c condenser air-flow..a much better arrangement on these marginal a/c systems.

One simply takes that wire that burned off the R15 and brings it to a relays coil side as a low amp trigger signal instead of the load feed to R15, and then use the relay 30/87 load contacts to do the switching of the load to the other side of the R15. [ which already has the heavier wiring for high fan circuit/draw]... .this simple mod not only gets you a better a/c system output in traffic, etc., but it also eliminates any futher R15 burn-ups.............. [you are still using the low fan components..relay/fuse/sensor]
I have an article about it in the Archieves, if anyone is interested...............
The principle here is the more airflow across the condenser with a slow/non moving car, the better the a/c will perform...cond A/F is as important to performance as the evap......the cond has to dump the heat the evap has absorbed, so the more air , the better.........best bet is better/bigger cond, but I have found this circuit trick to work well for short $$$$..which is always a concern of my mods.

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A Dalton

Excellent . helped me rectify the fan fault
mak .

Very Good..
..glad someone reads/uses this stuff...

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A Dalton