Howdy. I changed employers, and as a result, changed driving patterns.

I recently became painfully aware that my AC does not cool my car unless I am flying down the highway. OK. that's an exaggeration. But it definitely does not cool when I drive a mile to pick up my daughter, and wait in line at the school.

I got out and checked the ACC fans on the front of the radiator. No movement. Outside temp was close to 90* F, dash fan was blowing strong. If my drive takes me to the highway, or at least on a road where I can go 35-40ish, then I don't really notice an AC issue.

I have been searching for threads related to this. My electrical skills are not good. I am not clear on instructions like " jump the wires connected to the pressure switch with pigtails on the AC drier". Does this mean bypass the switch by connecting the two wires directly? Same question for "jump the wires in the 2-pin connector". Also, where do I find the pressure switch? Or the AC drier?

Thanks!
Tom Lynch

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2016 E350 4matic wagon
2010 ML350 Bluetec
1995 E300D Gone, but not forgotten.

Yes that is exactly what it means. You are taking the switch out of the loop.

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1987 300TD 309, xxx 2.8.2014 10,000 mile OCI


Be careful of the toes you step on today, as they may be connected to the ass you have to kiss tomorrow. anonymous

“Be who you are and say what you feel, because those who mind don’t matter, and those who matter won’t mind.” Dr. Seuss

Thanks, Bio!

Now, where do I find the switches to bypass?

Tom

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2016 E350 4matic wagon
2010 ML350 Bluetec
1995 E300D Gone, but not forgotten.

Tom, the temp sensor up in the front of the head can cause this as well. I forget the value of resistor to stick in there to get it to work. That was my prob.

The switches they refer to are near the compressor, and plug in right where the site glass is.

Thanks, Gene!

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2016 E350 4matic wagon
2010 ML350 Bluetec
1995 E300D Gone, but not forgotten.

The fans will come on high when the temp switch on the engine is shorted/bypassed, which shouldn't normally occur until the engine coolant exceeds the turn-on temp (105*C?) and has little to do with A/C use.

The high-pressure switch on the receiver/dryer when shorted (on) will turn the fans on low, through the resistor mounted near the receiver dryer. This is what you usually see with A/C operation BUT, it only turns them on when the pressure in the A/C system reaches the high-pressure threshold which requires: enough heat in the R-134a (sounds like you have that) AND enough R-134a. If the system is low on refrigerant, the fans will never turn on.

I suggest shorting across the high-pressure switch on the receiver/dryer, if the fans work (usually do) then you need to check refrigerant pressures.

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Gone to the dark side

- Jeff

Thanks!

Maybe this next weekend I can get under the car and figure out where the switches are, and get to jumping.

Tom

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2016 E350 4matic wagon
2010 ML350 Bluetec
1995 E300D Gone, but not forgotten.

Not under, on top. Filter-dryer is ahead/under the ABS pump, temp switch is on the outlet pipe from the head.

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Gone to the dark side

- Jeff

Thanks for the directions!

Tom

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2016 E350 4matic wagon
2010 ML350 Bluetec
1995 E300D Gone, but not forgotten.

It may just need a little r134a. Do you have some gauges you can put on it?

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Jim

No gauges. I do have wire I can use to jump. Won't be hard to find a shop to check pressure, if the other tests point that way.

Thanks!
Tom

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2016 E350 4matic wagon
2010 ML350 Bluetec
1995 E300D Gone, but not forgotten.

In the summer heat I am again mindful of lack of cooling without car movement. Yes, I have not addressed the issue I had last year, and that means I am lazy (probable), or overworked (not impossible).

My blower motor recently failed, and I just had it replaced. Did you know that there are three different blower motors for a 1995 E300D? I thought there were two that were similar size, but with different connectors. There is a third one that has fans further apart and larger diameter. The cross reference feature on parts-selling websites may say that it is a fit for any 1995 E300D, but it is not. If you are fiddling with a '95, check using the VIN.

I asked about the accessory motors while the mechanic was under the hood with the blower. Apparently there is power at the fuse, but not at the relay behind the headlight. Without power downstream from the relay, jumping at the switches didn't work.

Looks like I get to spend some quality time with a meter on the driver side wheel well, and also possibly jumping from battery to fans to see if I have one problem masking another.

Regards,
Tom

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2016 E350 4matic wagon
2010 ML350 Bluetec
1995 E300D Gone, but not forgotten.

pop the hood, and remove the two pin plug next to the fuel filter with key on or engine on, the front fans should run at high speed. If they are then the fans are good and the wiring is good to the fans.

If they dont go - follow

1 - raise hood to service position
2 - remove fuse panel and expose relay box by removing the screws
3 - there are two relays on the edge - one blue one green, blue is low speed and green is high both have fuses in them remove relays and check the fuses - if blown replace them
4 check fan operation by removing connector - if they dont work - then follow

1 the main fan connector is beside the radiator in a metal cradle on the chassis leg, remove the plugs and see which wire is brown, test the brown wire to body ground (it is grounded on the ABS pump bracket) - test the other wire to continuity at the resistor (test the side closest), if you dont get continuity - your wiring from the resistor is burnt which is normal for this car. remove headlamp and repair the wiring, you might need to change the resistor too as the lugs and nuts weld themselves to the screw posts renderring it useless.

If you see continuity to the resistor wiring, then you need to feed the fans power from the connector to see if they are good to run.

To check low speed A/C function the drier bottle ahead of the resistor has a switch on it with 2 brown wires with spade connectors, remove and join the body side together the low speed fans should work if the resistor and wiring is good. You might also want to test that one wire of what you are shorting actually has body ground, it is also grounded to the ABS pump bracket.

All this aside - the A/C function is also dependant on the main engine fan - it should clutch up from the transferred heat of the condenser. The engine fan can pull insane amounts of air. the front fans are only to provide some flow when the car is idling.

the blower motor difference is the little pig tails on the motor wiring and the smaller dia but wider fan wheels due to the airbox having filters.. You can solder your old wire pigtails to the old style motor and cut off the spade connectors on the motor then transfer the fan wheels over. - you would need a high wattage solder iron as the lug you are soldering to is very thick.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Thanks, Zulfiqar!

I appreciate the detailed troubleshooting sequence.

The car is delightfully cool when moving much at all. Sitting at idle is my only problem point.

I recall you had a thread about blower differences. I was too trusting that the vendor had me taken care of.

Regards,
Tom

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2016 E350 4matic wagon
2010 ML350 Bluetec
1995 E300D Gone, but not forgotten.

what temp does the engine operate at idle?
I ask because the fan clutch should handle the cooling loads of the a/c most of the time, and the aux should only come on during lulls between rad temp needs.
you should test your fan clutch. get the car up to temp, pop the hood and see if you can gently jam a rolled up newspaper in the fan (GENTLY it's a plastic fan blade) and stop the blades, or does it shred the paper? at full temp on the motor, the fan blades should operate FULL pressure, and they should shred the rolled up newspaper.
odds are good the fan clutch is weak. (they don't last very long really, and it's a good idea to test and replace/rebuild them every 3-5years.

also, the cleanliness of the condenser will have a GREAT impact on the cooling capabilities of the car!

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!