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a/c fun with indy

1K views 14 replies 4 participants last post by  mrboca 
#1 ·
the a/c on my '98 e430 has been intermittent at best. i replaced the blower and regulator after that stopped working. managed to snag an upgrade from an '01 at my local pick-n-pull. i also checked and cleared the code from the dash control unit saying the auxiliary coolant pump (replaced with a new part) was bad.

a/c was still just cool so, i asked a well reviewed (yelp) shop to re-charge. they say the a/c fan module (located under the car, accessed through the wheel well) needs to be replaced. i'm wondering why this fault would not show on the dash control unit. does this unit control the fans in front of the condenser?

they ordered the part and when my wife took it for the install, they said it had the incorrect number of pins in it's plug. they'll order another and hopefully it's the right one.

anyone know of mid-year changes on this part? if they get the wrong one again, could it be adapted? i've not seen it myself but, think this is what they're talking about.

i was hoping this would be done with the recharge but, i'd just be happy to have it sorted before a road trip next week...
 

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#3 ·
To answer your question, for M113 engine 3/97 is the date they started using N65/1. Please see below.

I do not believe there is a direct fault reporting from the fan controller. to the a/c unit. It is detected by turning on the fans and interpretation of the refrigerant pressure and temperature changes.

Like the blower motor, the fan speed is controlled by pulse width modulation (in layman's terms, the power is pulsed with different pulse widths). And as it happens in a faulty blower motor controller, the fan controller may develop a fault that will not let the fan(s) turn at full speed, but let it turn at lower speeds.

You could have done a fan test by pressing the AUTO buttons simultaneously when the a/c is on for 15 seconds or more and check if the controller can deliver the full fan power.
 

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#4 ·
thanks for the tips, gents!

after a 3rd attempt the indy still isn't sure what's wrong. today, they installed the replacement fan control module and still no luck. after our road trip next week, i may do more reading here (learning how to read sensor outputs) and dive in myself.

i did the fan test per mrboca's advice above and they seem to run at "full blast". i notice while they're doing so, the ac gets cold like i'd expect. i'm thinking this might be a temporary work around next week (joshua tree, jalama beach and then morro bay)? as the weather shouldn't be hot, i'd probably only do so sparingly. any harm in running those fans like this?
 
#5 ·
I wonder what made your indy to think that the blower controller was faulty ? Most cars have a blower fan behind the condenser which turns on when the a/c is turned on. This is not so with your car. There is a visco fan (engine driven) that provides some air stream as required, so typically the front electrical fans get turned on in rare instances (when the refrigerant pressure is increased above certain level (14 bar at minimum speed or 20 bar at max speed)), or the engine coolant temperature is beyond certain temperature (95 degrees C). This conditions usually occur during hot days with start and stop traffic when there is very little air flow through the radiator / condenser.

If the fans are at full blast with fan test, I would say the fan controller is not the problem (you can verify this by looking at the sensor data menu, aux fan drive level, item-20 I think).

Your problem probably lies somewhere else, and with sensor value posting and error listing (if any) we may be able to figure this out.

Turning your aux fan from time to time should not cause any problem, apart from 25 to 30 amp current drain from your alternator. Use the recirculate button to maximize cooling. Depending on the problem, sometimes it helps to increase the rpm slightly, when stopping (with gear in P).
 
#6 · (Edited)
road trip went well (especially nice as i'd replaced the radiator, water pump and associated bits just prior...details in another thread), woulda liked to have working a/c approaching and leaving joshua tree but, temps were only in the low 80's. we do notice the a/c works for a few minutes every time we re-start the car (after fuel stops, etc.).

i was able to get into the "hidden menu" and read the sensor codes. car had been driven about 45 minutes prior and then parked in the garage on a lovely 70 degree afternoon. these were read with the car off, ignition in the "on" position;

1 - 82
2 - 78
3 - 87
4 - 84
5 - 148
6 - 168
7 - 07
8 - 96
9 - 27
10 - 2.1
11 - 3.0
12 - 4.3
20 - 3.2
21 - 32
22 - 00
23 - 32
24 - 11.2
40 - 164
41 - 32
42 - 08
43 - 152

should i have read these with the car running?

i'm ever so grateful for your thoughts on these, gents (&/or ladies?).

here are a few pics of the old girl (the car, that is...), providing the means for us to have yet another memorable road trip! by the way, we averaged between 24-27 mpg, often traveling at 75-85+! try that in an r.v.!
 

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#9 ·
took readings with the car running today. was about 75 in the garage (cooler outside), an hour or so after my wife had driven the car home;

1 - 75
2 - 75
3 - 60
4 - 64
5 - 139 (the evap. sensor - still out of whack compared to 3 & 4)
6 - 145
7 - 13
8 - 120
9 - 37
10 - 1.0
11 - 3.2
12 - 4.3
20 - 3.2
21 - 42
22 - 00
23 - 32
24 - 13.5
40 - 164
41 - 32
42 - 08
43 - 152

should i also take another reading before a cold startup? sounds like i'll need to replace that evap. sensor, i see 'em on ebay but, will check my local dealer for pricing too. i gather this is under the dash but, where exactly?

thanks very much for the advice so far. i'm feeling confident that with your help i can save yet another expensive trip to a mechanic!
 
#12 ·
thanks for that link, i have one on order from a sacramento warehouse, about $20. should arrive tomorrow.

on the install, i've learned you can reach from beneath or remove the instrument cluster and reach from above. anyone have a preference? the cluster removal videos make that seem a bit easier.
 
#13 ·
success! just came back from a 10-15 minute test drive on an 80 degree day and the ac remained on, eventually cooling the cabin as well as it ever has. i suspect there might be a problem somewhere as 67 degrees on the control unit is still a bit warm and i turned up the fan speed to keep cool but, fair enough...

i'm half tempted to bring it back to the indy at the start of this thread to let them replace the refrigerant and teach them how to read the codes...

i was able to pull the instrument cluster but, i have no idea how one would reach the evap. temp. sensor from above. it's not like my hands are even remotely trump-like but, i couldn't even get close. i was able to lower the cover beneath the steering column and blindly reach up to find it. the 2nd pic here helped (feel above the grey oval plug in the pic for the plug with 2 wrapped wires);

http://www.benzworld.org/forums/w210-e-class/1534921-evaporator-temperature-sensor-picture.html

here are the sensor values taken with the motor running at normal operating temps;

1 - 96
2 - 84
3 - 67
4 - 69
5 - 48 (here's the naughty one, was 139 before replacement)
6 - 150
7 - 13
8 - 120
9 - 39
10 - 6.0
11 - 3.0
12 - 4.2
20 - 3.2
21 - 42
22 - 00
23 - 32
24 - 13.3
40 - 164
41 - 32
42 - 08
43 - 152

mrboca & kajtek, thanks very much for your help here (& all over this place)! if i ever had the opportunity, i'd be more than happy to buy dinner or drinks!
 
#15 ·
Thanks for the offer, kind of you.. #7=13 bars seems OK to me, I have about the same reading under similar conditions. However, the #5 for my car goes as low as 36 degrees F, with #3 and #4 few degrees warmer than #5 when the cooling is in progress. If the inside air temperature sensor (where the front dome lights are) intake is partially plugged with dirt, it will read higher temperatures, as the indoor air sampling is impeded, and due to the heat pickup from the sun on the roof.

You may have some air and moisture in the system, especially if the a/c is not charged professionally. I would take it to a reputable a/c shop to get the refrigerant removed, vacuum the system properly, and then fill refrigerant per your car's specifications (by weight, which is specified on the label, affixed to the module box lid at the passenger side). Mine requires about 1 kg in weight. This would make sure that air and moisture are evacuated from your system, and you have the proper amount of refrigerant.
 
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