1992 190E AC Question - PeachParts Mercedes-Benz Forum

meltedpanda · #1 04-30-2007, 11:41 PM

very cold for the first 5 minutes of operation, once the car warms up - compressor stops working, does not cycle on off - sound like low freon or compressor woes or niether

- hot here and need the air, why oh why don't I check these things out before I actually need them

brewtoo · #2 05-01-2007, 12:19 AM

Have you verified the belt tension is correct? If the belt slips, the compressor will shut down to protect the belt.

meltedpanda · #3 05-03-2007, 11:37 PM

belt tension OK , freon level good, the guy wh checked it indicated "probably electrical, just what I need to chase an electrical gremlin

Any common areas to look at here, fuses good as far as I can tell, it does come on. COuld it be the temperature ACC control ( blue /red dial ) ?
All input welcome!

slk230red · #4 05-03-2007, 11:51 PM

Quote:

Originally Posted by meltedpanda

very cold for the first 5 minutes of operation, once the car warms up - compressor stops working, does not cycle on off - sound like low freon or compressor woes or niether

- hot here and need the air, why oh why don't I check these things out before I actually need them

When my 190 was doing what you are describing, it was because the auxillary fan was not operating. The compressor was working, but the high pressure side got too high and the high pressure switch on the drier/receiver was turning off the compressor just like it was designed to do.
It turned out to be a blown fuse for the aux. fan. I replaced the fuse and the aux. fan operated. That was a few years ago and it is still working.

Dave

meltedpanda · #5 05-04-2007, 09:50 AM

I will check that out, thanks, where might this fuse be?
Should the fan come on when the AC is on?
Is there a way to check operation of the fan independent of the AC?

How does the main fan work and is it related, can it be tested? Is there a temp switch relay and where might that be.... so many questions so little time

Thanks for any input

slk230red · #6 05-04-2007, 10:30 AM

Quote:

Originally Posted by meltedpanda

I will check that out, thanks, where might this fuse be?
Should the fan come on when the AC is on?
Is there a way to check operation of the fan independent of the AC?

How does the main fan work and is it related, can it be tested? Is there a temp switch relay and where might that be.... so many questions so little time

Thanks for any input

The fuse is in the fuse box located behind power brake booster, (red fuse). There is a temp switch located on head behind thermostat housing. I think the aux. fan should come on when the A/C is on....I'll have to check.

meltedpanda · #7 05-04-2007, 01:00 PM

AC Condenser
AC/Refrigerant Temperature Sensor
AC Cutoff Switch
AC Evaporator
AC Expansion Valve
AC High/Low Switch
AC Relay

So which of these could be a culprit and once again , how do I check them?

slk230red · #8 05-04-2007, 03:02 PM

Quote:

Originally Posted by meltedpanda

AC Condenser
AC/Refrigerant Temperature Sensor
AC Cutoff Switch
AC Evaporator
AC Expansion Valve
AC High/Low Switch
AC Relay

So which of these could be a culprit and once again , how do I check them?

DON'T touch those items unless your aux. fan is working properly. Put a set of A/C gauges on your A/C system, you will see the high pressure side go up and the compressor will shut off if the aux. fan doesn't operate. The aux. fan cools the A/C condensor to keep the high pressure side in proper range.

So, step number one is to verify correct operation of aux fan.

You should have a 3 prong Temp. Switch that looks something like this. If you unplug the connector that goes on the 2 prongs and short them out at the connector, the aux. fan should operate. In theory, that is what the temp. sw. does...the 2 pins make continuity when the temp. reaches 110 degrees C.

lee polowczuk · #9 05-04-2007, 01:39 PM

sounds much like aux fans..

with the engine off....see if you can spin it freely with your hand... it could have locked up and fried a fuse...

gmercoleza · #10 05-09-2007, 10:50 AM

Just a tip, you might want to check your pressures because if the system runs for a while without the aux fans spinning it can lose some refrigerant out the pressure relief valve. As a result, though your aux fan now works, your charge might be a few oz. low. You won't notice until it's about a hundred degrees out...

meltedpanda · #11 05-11-2007, 11:00 PM

So here is the deal, I thought I had it fixed…….
I replaced switch after the shorting out method worked and much to my chagrin now it does not work .
Here are the symptoms
I do know the aux fan is working
With plug shorted everything works, fan, aux fan, compressor cycles on and off, responds to the temp dial, aux fan even shuts off after a time, turn it to max cool and it works fine
Connect to the switch and the electric fan stops, compressor cycles occasionally but not enough to cool
Now I am lost, all connections are secure, no bubbles in sight glass.
I need to take it on a trip, can I just short it out and make it work , is this a bad thing?
Could my pressures be the issue, It would seem that it should still work at least the electrical part.
Are there other switches I should check
Here is the other issue, the temp gauge never really goes above 85-90C, could that also be an issue, I thought the aux fan worked when the compressor got hot or pressure was high
HELP

meltedpanda · #12 05-12-2007, 05:17 PM

please

meltedpanda · #13 05-13-2007, 12:01 AM

does this have any connection to the temg sender,I noticed tonight that it went up to 80 C and then back down to 40C in 84 degree heat running at idle for 25 minutes
I have 7.5 v at the single plug is this correct?
I cannot get continuity through the other two no matter how hot the car gets, is it linked to another circuit?

slk230red · #14 05-13-2007, 01:08 PM

Are you stating that the aux. fans are not operating when the A/C is on?

If so, have you checked the aux. fan switch at the A/C receiver/dryer? There are 2 switches on the dryer, one for the freon pressure to shut off the compressor if the high pressure gets too high, and one for the aux. fans (this is the one with the pigtail). This one could be the one that is not turning on the aux. fan when the A/C is on.

Keep in mind that the aux. fan serves 2 purposes...
1. to cool the radiator when needed.
2. to cool the A/C condensor.

brewtoo · #15 05-13-2007, 01:10 PM

Quote:

Originally Posted by meltedpanda

does this have any connection to the temg sender,I noticed tonight that it went up to 80 C and then back down to 40C in 84 degree heat running at idle for 25 minutes

Are you sure it went back down to 40C? A properly functioning thermostat should not allow that.