1985 190E Troubleshoot A/C clucth
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Ignatz:
Frist, thank you for the response. I bought the car about a month ago and the A/C wasn't running when I got it. I don't know how long the A/C has been out. I will check the voltage at the compressor. I think I know how to check it. There are several posts on that issue. I will get back to you as soon as I can.
Once again, thank you for your time and efforts.
Frist, thank you for the response. I bought the car about a month ago and the A/C wasn't running when I got it. I don't know how long the A/C has been out. I will check the voltage at the compressor. I think I know how to check it. There are several posts on that issue. I will get back to you as soon as I can.
Once again, thank you for your time and efforts.
The clutch itself rarely goes bad, but it can. I have a spare clutch which I can offer you. But it won't do you much good, because you really can't get it apart on the car. If you were going to remove the compressor to replace the clutch, you may as well go for a whole new compressor.
There are a few things that can keep the clutch from engaging. Actually, it's a pretty long list:
1) Low freon pressure, which can itself have many causes.
2) High freon pressure (there's always the idiot who thinks more is better).
3) The high/low pressure switch on the receiver drier. There is a single switch that performs both functions. (the other switch on the drier operates the fan)
4) The speed sensor on the back of compressor. The speed of the compressor is continuously compared to the speed of the engine. If they differ, the clutch is disengaged to prevent the belt from snapping.
5) The engine speed sensor on the bellhousing.
6) The Klima relay. The Klima relay is a complicated bit of electronics which is where engine and compressor speed is monitored. It's behind the battery, you have to remove the plastic "firewall" to access it. If the Klima relay is bad, you won't have a downshift when you step on the accelerator, because that's one of the things the Klima controls.
7) A shorted fan switch on the engine outlet.
8) The in-cabin components of the HVAC system, including the head unit and temperature sensors.
That's a pretty heavy list. I guess the place to start is to verify freon pressure.
There are a few things that can keep the clutch from engaging. Actually, it's a pretty long list:
1) Low freon pressure, which can itself have many causes.
2) High freon pressure (there's always the idiot who thinks more is better).
3) The high/low pressure switch on the receiver drier. There is a single switch that performs both functions. (the other switch on the drier operates the fan)
4) The speed sensor on the back of compressor. The speed of the compressor is continuously compared to the speed of the engine. If they differ, the clutch is disengaged to prevent the belt from snapping.
5) The engine speed sensor on the bellhousing.
6) The Klima relay. The Klima relay is a complicated bit of electronics which is where engine and compressor speed is monitored. It's behind the battery, you have to remove the plastic "firewall" to access it. If the Klima relay is bad, you won't have a downshift when you step on the accelerator, because that's one of the things the Klima controls.
7) A shorted fan switch on the engine outlet.
8) The in-cabin components of the HVAC system, including the head unit and temperature sensors.
That's a pretty heavy list. I guess the place to start is to verify freon pressure.
I have a 1986 190d, I'm quite sure there is no freon in the system(I do have service record of it being converted to the R134a system). The electric fan on the front of my radiator does not turn on when the AC controls are engaged. The blower pushes air, just luke-warm/warm air.
Would having no freon and therefore pressure in the system cause the Aux fan NOT to turn on?
Would having no freon and therefore pressure in the system cause the Aux fan NOT to turn on?
Chase, on my '89 190E the aux fan activates when the car begins getting hot (above 90 on the temp gauge) not immediately when the AC is first switched on. Not sure if this is how it's supposed to work but that's what my car does in case it helps.
Same here on my '93 190E. If I start my engine while parked with the A/C on, the aux. fan won't start running unless the engine temp. rises (via 2 prong temp switch), or if the A/C high pressure rises. Usually it's the A/C high pressure switch that activates the aux. fan first, then just cycles like it's suppose to.
When my A/C stopped working correctly, it turned out to be a blown aux. fan fuse. I hooked up my A/C gauges and when the high side got too high the aux. fan failed to turn on. So that led me to the blown fuse.
Let's clear up how this works. There is a pressure switch in the receiver/drier that activates the low speed fan relay. It comes on at 300PSI, which is usually above the operating pressure of the a/c system. But you can hit that on a hot humid day. No freon, no pressure, no fan. If your fan comes on at low speed at any other time, there is a problem. If it never comes on with a/c operating, then check the fan resistor on the right inner fender.
High speed is activated by high temperature, usually at 105, sometimes higher. This should almost never happen. Depending on year and engine, it's either activated by a thermal sensor which feeds the climate control system, or directly by a thermoswitch located on the engine water outlet. The high speed relay is sometimes mounted in an auxilliary fuse box just forward of the main fuse center. It's always an internally fused relay. If it's a black relay, the fuse can't be replaced and the relay will need to be discarded if it blows. Replace it with the later style orange relay which has an ATC fuse on top.
The belt driven fan has a clutch which can either be electromagnetic or viscous. Either way, it activates around 95c.
And that's about all there is to 190 fans.
High speed is activated by high temperature, usually at 105, sometimes higher. This should almost never happen. Depending on year and engine, it's either activated by a thermal sensor which feeds the climate control system, or directly by a thermoswitch located on the engine water outlet. The high speed relay is sometimes mounted in an auxilliary fuse box just forward of the main fuse center. It's always an internally fused relay. If it's a black relay, the fuse can't be replaced and the relay will need to be discarded if it blows. Replace it with the later style orange relay which has an ATC fuse on top.
The belt driven fan has a clutch which can either be electromagnetic or viscous. Either way, it activates around 95c.
And that's about all there is to 190 fans.
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