Loosing Power to Fuse 11 AC System/Blower Fan and Compressor Clutch

[LNGfish]

1982 300SD

TY for Reading.

This is the 30 amp fuse that is for the Fan Blower and the coil for the Clutch Coil on the compressor. It might power other things.

This fuse holder was removed out of the factory box a few years ago and I used an External 50A fuse holder and down graded to a 30A fuse for the sytem. So it is at factore specs.

This has been fine for a couple of years.

Compressor coil not engaging, energizing. No voltage at coil.

Runs ok if voltage is jumped to coil.

Today, using a voltmeter I noticed voltage drops from 14 V to 0.0 V when ever there is a load put on this circuit. ie "simply installing the fuse", with sytem on max cold, the voltage drops off to zero. There is no big sparking so it is not load related, more of a power supply problem.

I need to know where this voltage/current originatessfrom. I'm assuming the Push Buttons, but I;'m not sure. I see the wire run down out of the bottom of the fuse box.

Please give me an idea of how to get to where this wire goes so I can check for a loose connection, hoping.

I have never removed the AC brain, or ever seen the push buttons assy, so some brief help would be appreciated to work in this area so I don't mess up the wood.

Thanks for any help.

Anyboy have Roys phone number or email addy?

Steve

[pmckechnie]

Steve, Going by my 84 500SEL if you are checking the power at the fuse F11, then it comes from the ign switch on a RD/YL wire. I think the 82 300SD and 84 500SEL would be close as they are both gen one cars. The push button unit energizes a compressor relay and the relay supplies the power to the compressor. the fan gets its power from the electronic unit for blower speed control. It gets it's power from the same F11 and Ign switch circuit.

Does this help any?

Paul

[LNGfish]

Paul,

OK so this whole thing is powered from ignition switch. Thanks for the reply. Yes I rembemeber it to be Rd/YL. I will look tomorrow. I wonder if it could be a loose screw where it connects to switch. Do you know?

[LNGfish]

I was wondering of what I might expect to find at the electrical assembly, switchassembly, on the back of the ignition tumbler. I had once had a bad one on a Chevy and it was replacable. Are these replacable on a MB?

thanks

[LNGfish]

This is getting werid. Today it appears as though the voltage/good current is back to fuse 11. So looks like ignition switch is passing current good today. So now I have back the Voltage to fuse 11 today and the fan and AC controls working good on dash. Fan speed ramping up fine, etc.

I did notice freon was low so I added 2 small cans.

Now the only problem that I have is the compressor is not getting voltage.

I jumped it with a fused hot wire to charge it up. I can't seem to find the LP Cut off switch that I normally see in AC systems.

What would be the next step to get voltage back to the coil on the compressor clutch?

Previoius guy said it was powered by a relay. Not sure where to look.

Thanks for any help.

[Brian Carlton]

Hi Steve,

The electrical schematic isn't quite accurate in the wiring to the clutch and I need to check the climate control manual when I get home tonight.

One thing is certain..........fuse 10 also powers the climate control system. Do a quick check to be sure this fuse is good.

If you don't get any other good responses, I'll post later tonight after I review the climate control manual and verify the path.

[whunter]

Originally Posted by LNGfish

1982 300SD

TY for Reading.

This is the 30 amp fuse that is for the Fan Blower and the coil for the Clutch Coil on the compressor. It might power other things.

This fuse holder was removed out of the factory box a few years ago and I used an External 50A fuse holder and down graded to a 30A fuse for the sytem. So it is at factore specs.

This has been fine for a couple of years.

Compressor coil not engaging, energizing. No voltage at coil.

Runs ok if voltage is jumped to coil.

Today, using a voltmeter I noticed voltage drops from 14 V to 0.0 V when ever there is a load put on this circuit. ie "simply installing the fuse", with sytem on max cold, the voltage drops off to zero. There is no big sparking so it is not load related, more of a power supply problem.

I need to know where this voltage/current originates from. I'm assuming the Push Buttons, but I;'m not sure. I see the wire run down out of the bottom of the fuse box.

Please give me an idea of how to get to where this wire goes so I can check for a loose connection, hoping.

I have never removed the AC brain, or ever seen the push buttons assembly, so some brief help would be appreciated to work in this area so I don't mess up the wood.

Thanks for any help.

Anybody have Roys phone number or email addy?

Steve

http://www.peachparts.com/Wikka/W123ClimateControl

Climate Control:

300sd climate control
http://www.ebay.com

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Here is my contact info.

[pmckechnie]

Again, this is for my 84 500SEL. The compressor gets it's power from the Compressor Time Delay Relay in the fuse box. The relay is energized by the Push button unit to the Evaporator Temperature Regulator to the Compressor Low Pressure cut-out Switch to the Compressor Time Delay Relay.
The relay is in the fuse box
The Evaporator Temp Reg is in the Heat/AC box very close to the gas peddle.
The Compressor Low Pressure Sw is at the Drier in in the engine compartment just behind the left headlight.
The best place to check first is at the low pressure sw on the BU/GN wire. It should have power with the compressor on. If it is good there then the relay is probably bad. If not, then step back toward the Push Button unit. The evap temp regulator (switch) went bad on my car once.

On the Ign switch problem, the switch has a plug on the back that is very hard to disconnect sometimes. If you try to unplug it, be careful that the retainer on the back of the plug doesn't come off and let all the wires fall out.

Paul

[LNGfish]

Making Progress:

I removed the Cluster and noticed that if I giggle the BIG Electrical plug I can get the power to fuse 11 to drop off and if wiggle more power comes back up.

I called Roy and he said problem is Ign. Switch, not connection of plug to switch.

So this confirms I need a new switch. Making progress.

Still now sure why compressor is not running and I think Ign. Switch needs to be replaced as Roy say the harnesses rarely go bad.

THANKS ROY!

[LNGfish]

Paul,

Thanks for this valuable information. Seems I have 2 problems at one time, weird. The main problem being the Ign. Switch being bad. Let me do a little more TS with the IGN Switch plug giggled so I keep power up on the system.

I will take some notes and get back to you on what I have.

brb

[LNGfish]

Brian,

Fuse 10 looks good. Dashboard stuff operating ok when I giggle the Ignition Plug. I Know I need that minimum.

Paul,

The switch on the receiver is closed. No voltage on either side with sytem on and fan inside running.

Brian,

Thanks for looking this up when you get the time. Much appreciated.

I will go over some more later and check voltages where I need to check them but my main goal now is to get a new ignition swith installed.

Roy is going to send me directions to remove assembly as too hard to work in in place with the 3 screws. Plus I need to order a switch.

Roy says put key in position "1" to pull off the plug.

I guess I have to remove the Tumber too which I have done in the past.

I made some headway today, thanks ALL!

Steve

[LNGfish]

I checked voltage at swith by gas pedal, and voltage on both terminals, so switch closed as I think it should be. Need to now read threads posted by Roy.

[whunter]

Here is the ignition switch data
Ignition Cylinder Tumbler replacement; mixed diesel/gas

Note: I said position #2 on the key, to remove the wire connector from the ignition switch.

You are better served replacing the steering lock assembly, they have equal wear, and it will usually be the next failure.
This is why it is sold as an assembly.


.

[LNGfish]

Brian,

I pretty much described where voltage exist above. Let me list again.

1. Switch on top of receiver closed, no voltage on either side.

2. Voltage on both side of switch by gas pedal.

I have no labels for any of the relays in the fuse box and no spares. I'm not sure relay is bad but it could be. I see when I remove them underneath I saw one with a "B" labeled on where it is plugged in. Weird they are not labeled.

Sort of lost now so I quit for the day.

Thanks

Will read this ling later on tonite. Need to take a break for now.

[whunter]

Steering Lock - With Ignition Switch & Vacuum Valve
MB# 126 462 07 30
Pelican Parts - Automotive Parts and Accessories - Porsche & BMW

Ignition Switch With Protective Covering (7 Pin Connectors)
MB# 202 545 01 04
Pelican Parts - Automotive Parts and Accessories - Porsche & BMW


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