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crookednose 09-02-2001 03:58 AM

Relay questions
 
My car is 1987 190 Euro. There is no relay in the slot (R4) where my OVP relay is supposed to be. Am I suposed to have one, since my car is not F/I? The relay(001 542 59 15) in slot (R3) which is supposed to be an A/C relay does not effect the A/C. I removed this relay and the A/C works normally. There is one relay(001 542 95 19) in the additional relay holder(position C) that has some burn marks on the pins and some melted insulation. The vaccum operated height adjustment on my headlights was not working but after pulling and reseating all relays it started working.

Benzmac 09-02-2001 09:49 PM

The overvoltage relay, fuel pump relay, and Klima relay are all behind the area of the battery.

The other relays that are in the fuse box are for other high draw electrical functions.

crookednose 09-03-2001 12:41 AM

I was relying on information from my Haynes manual which shows the location and name of relays and fuses. This manual covers only US models but the pictures of the relays which show the number of live pins in the relay socket, correspond with my cars set up. The only relay behind my battery is a bosch relay. When this relay is disconnected my A/C compressor does engage. The A/C system was not installed at the factory.

stevebfl 09-03-2001 09:22 AM

If you have a carb model and no ABS then you probably don't have a OVP relay and I have never seen an after installation of A/C done with anything but simple 4 or 5 pin relays.

crookednose 09-03-2001 05:14 PM

I was originally trying to find out why my vacuum operated headlight adjustments was not working and after reseating all the relays it started working. This is when the question of relay operation came up. The relay behind my battery is a simple 5 pin(female terminal clips on to the relay's male pins) relay with a 30 amp fuse, Bosch p/n (0 332 019 150). I know this controls my A/C compressor. I am trying to find what the relay(001 542 59 15) in slot (R3) which according to my haynes manual is an A/C relay, really controls. I am attempting to troubleshoot an A/C temperature slider control that does not change the temperature of the air coming out of the vents, it is always very cold. In addition, I am trying to find out what the single relay(001 542 95 19) in position C in the additional relay compartment controls. In my haynes manual it says postion C is not used. I have a relay in this position and the socket connected to it is live and has some slight burn marks and melted insulation.

stevebfl 09-03-2001 05:26 PM

Your car no more resembles the uS model than it does a 240D. The US only gets the fully optioned car including automatic A/C. Since your car didn't come with any A/C you will not find a wiring diagram for it.

You will have to diagnose it by function. Are you saying that you want to have the compressor cycle more (at a higher temp) or are you wanting to mix heat with A/C? This will probably have to be done manually.

crookednose 09-03-2001 05:46 PM

The A/C system was added at the dealer when the car was new before it put on the showroom floor. I know both previous owners of the car. The temperature of the air air coming form the dash vents is always the same freezing temp. In the daytime Kuwait heat this freezing air is perfect. However at night the A/C will freeze you out, but you need some cooling air to be conmfortable and I don't want to cycle the compressor off and on to control temp. The temperature slider control has no effect on this temp. Is the temperatue slider supposed to cycle the compressor off/on to control temp or is the slider control supposed to control temp a different way.

stevebfl 09-03-2001 05:54 PM

Without automatic A/C there is really only volume of air control. The temp controll will only affect the cycling rate. It will increase duct temp but it will still be A/C. Modern systems blend heat and A/C to get warmer temps.

You will have to find a way to control the mix with a combination of duct control and heat. Closing the center duct should reduce the temp. If you add some heat, it should go to the outer vents. I am not familiar with your controls so I am guessing.

crookednose 09-03-2001 06:29 PM

Thanks for you replys. The temperature slider control has Min and Max markings on the ends of the control, with blue marks in between that increase in width as they get toward the Max end. There is a small snowflake on the Min end and a large snowflake on the Max. I believe the temperature slider control should function somewhat like the thumbwheel temp degree control on automatic systems. I don't believe Mercedes would mark this slider control in such a meticulous manner if did not control something, it may be possible that the dealer did a shortcut installation and did not enable this slider control to function properly. All of the repair shops here are well below American standards and we all have many horror stories, that is why I use this forum for answers to simple questions that could be answered in minutes if my car was in the US. I have used the search many times on this forum and have always found an answer or at least a hint in the right direction.

JimSmith 09-03-2001 11:08 PM

crookednose,

I have a Euro 190E 2.3-16 with a factory installed manual a/c system that has a horizontal slider control for the temperature of the air in the car. This slider is not a control for the temperature of the air coming out of the vents. It controls the interior temperature of the car, and it is not a calibrated scale. The point of the markings is to make it intuitive to the person wanting to have the a/c cool him or her off more or less which way to push the lever. The lever merely sets the compressor duty cycle, and I do not even think there is a feedback sensor in the system to make the cycling a result of the temperature changes in the car's interior.

If the temperature in the car is too cold, you can turn the fan down to 2 (I am not sure the a/c works on a fan setting of 1) and turn the slider control to the shorter blue marks. This will turn the a/c compressor cycle from more time per hour "on" to less time per hour "on" and push a reduced volume of cooled air into the car's interior.

In my car I can also turn the heat on at the same time, and in New England, when the humidity is high and the windows are fogging up in a rain storm this really helps dry out the air and clear the windows. However, if it is hot outside, and the heat is turned on at the same time as the a/c, the dehumidifying characteristics continue, but the compressor will stay on longer but the cooling capacity of the system will be reduced. I actually think the heating system of the car can overwhelm the a/c system's capacity to remove heat.

By the way, the relays on my car are behind a black plastic shield behind the battery (on the passenger side of the space in front of the firewall). The shield is held in place by a rubber gasket that seals water and other stuff from the windshield area out of the protected space behind the battery where these and other relays are located across the width of the car. In the area of the OVP relay there are two relays located one in front of the other, with the OVP relay with its clear plastic cover and fuse on top, next to them, closer to the center of the car. Further inboard is the electronic ignition control module. I would find it odd that Mercedes would have a totally different layout for components in your model. The a/c relay is a little black box and has the word "KLIMA" on it, along with things like "12V" and "4 Zyl" in white letters. The other relay is an identical size black box and has "4 Zyl. 7100min" on it and I believe that is the fuel pump relay. The OVP relay is silver and is significantly smaller than the other two.

I hope this clarifies somethings for you.

Jim

crookednose 09-04-2001 03:13 AM

Jim, thanks for your reply. As I stated before the only relay behind my battery is the Bosch 5 pin relay. it is bolted to the firewall and has wires that go a ternminal block, insted of being plugged in directly. When disconnected the compressor will not engage. The one parts guy at the dealer that I can trust looked at the relay, and told me that it functioned as the Klima relay. He directed me to the bosch deaker where I bought the relay for about $2. My central electronics setup is exactly the same as the pictures in my US Haynes manual, but the spot for the OVP is empty. The only relay with 4 ZYL printed on it is on my central electronics unit, it is the largest of the 3 relays on the unit. My car has a mechanical fuel pump. It is good to talk to someone who has the manual A/C setup. The horizontal slider control on my car has no effect on anything, I have repeatedly checked this. I wish I had a digital camera.


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