First off we love out euro 300d thanks to sixto!!! I need help with the climate control. According to the papers its been changed 3 times in the 90s (unit) so I wanna start with fuses etc. Oh it blows hot air when driving and the fan kicked on for a second while driving home.

Also the glow plug light is short. You have to cycle it a few time and the engine starts right up. Glow plug relay? Also were is it located. I have access to my other 300d I can use for donor parts tell I can purchase parts.

Also I got 44.5 mpg on the way home.

The GP light is an idot light. The light goes off after 10 seconds or so, but the relay and GPs stay on for a lot longer(about 45 second). If you leave the key in the glow position you'll eventually here the relay kick off.

In the summer you should only have to wait for the light to get the car to start. After the light goes out it should start right up. But if you have to cycle it several times in warm weather to get it to start then you've got a GP system problem or a compression problem.

Even in the winter a tight engine will still start with only one glow cycle, but in a more tired engine you may have to cycle through a couple times to get it to start.

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Ok I waited 45 seconds like you said and she starts right up. She sat all night I went out waited 45 sec and it started right up. The light lasts about 5 seconds any suggestions to fix that?

The glow relay is on the driver side inner fender. It's a black box about 4" x 5" x 1.5". If your car has ABS, it's behind the ABS pump.

The OE glow relay will show the light for a few seconds in most conditions. An afterglow relay will show the light for a second or not at all on a hot restart. If it doesn't light for 5-10 seconds when cold, there might be a problem with the internal temp sensor, or it might use glow plug resistance(?) to gauge engine temp. Or being an early Euro, it might rely on an external temp sensor. How many pins are there on the small glow relay connector?

Cabin heat is to be expected from an iffy ACC PBU. Does the heat persist if you set the PBU to off or 0? Do you hear solenoids click near the glove box when you select different modes? Multiple PBU replacements could be someone trying to figure out a problem with the Klima relay.

Consider purchasing a copy of Haynes W124 manual. It's not a factory service manual (FSM) but it has basic info on UK and non-US equipment.

http://www.amazon.com/Mercedes-Service-Repair-Manual-Manuals/dp/1859602533/ref=sr_1_1?ie=UTF8&qid=1315430774&sr=8-1

Sixto
87 300D

I will get back to you on the relay.
The climate control seems dead. I will check it again but I heard no clicking at all. Doesn't matter what button you push the window vent blows hot air. When you stop there is no heat blowing out. Sixto I still need to check fuses. I looked none are blown but look like they need replaced.
Isn't there another fuse out of the fuse box for the climate control?

There might be a separate fuse for the blower motor but for the PBU itself the fuse is in the fuse box.

If you're blowing fuses, you might have a bad aspirator motor or monovalve.

Sixto
87 300D

Ok changed the fuse no luck and no clicks when I push the buttons.

Ok so were do I start to fix the climate control? Change out the button assembly?

Get yourself a FSM and study the ACC wiring and vacuum control diagram. Make sure you're getting power to the PBU and solenoid bank.

Sixto
87 300D

Still learning sixto:-) fpu? Solenoid bank?
Did some google search. I can not find strip fuse on the driver side strut tower. It also said to check 7 and 12 fuse both good. Pulled the button unit pulled apart and checked the board and sprayed with wd40. Still nothing. Also sprayed wd40 on the fuse box. Pulled the glovebox inspected that bar that has hoses on it. It looks really clean. No clicking in that area when a button is hit. Im convinced there is no power going to the unit.

Does anyone have a wire diagram?[/LIST]

Ok I swapped the button panel and got the fan to work. I don't think the ac is kicking on but I didn't have much time to play with it. The middle vents aren't blowing air.

Is there a link so I can fix my button panel?

124 and late 126 PBUs don't respond well to resoldering IMO. Get a new one ($$$) or a known good used one. There's no DIY for rebuilding a PBU. More likely your problem is dead vent selection vacuum actuators or pods. Remember what I said about manual AC being a desired Euro feature? You're about to learn why. When the PBU is out, look into the dash towards the glove box. You'll see a long box with colored dots and lots of vacuum hoses. That's the solenoid bank. It distributes vacuum (thinking of vacuum as a commodity) to actuators that open and close flaps in the airbox to send air to the specific registers. A common problem is loss of source vacuum, a more common problem is dead acfuators. Replacing the actuators that control recirculation and dash center vents requires removing the dash. There are several DIYs on that topic, one by me. The DIYs assume you've confirmed bad actuators. So first get your hands on a vacuum circuit diagram and test the actuators from the solenoid bank connections. You should also check electrical signals from the PBU to the solenoid bank but that's rarely a problem.

Sixto
87 300D

Ok I have a new well refurbished button thing coming for 45. Im waiting to see how much for the valve thing is. I don't think the ac is kicking on what controls that? Same? ? What fuses for the ac same?

There's a looong chain from the PBU to the compressor, at least in US spec 300Ds. The first thing to check is for +12V at one of the wires connected to the low pressure switch, the one without pigtails, on the receiver/drier. With the engine running, set the PBU to defrost and check for +12V at one of the pins. Also check for continuity across the low pressure switch. If you get +12V at one of the wires, the PBU is telling the compressor to engage. If you don't get +12V at either wire, the problem is in the cabin. Let's start with this then figure out how to proceed.

Sixto
87 300D

Ok well had my friend look at the ac. He touched those 2 wires together and the ac compressor kicked on. Then we pressed the nipple on the ac line and it barely hissed. He thinks its empty.