Mercedes A/C Relay A0025451205 4-Cylinder W124 W201 190E G-Class 12V Tested
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Genuine Mercedes-Benz A/C relay A 002 545 12 05, 4-cylinder version, 12 V, for W124, W201 and G-Class.
Genuine Mercedes part (Kostal) · Tested for function · Fits W124, W201 & G-Class (4-cylinder)
✓ Function tested
Condition of this part
Used genuine part, tested and functional. The housing shows light usage scratches and storage marks, the plug contacts a slight tarnish – no bent or missing pins, no cracks.
Function and location
More than a simple switching relay: this A/C relay is a small control unit for the air conditioning system. It switches the magnetic clutch of the A/C compressor while monitoring drive belt slip via a speed comparison between the compressor and engine (belt and compressor protection), switches off the compressor if the coolant temperature is too high or under full load/kickdown, and delays switch-on after the engine starts.
It is installed in the relay/electronics compartment in the engine bay, behind the starter battery, next to the fuel pump relay.
How can you tell an A/C relay is defective?
- The A/C compressor no longer engages even though the refrigerant and electrics are fine
- Belt and compressor protection via speed monitoring stops working
- No more compressor shutoff at excessive coolant temperature or under full load/kickdown
- The switch-on delay after engine start no longer occurs
Compatible vehicles
Mercedes W201 (approx. 1985–1993):
- 190 E 1.8
- 190 E 2.0
- 190 E 2.3
- 190 D
Mercedes W124 (approx. 1985–1992):
- 200, 200 E, 200 T, 200 TE, 200 D, 200 TD
- 230 E, 230 E Cat, 230 CE, 230 CE Cat, 230 TE, 230 TE Cat
Mercedes G-Class:
- 200 GE, 230 G, 230 GE, 240 GD
Genuine/OEM number of this relay: A 002 545 12 05, 4-cylinder version marked "4 Zyl. Kli", index level [09], made by Kostal. The six-cylinder version carries the number A 002 545 13 05, the V8 version A 002 545 18 05. For later M111 models such as the E 200 and E 220, 003 545 54 05 and others apply.
⚠ Important: compare the part number before buying
The "4 Zylinder" marking on the relay is decisive. It identifies the correct version – relays with other markings are intended for other engine variants and are not interchangeable.
Does not fit:
- Mercedes W201: E 2.6, 2.6, D 2.5, Turbo D 2.5
- 6-cylinder versions (there A 002 545 13 05)
- V8 versions (there A 002 545 18 05)
- Later M111 models such as the E 200 and E 220 (there 003 545 54 05, among others)
Does this part fit your car? Send us the VIN (chassis number) and model year – we'll check it for free: 0179 8991069 (Mon–Fri 8 am–6 pm) or via our contact form.
FAQ
How can I identify the correct version?
By the marking on the relay housing: this relay carries the designation "4 Zyl. Kli" for the 4-cylinder version. Other markings denote 6-cylinder or V8 engines and are not interchangeable.
Is the relay tested?
Yes – this is a used genuine part that has been tested for function and works.
What does it mean if the A/C compressor no longer engages?
According to the vehicle system, this is the typical failure pattern of a defective A/C relay, when the refrigerant and electrics are otherwise fine.
Related categories: Relays · W201 · W124
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