Warm-up regulator W123 230 E: which suffix number fits? (M102)
Owners of the W123's M102 four-cylinders regularly run into the same problem: the warm-up regulator has been identified as the cause – but which of the regulators on offer is the right one? Over the production run, Mercedes fitted three versions, and they are not interchangeable with each other. This guide sorts out the suffix numbers and shows which models the regulator explicitly not fits. For how to recognize a defective regulator in general, see the guide Warm-up regulator defective – symptoms and testing.
Bosch warm-up regulator 0438140065 for the M102 – completely disassembled, rebuilt with a new diaphragm and new heating resistor, and set up on the test bench to Bosch specification.
Symptoms: defective regulator or wrong suffix number?
Using a heated bimetal element, the warm-up regulator lowers the control pressure while the engine is cold and raises it again as operating temperature increases. If the regulator is wrong – because it's defective or because the wrong version was fitted – the mixture enrichment won't be right precisely during this phase.
| Symptom | Likely cause |
|---|---|
| Engine judders, surges or dies in the first few minutes, runs cleanly once at operating temperature | Warm-up regulator defective – diaphragm or heating resistor |
| After replacement with a used part, cold-running behavior is worse than before | Wrong suffix number fitted (-097 or -100 instead of -065) |
| Cold running permanently too rich, high consumption, sooty spark plugs | Control pressure too low – have the regulator checked |
| Engine starts poorly when cold up, extended cranking during the start itself | More likely cold start valve – it only operates at start-up |
| Poor starting only after the car has stood for a longer time, no problem after a short stop | More likely fuel accumulator |
Causes: why three variants – and why does the regulator fail?
The M102 was used in the W123 from 4/1980 to 12/1985, and in the G-Model from 4/1982. Over this production run, three regulator versions were fitted, each with its own Mercedes part number: -065 (102 070 01 62 or 000 070 20 62), -097 (102 070 02 62) and -100 (102 070 03 62). Visually they look alike – a regulator with the wrong suffix number will still run, just with the wrong pressure curve.
After decades, failure always affects the same components: the diaphragm ages and starts leaking, the heating resistor for the bimetal burns out, and seals harden. Nothing shows on the outside of the regulator – the control-pressure measurement is what counts.
Check it yourself: 4 steps, starting with the cheapest
- Read off the number (free): The Bosch number is stamped on the installed regulator. If it ends in -065 or reads 0438140146, our regulator is the right one. Suffix numbers -097 or -100 are different versions.
- Match engine and model year: Our version covers the M102.980 in the W123 (4/1980–12/1985) and the M102.981 in the W460 230 GE (4/1982–8/1985). From 9/1985, the 230 GE runs KE-Jetronic – no warm-up regulator is fitted there at all.
- Visual and voltage check: Is the regulator damp with fuel on the outside? With the engine running, is there voltage at the disconnected connector? Without power, the bimetal doesn't heat and the regulator stays in cold mode.
- Measure the control pressure: The only reliable diagnosis. With a test gauge between the fuel distributor and the warm-up regulator, the control pressure is checked cold and warm against the Bosch target values – this is how we work at our test bench too.
Solution: remanufactured Bosch 0438140065
New parts are no longer available for these regulators, and an unrestored used part has the same aged diaphragm as your old one. Our version is remanufactured: completely disassembled, cleaned in an ultrasonic bath, new diaphragm, new heating resistor, springs checked and replaced if needed, all seals renewed, and set up on the test bench to Bosch specification – pressure values documented, new copper sealing rings included. 499,00 € each, four in stock.
Bosch 0438140065 – suffix number -065
W123 230 E / CE / TE (M102.980) · W460 230 GE (M102.981)
499,00 € · remanufactured
View offer →
Suffix number -100
Different M102 version – only if this number is on your old part
499,00 € · remanufactured
View offer →For suffix number -100 there is also a tested genuine used part for 49,99 € – without refurbishment, but affordable. You'll find all versions and current stock in the category Warm-up regulators, more W123 parts in the W123 Collection.
Number on the old part illegible?
Send us the chassis number and model year, or a photo of your installed regulator – we'll check for free which suffix number your vehicle needs. Bosch 0438140065, remanufactured, 499,00 € · 4 in stock.
Check fitment for free →Compatible vehicles
| Model series | Models | Engine | Production period |
|---|---|---|---|
| Mercedes W123 / C123 / S123 | 230 E Sedan (123.223), 230 CE Coupe (123.243), 230 TE Estate (123.283) | M102.980 · 2,3 l · 100 kW / 136 PS | 4/1980 – 12/1985 |
| Mercedes W460 G-Model | 230 GE, identical to the Puch G 230 GE | M102.981 · 2,3 l · 92 kW / 125 PS | 4/1982 – 8/1985 |
Explicitly does not fit: Vehicles with KE-Jetronic (W124 230 E from 1985, W460 230 GE from 9/1985 – there, an electro-hydraulic actuator handles this task), the M110 six-cylinders (280 E, 280 CE, 280 SE, 280 SEL, 280 SL, 280 SLC, 280 GE – there it's 0438140057, 0438140067 or 0438140103), the V8 models 380 / 450 / 500 / 560, the carburetor models 230, 230 C and 230 T with M115, and all diesels.
FAQ
Which warm-up regulator fits the W123 230 E?
Three different warm-up regulators were fitted to the M102 over its production run. Our version is the suffix number -065 (Bosch 0438140065, Mercedes 102 070 01 62 or 000 070 20 62). Suffix numbers -097 (102 070 02 62) and -100 (102 070 03 62) are different versions. The number on your installed regulator is always decisive.
Is 0438140146 the same as 0438140065?
Yes. The Bosch replacement number 0438140146 is identical to 0438140065 and directly interchangeable. If this number is on your old part, our regulator fits.
Does the regulator also fit the 230 GE?
Yes, in the W460 230 GE from 4/1982 to 8/1985 with the M102.981 engine, and identically in the Puch G 230 GE. From 9/1985, the 230 GE has KE-Jetronic – no warm-up regulator is fitted there.
Why doesn't my W124 230 E have a warm-up regulator?
Because it has KE-Jetronic. There, an electro-hydraulic actuator handles mixture adjustment during cold running, and no warm-up regulator exists. This applies to the W124 230 E from 1985 as well as the W460 230 GE from 9/1985.
What's included with a remanufactured regulator?
Complete disassembly, cleaning in an ultrasonic bath, new diaphragm, new heating resistor, springs checked and replaced if needed, all seals renewed, and adjustment on the test bench to Bosch specification with a record of the pressure values. New copper sealing rings are included.
KFZTeile-Thot is a specialist workshop for tested and refurbished Mercedes parts with our own test benches, specializing in Mercedes classic cars and K-Jetronic components – over 1,000 eBay reviews (almost all positive). Not sure about the suffix number? Call us: 0179 8991069 (Mon–Fri 8 am–6 pm) or use the contact form. Related guides: Warm-up regulator defective – symptoms and testing and Cold start valve: testing and replacing.