Warm-up regulator – sale, repair & purchase (Bosch K-Jetronic)
The warm-up regulator (control-pressure regulator) regulates, in the Bosch K-Jetronic the control pressure and therefore the fuel-air mixture: when the engine is cold, it enriches the mixture; as the temperature rises, it leans it out to operating values. If the diaphragm ages or the internals become gummed up, the engine runs poorly – especially during the warm-up phase. Since Bosch no longer supplies new warm-up regulators, overhaul and tested used parts are the way forward today. With us you get both – and we pay you money for defective regulators.
Buy an overhauled warm-up regulator
Tested Bosch warm-up regulators from stock – ready to ship, with invoice. Stock changes constantly; we're happy to check your part number.
View selectionHave your regulator repaired
Complete overhaul: new diaphragm & seals, new heating element if needed, housing refurbished like new, function test. Return shipping included (DE), 12 months statutory warranty. Your genuine part is retained.
Book repairSell your defective regulator
We buy every complete defective Bosch warm-up regulator – simply by e-mail or phone.
To the buy-backHow can you tell a warm-up regulator is defective?
Typical symptoms of a defective warm-up regulator are:
- Poor cold start or stalling shortly after starting
- Jerking, surging or rough idle during the warm-up phase (first 5–10 minutes)
- Poor throttle response and noticeable lack of power
- Noticeably increased fuel consumption (mixture permanently too rich)
- Problems with warm starting
- During testing: incorrect control pressure cold and/or warm
Certainty comes from measuring the control pressure with a pressure gauge between the fuel distributor and the warm-up regulator – the values must match the Bosch target values for your regulator's part number. Common internal causes: aged or cracked diaphragm, clogged screens, corroded internals, defective heating coil.
Repair & overhaul – how it works
We overhaul both types completely: warm-up regulators without vacuum and with vacuum (vacuum connection) – on vacuum regulators, the vacuum diaphragm is always replaced as well.
- Book repair – directly online in the shop or by phone. You will receive the return address with your order confirmation.
- Remove & send in your regulator – two fuel lines, connector, two screws. Well packaged as a parcel to us.
- Overhaul with us – disassembly, cleaning and refurbishment of the surface (the housing looks like new again), new diaphragm and seals (brand-name repair kit), new vacuum diaphragm on vacuum regulators, new heating element if necessary – then reassembly and function test. Processing usually takes a few business days.
- Return shipping included – install it and enjoy smooth cold running. With 12 months statutory warranty.
Buy-back: €50 for your defective warm-up regulator
Do you have a defective warm-up regulator left over – from a donor vehicle, a parts box, or after a conversion? We pay a flat €50 per piece for every complete Bosch warm-up regulator (0 438 140 …), regardless of condition. Here's how it works:
- Photo and part number by e-mail to thot.kfzteile@gmail.com or give us a quick call: 0179 8991069
- You will immediately receive confirmation and our shipping address
- Payment by bank transfer or PayPal upon receipt
For which vehicles? All Bosch K-Jetronic
We overhaul, buy and sell all warm-up regulators with a Bosch number 0 438 140 … – regardless of vehicle make. Typical vehicles with K-Jetronic:
| Mercedes-Benz | R107/W107 (280–500 SL/SLC), W116, W123 (230 E, 280 E), W126 (280–500), 280 models with M110, V8 M116/M117, 280 GE (W460) |
|---|---|
| Porsche | 911 (2.7, SC, Carrera 3.0), 930 Turbo, 924, 928 |
| VW / Audi | Golf I GTI, Scirocco, Jetta • Audi 100/200 5-cylinder, Urquattro |
| Other | Volvo 240/260, Saab 99/900 Turbo, Ferrari 308i/Mondial, DeLorean DMC-12 and many more |
Why KFZTeile-Thot?
- Specialised in Mercedes classic cars and the Bosch K-Jetronic – parts trading and workshop practice from a single source
- Over 1,000 positive reviews from our eBay trading
- Like-new appearance included: The housing surface is refurbished with every overhaul
- Fixed price, clear service: €400 incl. return shipping, 12 months statutory warranty – no surprises
- Fast processing: Usually processed within a few business days
FAQ about the warm-up regulator
What does the warm-up regulator do in the K-Jetronic?
It regulates the control pressure acting on the fuel distributor's control plunger, thereby determining the mixture composition. When the engine is cold, it lowers the control pressure – the mixture is enriched (cold-running enrichment). As engine temperature rises, the control pressure increases and the mixture leans out to operating values. Variants with a vacuum connection additionally enrich under full load.
What are the symptoms of a defective warm-up regulator?
Poor cold start, stalling after starting, jerking and rough running during the warm-up phase, poor throttle response, increased consumption and warm-start problems. It becomes clear with a control pressure measurement: if the values deviate from the Bosch target values when cold or warm, the regulator needs replacing.
What does warm-up regulator repair cost and what's included?
€400 fixed price including return shipping within Germany and 12 months statutory warranty. Included are disassembly, cleaning, refurbishment of the housing surface (like-new appearance), new diaphragm and seals (brand-name repair kit), a new vacuum diaphragm on vacuum regulators if applicable, a new heating element if necessary, plus the function test.
Do you also overhaul warm-up regulators with vacuum (vacuum capsule)?
Yes, we fully overhaul both types – warm-up regulators without vacuum and with vacuum. On vacuum regulators, the vacuum diaphragm is always replaced as well; a defective heating element is replaced if needed.
How long does the repair take?
Usually a few business days from receipt of your regulator. We confirm the exact time frame when we receive your order.
Why repair instead of a replacement regulator?
Bosch no longer supplies new warm-up regulators. With an overhaul, your original part with the part number matching your vehicle is retained – a plus for originality and value retention. It also eliminates the core deposit and the risk of an unknown replacement part.
For which vehicles do you offer repair and buy-back?
For all Bosch warm-up regulators with part number 0 438 140 … – including Mercedes R107, W116, W123, W126, Porsche 911 SC/930/924/928, VW Golf I GTI, Audi 100/200/Urquattro, Volvo, Saab, Ferrari and DeLorean.
Does the KE-Jetronic also have a warm-up regulator?
No. With the KE-Jetronic, the electro-hydraulic actuator handles mixture adjustment – a warm-up regulator only exists on the K-Jetronic (including K-Jetronic with lambda control). If you have issues with the KE-Jetronic, feel free to contact us anyway.
How does the buy-back of defective warm-up regulators work?
Send us a photo and the part number by e-mail or phone, and you'll immediately receive confirmation and our shipping address. Upon receipt, we pay out €50 per complete regulator by bank transfer or PayPal.
Can I repair the warm-up regulator myself?
Repair kits are available, and the installation itself is doable for an experienced DIYer. But without control-pressure measuring equipment and experience, it remains guesswork: an incorrectly working regulator leads to poor running and higher consumption. That's why our overhaul always includes the function test.
Direct line
Phone: 0179 8991069 (Mon–Fri 8 am–6 pm)
E-mail: thot.kfzteile@gmail.com
Or use our contact form – we'll get back to you as soon as possible.