{"product_id":"ac-controllers-amplifiers","title":"AC Controllers\/Amplifiers","description":"\u003ch2\u003eAC Controllers\/Amplifiers \u003c\/h2\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003eOffered by MR2 Heaven in collaboration with Messerworks LLC\u003c\/p\u003e\n\u003cp\u003eAll units are built and tested prior to shipping\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003cp\u003eReplaces the beige or black AC \u003cspan\u003eamplifier under your dash that is discontinued and no longer available from Toyota.\u003c\/span\u003e\u003c\/p\u003e\n\u003ch2\u003e\u003cbr\u003e\u003c\/h2\u003e\n\u003ch2\u003eWhich unit does your car need?\u003c\/h2\u003e\n\u003cp class=\"section-lede center\"\u003eToyota fitted three different A\/C amplifiers across the SW20 run. They look alike, they are not interchangeable, and between them the terminal numbering changed completely. Five minutes with a torch settles it — and it is the one thing you must get right before you order anything on this page.\u003c\/p\u003e\n\u003col class=\"checks reveal visible\"\u003e\n\u003cli\u003e\n\u003cspan class=\"check-num\"\u003e1\u003c\/span\u003e\n\u003cdiv\u003e\n\u003ch3\u003eFind the amplifier and read its label.\u003c\/h3\u003e\n\u003cp\u003eIt is the box the \u003ccode\u003eA9\u003c\/code\u003e harness plug goes into, behind the center console under the dash. On the label is a Toyota part number beginning \u003ccode\u003e88650-\u003c\/code\u003e. That number is the answer — not the year, not the engine.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cspan class=\"check-num\"\u003e2\u003c\/span\u003e\n\u003cdiv\u003e\n\u003ch3\u003eNo label, or unreadable? Count the wires.\u003c\/h3\u003e\n\u003cp\u003eCount the populated cavities in the A9 plug. \u003cstrong\u003e14 populated is the \u003ccode\u003e-17120\u003c\/code\u003e family.\u003c\/strong\u003e \u003cstrong\u003e16 is the \u003ccode\u003e-17130\u003c\/code\u003e family.\u003c\/strong\u003e The two extra wires on the later car are a brown \u003ccode\u003eBR\u003c\/code\u003e — the amplifier's own output to the engine ECU — and a brown\/white \u003ccode\u003eBR-W\u003c\/code\u003e strap.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cspan class=\"check-num\"\u003e3\u003c\/span\u003e\n\u003cdiv\u003e\n\u003ch3\u003eUse the build date as a cross-check, never as proof.\u003c\/h3\u003e\n\u003cp\u003eUS 1991 is almost always \u003ccode\u003e-17120\u003c\/code\u003e. US 1993–95 is \u003ccode\u003e-17130\u003c\/code\u003e. \u003cstrong\u003eA US 1992 car has to be read off the label\u003c\/strong\u003e — the changeover happened in December 1991, which falls inside that model year. Any car built from December 1991 onward, in any market, is \u003ccode\u003e-17130\u003c\/code\u003e.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cspan class=\"check-num\"\u003e4\u003c\/span\u003e\n\u003cdiv\u003e\n\u003ch3\u003eHas the engine been swapped?\u003c\/h3\u003e\n\u003cp\u003eThen you want the \u003cstrong\u003eSwap Edition\u003c\/strong\u003e — but only if the car started life with a \u003ccode\u003e-17120\u003c\/code\u003e. A swapped car that came with a \u003ccode\u003e-17130\u003c\/code\u003e should wait for Unit B, whose firmware can switch the extra outputs off.\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003csection class=\"band\" id=\"fits\"\u003e\n\u003cdiv class=\"wrap narrow\"\u003e\n\u003ch2\u003eSwap Edition — make sure this is actually your car\u003c\/h2\u003e\n\u003cp class=\"section-lede\"\u003eThe Swap Edition is built for one specific situation. Check these four things before you spend anything; if any of them is not you, the \u003ca href=\"https:\/\/messerworksllc.com\/sw20-ac-controller#lineup\"\u003elineup\u003c\/a\u003e has the unit that is.\u003c\/p\u003e\n\u003cul class=\"fitment\"\u003e\n\u003cli\u003e\n\u003cspan class=\"fit-key\"\u003eReplaces\u003c\/span\u003e\u003cspan class=\"fit-val\"\u003eAmplifier part number \u003ccode\u003e88650-17120\u003c\/code\u003e — the beige unit on early cars. That part number is what the Swap Edition was designed against. A \u003ccode\u003e-17130\u003c\/code\u003e car needs \u003ca href=\"https:\/\/messerworksllc.com\/sw20-ac-controller#lineup\"\u003eUnit B\u003c\/a\u003e.\u003c\/span\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cspan class=\"fit-key\"\u003eEngine\u003c\/span\u003e\u003cspan class=\"fit-val\"\u003eAn engine swap — 2GR-FE or similar. The A\/C circuit itself is stock MR2, so what matters isn't which engine, it's that the original engine-management side of the amplifier's job is gone.\u003c\/span\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cspan class=\"fit-key\"\u003eTransmission\u003c\/span\u003e\u003cspan class=\"fit-val\"\u003eManual. Automatics used an extra amplifier terminal that isn't part of this build — a stock automatic is covered by \u003ca href=\"https:\/\/messerworksllc.com\/sw20-ac-controller#lineup\"\u003eUnit A\u003c\/a\u003e.\u003c\/span\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cspan class=\"fit-key\"\u003eECU signal\u003c\/span\u003e\u003cspan class=\"fit-val\"\u003eYour swap ECU takes its A\/C input as \u003cstrong\u003e+12 V\u003c\/strong\u003e from the same wire that engages the clutch. That's the factory \u003ccode\u003eB-W\u003c\/code\u003e signal path, and it's how this controller hands your ECU the idle-up request. If your ECU expects a ground instead, talk to me before ordering.\u003c\/span\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3 class=\"sub-head\"\u003eThen confirm the amplifier is really the fault\u003c\/h3\u003e\n\u003cp class=\"section-lede\"\u003eThis takes ten minutes and tells you whether you need this part or something cheaper.\u003c\/p\u003e\n\u003col class=\"checks\"\u003e\n\u003cli\u003e\n\u003cspan class=\"check-num\"\u003e1\u003c\/span\u003e\n\u003cdiv\u003e\n\u003ch3\u003eYour refrigerant charge is good.\u003c\/h3\u003e\n\u003cp\u003eA low system won't engage the clutch no matter what controls it — the factory pressure switch cuts it off. Check the charge first.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cspan class=\"check-num\"\u003e2\u003c\/span\u003e\n\u003cdiv\u003e\n\u003ch3\u003eGrounding the \u003ccode\u003eL-O\u003c\/code\u003e wire engages the clutch.\u003c\/h3\u003e\n\u003cp\u003eAt the amplifier plug, jump the blue\/orange wire to ground with the engine running. If the compressor kicks in and you get cold air, your compressor, clutch, relay, and refrigerant are all fine — the amplifier is the failure.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cspan class=\"check-num\"\u003e3\u003c\/span\u003e\n\u003cdiv\u003e\n\u003ch3\u003eYour A\/C button does nothing.\u003c\/h3\u003e\n\u003cp\u003e12 V shows up on the pink wire when you press it, but the clutch never engages. That's the amplifier failing to close the loop.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003c\/ol\u003e\n\u003cdiv class=\"callout callout-warn\"\u003e\n\u003cstrong\u003eIf grounding L-O does nothing, stop.\u003c\/strong\u003e Your problem is upstream — relay, fuse, pressure switch, compressor, or charge — and this controller will not fix it. The full diagnostic checklist ships with every order, and if you're not sure what you're seeing, email me before you buy and I'll talk it through with you.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/section\u003e\n\u003csection class=\"band band-alt\"\u003e\n\u003cdiv class=\"wrap\"\u003e\n\u003ch2\u003e\u003cbr\u003e\u003c\/h2\u003e\n\u003ch2\u003eWhat it actually does\u003c\/h2\u003e\n\u003cp class=\"section-lede center\"\u003eThe factory amplifier had five jobs. This reproduces all five, from the same wires, at the same plug.\u003c\/p\u003e\n\u003cdiv class=\"feature-grid reveal visible\"\u003e\n\u003carticle class=\"feature\"\u003e\n\u003ch3\u003eClutch control\u003c\/h3\u003e\n\u003cp\u003eA logic-level MOSFET grounds \u003ccode\u003eL-O\u003c\/code\u003e to energize the A15 clutch relay — exactly what the OEM unit did, with no mechanical contacts to burn.\u003c\/p\u003e\n\u003c\/article\u003e\n\u003carticle class=\"feature\"\u003e\n\u003ch3\u003eFreeze protection\u003c\/h3\u003e\n\u003cp\u003eReads your factory evaporator thermistor and cycles the compressor with proper hysteresis plus minimum on\/off timing. No short-cycling, no iced core.\u003c\/p\u003e\n\u003c\/article\u003e\n\u003carticle class=\"feature\"\u003e\n\u003ch3\u003eEngine-run detection\u003c\/h3\u003e\n\u003cp\u003eSenses alternator charging voltage with hysteresis and a dip-grace timer, so the compressor's own engagement sag doesn't drop it out. Key-on with the engine off does nothing, same as stock.\u003c\/p\u003e\n\u003c\/article\u003e\n\u003carticle class=\"feature\"\u003e\n\u003ch3\u003eRadiator fans, both stages\u003c\/h3\u003e\n\u003cp\u003eAn on-board relay sources 12 V to the fan enable circuit, and a second output holds the motors in series for LOW — releasing to parallel HIGH above ~90 °C. The factory behavior most replacements skip entirely.\u003c\/p\u003e\n\u003c\/article\u003e\n\u003carticle class=\"feature\"\u003e\n\u003ch3\u003ePressure safety left in hardware\u003c\/h3\u003e\n\u003cp\u003eYour A13 dual pressure switch still gates the relay's power feed. High or low refrigerant pressure cuts the compressor whatever the software thinks. That circuit is untouched.\u003c\/p\u003e\n\u003c\/article\u003e\n\u003carticle class=\"feature\"\u003e\n\u003ch3\u003eIdle-up signal\u003c\/h3\u003e\n\u003cp\u003eThe \u003ccode\u003eB-W\u003c\/code\u003e wire — 12 V only while the clutch relay is closed — is the factory signal path to the ECU's A\/C input. Tap it and your ECU raises idle under compressor load.\u003c\/p\u003e\n\u003c\/article\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/section\u003e\n\u003csection class=\"band\"\u003e\n\u003cdiv class=\"wrap\"\u003e\n\u003cdiv class=\"split\"\u003e\n\u003cdiv\u003e\n\u003ch2\u003eWhy swapped cars first\u003c\/h2\u003e\n\u003cp\u003eWhen you swap an engine into an SW20, the A\/C amplifier loses half its job. The vacuum idle-up actuator it used to drive is gone with the old engine, and the igniter signal it watched for the high-RPM cutout belongs to an ignition system that isn't in the car anymore.\u003c\/p\u003e\n\u003cp\u003eA swap ECU handles those itself. It just needs to be told the compressor is engaging — and it wants that as +12 V on the same wire that closes the clutch relay. So the controller's job gets simpler and cleaner, and everything left is A\/C circuitry that's still pure MR2.\u003c\/p\u003e\n\u003cul class=\"tick-list\"\u003e\n\u003cli\u003e\n\u003cstrong\u003eTape off the vacuum idle-up wire.\u003c\/strong\u003e There's no actuator on the other end of it anymore.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTap B-W to your swap ECU's A\/C input.\u003c\/strong\u003e It goes +12 V only while the clutch relay is closed, so your ECU raises idle exactly when the compressor loads the engine.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eEverything else stays factory.\u003c\/strong\u003e Same plug, same sensors, same relays, same pressure switch.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cdiv class=\"callout\"\u003e\n\u003cstrong\u003e\u003c\/strong\u003e\u003cbr\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"callout\"\u003e\n\u003cstrong\u003eThis is the configuration it was built and driven on\u003c\/strong\u003e — a 1991 SW20 with a 2GR-FE and a manual gearbox. Not a design on paper waiting for a first customer to find the problems.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"media-card\"\u003e\n\u003cimg src=\"https:\/\/messerworksllc.com\/images\/sw20\/unit-exploded.webp\" alt=\"Exploded view of the controller: enclosure lid, populated PCB with relay, MOSFETs and screw terminal, and enclosure base with mounting bosses.\" width=\"1000\" height=\"1000\" loading=\"lazy\"\u003e\n\u003cp class=\"caption\"\u003eBoard, enclosure, and hardware. The whole assembly is 90 × 70 mm. The housing is printed in \u003cstrong\u003eASA\u003c\/strong\u003e — not PLA — so it holds its shape through a closed-up summer behind the dash and won't go brittle in UV.\u003c\/p\u003e\n\u003cp class=\"caption\"\u003e \u003c\/p\u003e\n\u003ch2 class=\"on-dark\"\u003eDesigned against the factory manual, not guesswork\u003c\/h2\u003e\n\u003cp class=\"section-lede center on-dark\"\u003eEvery terminal on the board was audited against the 1991 electrical wiring diagrams — page by page, wire by wire.\u003c\/p\u003e\n\u003cdiv class=\"eng-grid reveal visible\"\u003e\n\u003cdiv class=\"eng-item\"\u003e\n\u003ch3\u003eCopper-verified\u003c\/h3\u003e\n\u003cp\u003eThe routed 2-layer PCB was checked net-by-net against the netlist before a single board was ordered.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"eng-item\"\u003e\n\u003ch3\u003eFails safe\u003c\/h3\u003e\n\u003cp\u003eBoots with the clutch off. Loss of signal drops the compressor rather than latching it on. Reverse-polarity Schottky and a TVS sit at the supply input.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"eng-item\"\u003e\n\u003ch3\u003eThe traps are documented\u003c\/h3\u003e\n\u003cp\u003eIdentify the thermistor pair by measuring ~1.1 kΩ, never by pin number. The 12 V feed is R-L off the GAUGE fuse — not L-R, a different wire in the same loom. The W3 switch is a \u003cem\u003efan\u003c\/em\u003e switch, not an overheat cutout, and is deliberately unused. These are the mistakes that cost me time; they're written down so they don't cost you any.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"eng-item\"\u003e\n\u003ch3\u003e43 wires, each numbered\u003c\/h3\u003e\n\u003cp\u003eThe wiring guide is plain English, in order, with a full J1 position map. No schematic literacy required.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cfigure class=\"schematic reveal visible\"\u003e\u003cimg src=\"https:\/\/messerworksllc.com\/images\/sw20\/schematic.webp\" alt=\"Full wiring schematic of the SW20 A\/C controller showing every numbered connection between the factory A9 plug and the board.\" width=\"1600\" height=\"1639\" loading=\"lazy\"\u003e\n\u003cfigcaption\u003eThe complete schematic — included with every order, at every tier.\u003cbr\u003e\u003cbr\u003e\u003cspan\u003eOne screw terminal (12 to 15 positions, by unit). Every wire lands in a labeled position — no connectors to crimp.\u003cbr\u003e\u003cbr\u003eSealed printed enclosure with ziptie tabs — mounts where the old amplifier lived, or anywhere dry behind the dash.\u003cbr\u003e\u003cbr\u003e\u003c\/span\u003e\u003cbr\u003e\u003cbr\u003e\u003cbr\u003e\u003c\/figcaption\u003e\n\u003c\/figure\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/section\u003e\n\u003c\/div\u003e\n\u003c\/li\u003e\n\u003c\/ol\u003e","brand":"Messerworks LLC","offers":[{"title":"OEM Part Number: 88650-17120 - 91–92 USDM\/Canada - Europe LHD Dec 89 - Dec 91 - Auto and Manual 5S-FE or 3SGTE","offer_id":51511113285879,"sku":null,"price":189.0,"currency_code":"USD","in_stock":true},{"title":"OEM Part Number: 88650-17130 - 93–95 USDM and late-built 1992s. JDM Rev 2–5 and Europe Dec 91+","offer_id":51600595943671,"sku":null,"price":189.0,"currency_code":"USD","in_stock":true},{"title":"88650-17120 Swap Edition - Engine swapped (2GR-FE - 1MZ - K-Series...)","offer_id":51600595976439,"sku":null,"price":189.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1861\/6391\/files\/ACAmplifier.webp?v=1793235659","url":"https:\/\/mr2heaven.com\/products\/ac-controllers-amplifiers","provider":"MR2 Heaven","version":"1.0","type":"link"}