1. Engine Cooling Components Deals
  2. sku: 20648432556860773
  3. API TECH 27TPSQ

API SERVICE TECH 27TPSQ Engine Coolant Temperature Switch 5.7L V8

fits make: Chevy. year: 1990.

27tpsq Api Service Tech Engine Coolant Temperature Switch Fits Chevy C3500 1990 5.7l V8

( Brand: Api Service Tech ), ( Manufacturer Part Number: 27TPSQ ), ( Part Type: Switch Engine ), ( Engine: 5.7l V8 ), ( Compatible Make/model: Chevrolet C3500 ), ( Compatible Years: 1990 90 ), ( Fitment Info: Service Tech ), ( Manufacturer Warranty: 12 Month Warranty ), ( Attention: Read Full Description To Confirm Fitment ), ( Cs-sku: 400 )

Review API SERVICE TECH Engine Coolant Temperature Switch Chevy 5.7l V8 fits C3500 1990

The **27TPSQ Engine Coolant Temperature Switch** is a precision-engineered, high-performance component designed specifically for **1990 Chevrolet C3500 trucks** equipped with the legendary **5.7L (350 cubic inch) V8 engine**. This critical temperature sensing device plays a vital role in maintaining optimal engine performance, fuel efficiency, and longevity by monitoring the coolant temperature and relaying this information to the vehicle s electronic control unit (ECU). Crafted from durable **stainless steel and high-grade plastic**, the switch is built to withstand the demanding conditions of heavy-duty truck applications, ensuring reliable operation even under extreme heat and mechanical stress.

The **27TPSQ switch** features a **highly sensitive thermistor** a temperature-sensitive resistor that accurately detects coolant temperature fluctuations, triggering the ECU to adjust fuel delivery, ignition timing, and idle speed accordingly. This precision calibration helps prevent engine overheating, reduces emissions, and enhances throttle response, particularly during cold starts or high-load conditions. The switch is engineered to meet or exceed **OEM specifications**, ensuring a seamless fit with the **1990 C3500 s factory wiring harness and coolant system**, eliminating the need for modifications or additional adapters.

Beyond its functional excellence, this component is designed with **long-term durability in mind**, featuring a **robust mounting bracket** and **corrosion-resistant materials** to resist the harsh elements commonly encountered in commercial and off-road applications. Whether used in a **towing setup, fleet vehicle, or performance-oriented truck**, the **27TPSQ switch** delivers consistent performance, reducing the risk of false temperature readings that could lead to engine damage or inefficient operation. For owners seeking a **direct replacement** that restores factory reliability or upgrades their cooling system, this switch is an indispensable part of maintaining peak engine health in their **5.7L V8-powered C3500**.

### Pros and Cons of Buying a Replacement API Service 27TPSQ Engine Coolant Temperature Switch for a 1990 Chevy C3500 5.7L V8

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#### **Pros**

1. **Essential for Proper Engine Function** The coolant temperature switch (CTS) monitors engine temperature and triggers the cooling fan, preventing overheating. A faulty switch can lead to engine damage if the fan fails to activate.

2. **Prevents Overheating** Without a functional switch, the cooling fan may not engage when needed, risking catastrophic engine failure due to overheating.

3. **Common and Affordable Replacement** This part is widely available from aftermarket suppliers, making it cost-effective compared to engine repairs.

4. **Easy to Install** The switch is typically located near the thermostat housing and can be replaced with basic tools (screwdriver, socket set, and possibly a multimeter for testing).

5. **Compatibility with Aftermarket Parts** Many modern or upgraded cooling systems may require a reliable CTS to function correctly, especially if you ve modified your engine s cooling setup.

6. **Prevents False Diagnostics** A failing switch can trigger check engine lights (OBD-I) with codes like P0115, P0116, or P0117, leading to unnecessary diagnostic trouble. Replacing it resolves these codes.

7. **Long-Term Reliability** A new switch ensures consistent performance, reducing the risk of intermittent cooling fan activation or engine temperature fluctuations.

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#### **Cons**

1. **Potential for Counterfeit or Low-Quality Parts** Purchasing from untrusted sellers may result in a faulty or incompatible switch that fails shortly after installation.

2. **Misdiagnosis Risk** If the issue is not the CTS but another component (e.g., wiring, thermostat, or cooling fan relay), replacing the switch alone may not solve the problem.

3. **Testing Required** Before purchasing, you may need to verify the switch s functionality with a multimeter to confirm it s faulty, adding time and effort to the process.

4. **Wiring or Connection Issues** If the harness or connectors are damaged, replacing the switch won t fix the problem, requiring additional repairs.

5. **Limited Lifespan** While the switch itself is durable, it can wear out over time, especially in high-mileage vehicles or under extreme conditions (e.g., frequent short trips).

6. **Compatibility Concerns** Ensure the replacement switch matches the **API Service 27TPSQ** specification for your 1990 Chevy C3500. Mismatched parts may not fit or function correctly.

7. **Labor Costs (If Not DIY)** If you re not comfortable with automotive repairs, labor costs at a shop may offset the part s affordability.

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### **Conclusion**

The **API Service 27TPSQ engine coolant temperature switch** is a critical and relatively inexpensive component for maintaining your 1990 Chevy C3500 s cooling system. Replacing it is a straightforward fix for overheating issues, check engine lights related to cooling, or cooling fan malfunctions. However, it s important to:

- **Verify the switch is indeed faulty** before purchasing.

- **Source the part from a reputable supplier** to avoid counterfeit or incompatible units.

- **Inspect wiring and connectors** to ensure the issue isn t elsewhere.

- **Consider DIY installation** to save on labor costs if you re mechanically inclined.

If the problem persists after replacement, further diagnostics (e.g., thermostat, cooling fan relay, or radiator pressure cap) may be necessary.

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### **Recommendation**

1. **Test the Switch First** Use a multimeter to check resistance at different temperatures (cold vs. hot). A faulty switch will show inconsistent readings (e.g., not closing properly when hot).

2. **Buy from a Trusted Source** Purchase the **API Service 27TPSQ switch** from a well-known automotive parts retailer (e.g., RockAuto, Summit Racing, or an OEM supplier) to ensure quality.

3. **Follow Installation Steps Carefully** Refer to a repair guide or factory service manual for your 1990 C3500 to ensure proper routing of wires and secure mounting.

4. **Monitor Post-Installation** After replacement, watch for normal cooling fan activation and stable engine temperatures. If issues persist, revisit diagnostics.

5. **Consider a Thermostat Replacement** If the switch is working but the engine still overheats, the thermostat may be stuck closed, requiring replacement.

**Final Verdict:** Replacing the coolant temperature switch is a **worthwhile and cost-effective solution** for most overheating or cooling fan-related issues in your 1990 Chevy C3500, provided you confirm the switch is the root cause and use a genuine replacement.

Details:

API Engine Coolant Temperature Switch fits Chevy C3500 1990 5.7L V8 27TPSQ: Brand: condition: New Detailed Applications Years: Vehicle: Engine: 1990 Chevrolet C35005.7L. 12 Month Warranty.

part #: 27tpsq price

  • $31.56

specifications ocoosys:

  • for makes: Chevy
  • brand: Api Service Tech
  • mpn: 27tpsq
  • part type: Switch Engine
  • engine: 5.7l V8
  • compatible make/model: Chevrolet C3500
  • compatible years: 1990 90
  • fitment info: Service Tech
  • manufacturer warranty: 12 Month Warranty
  • attention: Read Full Description To Confirm Fitment
  • cs-sku: 400

seller ocoosys:

  • city: Overland Park, Kansas
  • rating: 99.1%
  • # reviews: 23497

payments ocoosys:

  • credit card: Discover
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  • wallet: Paypal

returns ocoosys:

  • paid by: Seller
  • time: 30 Days
  • policy: Returns Accepted

shipping ocoosys:

  • cost: $0.00
  • class: Economy
  • transit: 4-7 Days
  • service: Economy
  • type: Fixed

offer ocoosys:

  • started: March 27, 2026
  • sold: 0
  • quantity: 1
  • options: Ship-to-home
  • availability: In Stock

general ocoosys:

  • condition: New
  • Car Truck Parts Accessories > Engine Cooling Components > Other Engine Cooling Components
for makes: chevy, part type: switch engine, engine: 5.7l v8, compatible make/model: chevrolet c3500, compatible years: 1990 90, fitment info: service tech, manufacturer warranty: 12 month warranty, attention: read full description to confirm fitment, cs-sku: 400,
category: auto parts > car truck parts accessories > engine cooling components, sku: 20648432556860773,
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1 offer $31.56 USD
  • New. Offer #1 priced at $31.56 + $0.00 shipping estimate = $31.56* total. 12 Month Warranty 1990 Chevrolet C3500 5.7L V8.FREE SHIPPING

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