B1859
Low Severity (Level 2)Climate Control A/C Pressure Switch Circuit Open
B1859 usually means climate Control A/C Pressure Switch Circuit Open.
Can you still drive with B1859?
⚠️Short-distance driving is usually OK, but have this diagnosed within a week to prevent further damage.
Typical repair cost: $60 – $900
Severity Level 2 — Low
This code indicates a minor issue that is unlikely to cause immediate driveability problems. You can typically continue driving but should have the vehicle inspected at your earliest convenience.
Common Symptoms
- Climate control not working — no response when activated
- Blower motor not working or only working on certain speeds
- A/C or heat output inconsistent — temperature won't adjust
- Infinite resistance in the climate control / HVAC circuit — broken wire or disconnected connector
Possible Causes
- Broken wire or connector pin in the climate control / HVAC system harness — common at flex points like door jambs or where wiring moves
- Disconnected or loose electrical connector — may have been bumped during other repairs
- Failed blower motor — internal open circuit from age, heat cycling, or vibration
- Corrosion completely severing a wire or connector terminal — green crust on copper wiring
- Wiring harness damage from rodent chewing — look for nesting material near the engine or under dash
Common Fixes
- Scan vehicle with a professional-grade OBD2 scanner to read all stored codes and freeze frame data — note the conditions when the code set ($8-127 at shop, free at auto parts store for basic scan)
- Visually inspect the climate control / HVAC system wiring harness and connectors — look for chafed wires, melted insulation, green corrosion, loose pins, or rodent damage (often free to check yourself, $125 diagnostic fee at shop)
- Trace the climate control / HVAC system wiring from connector to connector with a multimeter set to continuity/resistance mode — find and repair the break in the circuit ($101-246 labor for diagnosis and repair)
- Check and reseat all connectors in the climate control / HVAC system circuit — disconnect, inspect pins, clean with electrical contact cleaner, apply dielectric grease, and reconnect firmly ($17 DIY or $52 shop minimum)
- If blower motor has failed internally (open circuit inside), replace it — don't try to repair sealed components ($50-800)
Estimated Repair Cost
These are estimated costs based on generic repair data. Actual costs may vary depending on your vehicle, location, and labor rates.
Frequently Asked Questions
What does B1859 mean?
B1859 stands for "Climate Control A/C Pressure Switch Circuit Open". B1859 usually means climate Control A/C Pressure Switch Circuit Open.
Can you drive with B1859?
Short-distance driving is usually OK, but have this diagnosed within a week to prevent further damage.
How much does it cost to fix B1859?
Repair costs for B1859 typically range from $60 to $900, depending on your vehicle make, model, and local labor rates. Common fixes include: Scan vehicle with a professional-grade OBD2 scanner to read all stored codes and freeze frame data — note the conditions when the code set ($8-127 at shop, free at auto parts store for basic scan); Visually inspect the climate control / HVAC system wiring harness and connectors — look for chafed wires, melted insulation, green corrosion, loose pins, or rodent damage (often free to check yourself, $125 diagnostic fee at shop); Trace the climate control / HVAC system wiring from connector to connector with a multimeter set to continuity/resistance mode — find and repair the break in the circuit ($101-246 labor for diagnosis and repair).
Will B1859 clear itself?
Related Repair Costs
Explore Repair Costs
Related OBD-II Codes
These codes are in the same range as B1859 and often share similar causes and fixes.
Worried about repair costs?
Get transparent estimates and verify your mechanic's quote before authorizing repairs.
Related Discussions
See what other car owners are saying about this code and related repairs.
View B1859 discussions in the community