A family member has a Volvo 850 (1996) and had a crash. Now the seat belt pretensioners have locked the seat belts solid. I've tried resetting the ECU, took it to Volvo and they wanted to replace the whole seat belt mechanism (in Asia so they try to take as much money off him as possible, regardless of whether that is right or not). I'm thinking there must be a pre-tensioner fuse or something which could be taken out. The hydraulic (I assume) rods are at full tension inside the panels of the seat belts and it's actually ripped the panel plastic itself. Any ideas on how to reset the belt mechanism?

Heating and the cooling both don't work ? Just one seat or all seats ?
Your best bet have it checked for DTC'S - diagnostic trouble codes to start .
Climate Controlled Seat Module (CCSM) Diagnostic Trouble Code (DTC) Index DTC Description Source Action B1342 ECU Is Faulted CCSM INSTALL a new CCSM and CARRY OUT programmable module installation (PMI). REFER to Climate Controlled Seat Module . B1358 Ignition Switch or Blower Electronics Circuit Short to Ground CCSM Go To Pinpoint Test Q . B2477 Module Configuration Error CCSM This DTC indicates programmable module installation (PMI) has not been done to a newly installed module. CARRY OUT PMI. REFER to Section 418-01 . CLEAR the DTC. CARRY OUT the self-test. B2486 Climate Controlled Seat Module Voltage Out of Range CCSM DEPOWER the supplemental restraint system (SRS). REFER to Section 501-20B . DISCONNECT driver safety belt buckle pretensioner electrical connector or passenger safety belt buckle pretensioner electrical connector of the affected seat and CONNECT restraint system diagnostic tool 418-F395 to the safety belt buckle pretensioner harness connector. CONNECT the battery ground cable. CHECK circuit 294 (WH/LB) for a fault. REPAIR as needed. If okay, REFER to Section 414-01 . Once the repair is complete, DISCONNECT the restraint system diagnostic tool from the safety belt buckle pretensioner harness connector and CONNECT the safety belt buckle pretensioner connector of the affected seat. REPOWER the SRS. REFER to Section 501-20B . B2488 Thumbwheel Switch Voltage Out of Range High CCSM Go To Pinpoint Test R . B2521 Tach Circuit Failure CCSM Go To Pinpoint Test Q . B2729 Cushion Over-Temp Detected CCSM Go To Pinpoint Test S . B2730 Back Over-Temp Detected CCSM Go To Pinpoint Test S . B2731 Differential Temperature Fault CCSM Go To Pinpoint Test S . B2792 Heat Switch Short to Ground CCSM NOTE: If HEAT is pressed for greater than 20 seconds on the climate controlled seat switch, DTC B2792 will set in the CCSM.
CLEAR the DTC. If the DTC does not clear, DEPOWER the supplemental restraint system (SRS). REFER to Section 501-20B . DISCONNECT driver safety belt buckle pretensioner electrical connector or passenger safety belt buckle pretensioner electrical connector of the affected seat and CONNECT restraint system diagnostic tool 418-F395 to the safety belt buckle pretensioner harness connector. CONNECT the battery ground cable. CHECK circuit 1551 (VT/WH) for a short to ground. REPAIR as needed. If okay, INSTALL a new climate controlled seat switch. Once the repair is complete, DISCONNECT the restraint system diagnostic tool from the safety belt buckle pretensioner harness connector and CONNECT the safety belt buckle pretensioner connector of the affected seat. REPOWER the SRS. REFER to Section 501-20B . B2793 Cool Switch Short to Ground CCSM NOTE: If COOL is pressed for greater than 20 seconds on the climate controlled seat switch, DTC B2793 will set in the CCSM.
CLEAR the DTC. If the DTC does not clear, DEPOWER the supplemental restraint system (SRS). REFER to Section 501-20B . DISCONNECT driver safety belt buckle pretensioner electrical connector or passenger safety belt buckle pretensioner electrical connector of the affected seat and CONNECT restraint system diagnostic tool 418-F395 to the safety belt buckle pretensioner harness connector. CONNECT the battery ground cable. CHECK circuit 1550 (WH/OG) for a short to ground. REPAIR as needed. If okay, INSTALL a new climate controlled seat switch. Once the repair is complete, DISCONNECT the restraint system diagnostic tool from the safety belt buckle pretensioner harness connector and CONNECT the safety belt buckle pretensioner connector of the affected seat. REPOWER the SRS. REFER to Section 501-20B . U2362 UBP Invalid Data Node ID CCSM NOTE: DTC U2362 indicates a network concern, the CCSM is not the source of the fault.
CLEAR the DTC. If the DTC does not clear, REFER Section 418-01 .

DTC B0058 Right Front/Passenger Pretensioner Deployment Loop Open.
The passenger seat belt pretensioner deployment loop consists of a seat belt pretensioner-RF and the seat belt pretensioner-RF high and low circuits. A shorting bar used within the seat belt pretensioner connector shorts together both the seat belt pretensioner high and low circuits when the connector is disconnected. This will help to prevent unwanted deployment of the pretensioner during servicing. During a frontal crash of sufficient force the inflatable restraint sensing and diagnostic module (SDM) will allow current to flow through the deployment loop in order to deploy the seat belt pretensioner. The SDM performs continuous diagnostic tests on the deployment loops to check for proper circuit continuity and for shorts to ground or voltage. If a malfunction is detected, a diagnostic trouble code (DTC) will be stored in memory.
DTC B0084 Left Front/Driver Seat Position Sensor Circuit
The inflatable restraint seat position sensor (SPS) is used to determine the proximity of a front driver or passenger seat position with respect to the frontal air bag. The SPS interfaces with the sensing and diagnostic module (SDM). The state of the SPS allows the SDM to disable stage 2 of the frontal air bag for a front seat that is forward of a forward/rearward point in seat track travel. The SPS is a hall effect sensor that is mounted on the inside seat track of both the driver and passenger seats. The seat track includes a metal bracket that shunts the SPS magnetic circuit creating 2 states of seat position. The shunted state represents a rearward seat position. The non-shunted state represents a forward position. The SPS provides 2 current ranges, one range for the shunted state and a second range for a non-shunted state. These 2 states are inputs to the SDM. State 1 (shunted) being the rearward threshold and state 2 (non-shunted) being the forward threshold. When the SDM receives input from a SPS that state 1 threshold is reached (seat is rearward) the SDM will not disable stage 2 deployment, if required by the deployment sensors. When state 2 threshold is reached (seat is forward) the SDM will disable stage 2 deployment on the side the seat is forward. The SDM monitors the SPS circuit and if a fault is detected the SDM will set codes B0083 or B0084 and defaults to disabling stage 2 frontal deployment. This will only default on the side of the vehicle the sensor has a fault. Its important to understand that the SPS is secondary to the passenger presence system (PPS) and the manual instrument panel (I/P) module disable switch. If either one of these devices are in the disable mode the passenger air bag will not deploy regardless of the SPS status.
You should take this to a qualified repair Shop ! Takes special tools to test .

Code B001b is for Sensing Diagnostic Module (SDM) for Air bag.

Potential Causes:-

• Drivers Seat Belt Anchor Pretensioner
• Passengers Seat Belt Anchor Pretensioner
• Sensing Diagnostic Module (SDM)
• Sensing Diagnostic Module (SDM) Wiring

1. Confirm the passenger seat belt anchor pre tensioner connector position assurance is clicked into place.

2. If not, click it in and retest.

3. If the codes reset, disable the Supplemental Inflatable Restraint (SIR) system.

4. Substitute a 2.0 to 2.2 ohm resistor for the passenger seat belt anchor pretensioner. Refer to Tech Tips for a load tool.

5. Retest for the code to reset.

6. If the code resets, check for harness problems between the seat belt anchor pretensioner and the Sensing Diagnostic Module (SDM).
Tech Tips: At the beginning of the 2009 model year, the Impala began being equipped with two pre tensioners for the driver and two pre tensioners for the front passenger. The first pretensioner is still attached to the seatbelt retractor. The second pretensioner is attached to the anchor point for the seat belt.
A load tool can be fashioned from an 1157 light bulb and socket. Turn the bulb into the socket. Using an ohmmeter, determine which 2 wires have 2 - 3 ohms of resistance. Use those 2 wires as the load tool.

I’m happy to assist further over the phone at https://www.6ya.com/expert/uttamjeet_2f3adc18600f8ede

what exactly does lock mean.
say what you cant do, or what is wrong.
exactly.

my guess, is the pretensioner has failed and is stuck out. flapping belt in breeze>?
ok, open the cover and unjam it.
if you are DIY that is easy if not read the FSM book, it covers this in vivid details. (lots of pages, lots of ways to mess up)
or get help.
id dont think alldata.com will cover this device.

there is a pretensioner in the seat belt buckles that go off when the air bags go off

There appears to be a pattern of premature failure of seatbelt pretensioners in the mid-2000s Gran Marquis, especially the 2005 model year. See carproblemzoo.com or NHTSA complaints. Ford dealer wanted $103 for diagnosis and $501 for replacement of the part.

dont think you can it should reset itself when you turn ignition off and on again but its a merc so no doubt its done like this so its a dealer only job ,hope you have lots of wedge to pay the dealer

most new cars have seat belt pretensioners that fire with air bag deployment these must be replaced.

look to see if you can adjust your seat belt pretensioner to better suit your height. look at the top of your seat belt- ( driver's side up and to the left of your left shoulder ) and see that you can very easily slide up or down your seat belt pretensioner. you are actually supposed to do this and even redo it if you ever readjustt your seat up or down or forward or backwards. believe it or not, your safety airbag light will come on automatically until you adjust your seat belt pretenioner in a way that the sensors read your seat belt to be safely set. naturally, if someone else drives the car he or she might have to readjust the seat belt pretensioner for the sensors to read them as being safely put. do this and the airbag warning light should go out.