I Reversed battery cables on My 1992 Mercedes SL500. Now it turns over but won’t start

I hooked up battery cables backwards and blew something car turns over but won't start replaced OVP fuse 20amps still won't start

My car has 10000 miles.
My car has an automatic transmission.

Experienced mechanics share their insights in answering this question :
When the battery cables are reversed, It only takes an instant to do a lot of damage. The Alternator and the ignition modules are probably toast, And any or all of the ECU’s are probably damaged. The good news, if you can imagine any in this situation, is that this car was built before Mercedes started "marrying" control modules. That means you can do substitutions with a salvage car.if you can find one. Later Mercedes modules were matched to each other with a code so that chop shops could not get away with selling used modules but your car was built before this happened. Sorting this car out will take a technician skilled in electronics equipped with a lab scope. If you want to get some professional help with this, you can contact Your Mechanic to have a technician come out to your home or office to check out your car and give you an evaluation.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

The most common reasons a Mercedes-Benz 500SL won`t start are a dead battery, an alternator problem, or failed starter.
If you have a relatively new battery, though, but the engine won`t start, trickle charge your battery by using a 12-volt trickle charger. Fuse and relays. The fuse on your starter circuit, Ignition, EIS, or Fuel Pump should be checked next if the battery is not the issue.
The most common reasons a Mercedes-Benz SL500 won`t start are a dead battery, an alternator problem, or failed starter.
Check fuses and relays

Mercedes won`t start, and there are no batteries? You`ll need to check the vehicle fuses. Check the fuses for these certain parts, which are important: starter, ignition, engine ignition, and pump. It may vary from model to model whether a certain circuit affects starting.

The most common reasons a Mercedes-Benz S500 won`t start are a dead battery, an alternator problem, or failed starter.
The most common reasons a Mercedes-Benz CLS500 won`t start are a dead battery, an alternator problem, or failed starter.
When you have a brand-new battery but still can`t start the car, the alternator might be the issue. Cold and damp climates may increase wear on an alternator, causing it to fail. Flickering gauges and a burning rubber smell could indicate that the alternator overheated and requires replacement.
Why won`t my car start but the battery is good? If your car won`t start but the battery is good, the most common cause is a faulty starter – though it could also be to do with your fuel. You may have insufficient fuel to get the car going.
If your vehicle won`t start, it`s usually caused by a dying or dead battery, loose or corroded connection cables, a bad alternator or an issue with the starter. It can be hard to determine if you`re dealing with a battery or an alternator problem.
The most common reasons a Mercedes-Benz R500 won`t start are a dead battery, an alternator problem, or failed starter.
If the engine cranks slowly but doesn`t turn over, your Mercedes probably has a battery issue. When battery power is low or there is corrosion on the terminals, it will negatively affect your power output, and you`ll struggle to start your Mercedes.
The most common reasons a Mercedes-Benz R500 won`t start are a dead battery, an alternator problem, or failed starter.
These are: Your key fob battery is low or empty. This prevents the Electronic Ignition System (EIS) from functioning. The Driver Authorization System (DAS) is not functioning, and thus failing to verify the key properly when inserted into the ignition.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

I Reversed battery cables on My 1992 Mercedes SL500. Now it turns over but won’t start
ANSWER : When the battery cables are reversed, It only takes an instant to do a lot of damage. The Alternator and the ignition modules are probably toast, And any or all of the ECU’s are probably damaged. The good news, if you can imagine any in this situation, is that this car was built before Mercedes started "marrying" control modules. That means you can do substitutions with a salvage car.if you can find one. Later Mercedes modules were matched to each other with a code so that chop shops could not get away with selling used modules but your car was built before this happened. Sorting this car out will take a technician skilled in electronics equipped with a lab scope. If you want to get some professional help with this, you can contact Your Mechanic to have a technician come out to your home or office to check out your car and give you an evaluation.

Vehicle won’t start, once it’s jump started it only stays running until you turn it off, then it work start again without jumping.
ANSWER : Hi there. There could be two problems here. It is possible that your battery is bad and will not take a charge from your alternator while driving. In that case every time you shut your car off you will not have enough juice to start it again. Inspect your battery – it should have at least 12.5 to 13 volts to start your car, if it doesn’t you will need to replace the battery. The second problem could be that your alternator is bad and not charging your battery, in this case you will need to replace your alternator. Both the battery and the alternator can be tested in your car. If you would like to have the car checked for you, a certified professional from YourMechanic can come to your car’s location to diagnose the starting problem and proceed with repairs.

Car started with a jump start earlier today, but won’t start now despite turning over.
ANSWER : It’s possible that when you jump started the car the first time that an electrical relay may have been damaged. This is a very rare situation, but has been known to happen on some GM products like your Chevrolet Avalanche. It’s also possible that an ignition system component like the crankshaft position sensor or relay may also be faulty which wouldn’t be related to the battery. The best thing for you to do is have a mobile mechanic come to your home and complete a car is hard to start inspection, so they can pinpoint the source of your truck’s issues.

New battery & fuel pump. Hours later car starts and shuts down 3X in a row. Finally it starts, 48 hours later, won’t start at all
ANSWER : Checking all the fuses was a good move. I would also want to put a scan tool on it and check for diagnostic trouble codes (DTCs) as well as seeing the data that the computer is seeing.

A fuel pressure test would be a good idea to verify correct pressure and so that you’d be able to eliminate that possibility. It should be 58psi on your Magnum.

I also recommend getting your battery tested (I know, it’s new, have it tested anyway) and be sure it’s charged to at least 75%. And yes, loose battery cable connections can result in electrical problems.

If you need some assistance with this, consider enlisting a certified mechanic who can perform the checks I’ve mentioned and diagnose your starting issue firsthand. The mechanic can then perform the necessary repairs once the problem has been isolated. Good luck.

Fuel pump engages. Batery good, alternator good volts, jump start helps when wont start. Temp does not matter. Intermittent?
ANSWER : Hello. Thank you for writing in. There are several reasons your vehicle may only start when jump starting. The first and most common is a build up of resistance that is causing you to need a boost of voltage to get the engine started. This may be due to poor battery cables, a bad ground connection, a poor starter solenoid, and a couple of other issues. The first thing you want to do is perform a visual inspection of the starting system. Make sure there is no corrosion build up in the battery cables. You can also check the resistance across these wires and make sure you have a solid connection between components. You then want to make sure the starter solenoid is doing its job. It is responsible for taking the small amount of electricity sent by the ignition and turning it into a huge electrical charge that is strong enough to push over the engine with the help of some gear ratios in its favor. Do some more testing, and stick to the basics before assuming its something seriously complicated.

Car left two days didn’t start third day, lights go on, no start up. AAA battery charger started car.
ANSWER : Hello. It sounds like you have a battery issue. If the jump starting got the vehicle going then that means that the battery alone could not produce enough power to start the vehicle. If the battery is low enough it can power some of the lights and other electrical circuits in the vehicle and just not crank it. If you want to have your battery checked, consider YourMechanic, as a certified mechanic can come to you to [diagnose why the car does not start] https://www.yourmechanic.com/services/car-is-not-starting-inspection

My truck has problems turning over when I crank the engine (it won’t start), and my battery keeps draining.
ANSWER : Hi there, thanks for writing in. It sounds like your vehicle may be having a couple of problems. For the first problem, regarding the battery being drained and not charging back up, you will need to have the charging system checked to see if the alternator is faulty and/or needs to be replaced. For the second problem of no turning when cranking it, the issue may be that the starter is going bad from trying to crank it with a weak low battery, and may need to be replaced. If you would like help with having these inspections performed, consider having one of our expert automotive technicians come to your home or office to look at and diagnose these issues for you, and make any repairs as needed. Hope this helps and good luck!

Car won’t turn over. No lights come on when I turn it. Can’t even lock my doorsvor push the seat up or back.
ANSWER : Your probably correct, it sounds as though your battery is done. But it also sounds like you have charging system issues. I’m not sure that fixing your battery and charging system will solve the problem with the car shutting off, but it’s possible that it will and it’s a darned good place to start. By contacting Your Mechanic, you can have a technician come to your home or office to check out your car and help you figure out what to do next.