I got a brake fault light when the weather turned cold. It locked the brakes and I had to have it towed. The mechanic replaced a relay in the parking brake module which solved the problem until it turned cold again. I could drive it the second time. The mechanic replaced a relay again in the parking brake module. He then parked it outside the garage in the cold and I get a parking brake fault. Any suggestions?

 

https://www.jaguarforums.com/forum/s-type-s-type-r-supercharged-v8-x200-15/parking-brake-stuck-32699/

If above link doesn't work do an advanced search "parking brake stuck on" by "joycesjag" under the "S Type" directory.

 

The cold weather factor: This makes me suspect the battery. Cold weather is tough on a battery and causes the available voltage to drop. The EPB fault is one of the faults that can appear due to low battery voltage at engine start, even though the engine will fire up just fine.

Some interesting reading in these threads. Even though in these cases the problem was something other than the battery, there's still lots of good info to consider:

https://www.jaguarforums.com/forum/s...ilable-192080/

https://www.jaguarforums.com/forum/s...oltage-179828/

 

+1. Good advice from Karl. Also check out our "Battery 101 . . ." writeup as per my signature.

Cheers,

Ken

 

I thank you for the replies. Just have one more question. Would the low voltage of the battery keep causing the relays to burn up? Each time this happens there is a bad relay.

 

The $64 Question:

Have the relays actually failed? Consider this scenario. The battery is marginal and the voltage drops in the cold. EPB fault returns. Car is moved into the shop for repair and warms up. Or if the car stays put, a few hours elapse to get a new relay. Sun rises, warms things up, birds start chirping. Either way, the battery isn't as cold and self-recovers to some extent, enough to allow a start without an EPB problem.

Meanwhile, because the relay had been changed, it seems like it was the fix.

Now it is possible for low voltage to damage a relay, but usually only on high current circuits like heated seats, defrost grid, etc. With low voltage, the contacts don't clamp together as tightly as normal, which can cause arcing. Here's an example of arcing (AC compressor clutch), although I think this damage was due to old age, not necessarily from low actuating voltage:



If you have the old relays, pop off the cover to check for arcing damage.

The big test would be to check battery voltage before starting. From experience in this forum, 12.6v seems to be the magic number. Below that point, even though the engines cranks over and starts just fine, electronic faults seem to happen. If below that limit before start, further investigation is warranted. Could be a geriatric battery with one foot in the grave. Could be a drain running the battery down overnight. Could be a problem with the charging system. Could even be driving habits, such as only short infrequent trips, keeping the battery from getting fully recharged. It's possible to have several factors like that at the same time. These potential issues can all be ruled out by making sure the battery reads at least 12.6v before start.

Is that the fault you have? We can't know for sure, but it's super easy to check. There are many tales of woe on this forum of similar situations costing lots and lots of money, but the final fix was making sure the battery was up to snuff. It's just how modern cars are, sometimes.

 

Relays pretty much never keep on burning out so it's likely been misdiagnosed. Look for another explanation.

 

I posted earlier about an EPB Fault and the relays burning out. The mechanic had the car for a couple of weeks and told me it was in the emergency brake motor and said it needed replaced. I told him to check the battery first. He kept telling me that the battery cranked just fine. After a couple of weeks of arguing with him he finally checked the battery. Seems the battery loses charge just setting there. He replaced the battery. It solved the problem.

 

[QUOTE=richt1000;1806843 After a couple of weeks of arguing with him he finally checked the battery. Seems the battery loses charge just setting there. He replaced the battery. It solved the problem.[/QUOTE]

Woo hoo! Way to go! Thanks for the feedback, too.

 

Good news.
Now - I would replace the mechanic!

 

Hello, with the help of my Brother engineer i solved this way. It the brakes are stuck (you cannot nove the car) and there us a fault message just turn on the engine put the rear gear and force until the car moves. If doesnt put the 1st Gear and force. It will unstuck soon with no demage. Now Use the brake command to put and release the park brake. It will start working again. Turn off the car to reset the fault message and everything is fine now. If it us cold and tuo don t use the car much brake could stuck. I suggest to not put the brakes on of you do not use the car for many weeks expecially during winter. It is not an electrical problem but just a Mechanical problem. I hope this Will help you. Regards. Francesco form Milano.

 

I have had the same problem with brakes jammed on yellow dash light on. You can do a hard reset if you have the time,but it doesnt always work.Go into the boot and pull away carpet on right hand panel .
Behind carpet attached to inner wing is a control box with 2 plugs ,release both plugs and and push them back in. Start engine and away you go.

 

I have had the same problem with brakes jammed on yellow dash light on. You can do a hard reset if you have the time,but it doesnt always work.Go into the boot and pull away carpet on right hand panel .
Behind carpet attached to inner wing is a control box with 2 plugs ,release both plugs and and push them back in. Start engine and away you go.

 

I had the problem, which forced me to tow the car about 30 miles to our home. I tried the advice about unplugging the module in the trunk (boot) and it worked, sort of, but eventually I decided to just get a new battery.