Recently acquired a 2005 Coupe with 45k miles that had been little used in recent years. Looks like it has suffered some water ingress that has interfered with electrics - I have recently replaced the Engine Management Control Relay (A 170 545 03 05) which has resolved many of the issues, but a couple still persist.

With key removed, the driver side external lights are on. With the key in and turned, the right arrow indicator is stuck on in solid display on the dashboard in addition. If I remove the 35 position fuse from the fuse box (is there a better name for this component?) it lets me leave them off so the battery doesn't drain. I am aware the lights **** must be in the fully off position as single sided external lights are a feature on the car. I have tried the switch in every position and it works as intended except for the single sided lights feature.

Additionally, the radio is stuck on when the car is on and doesn't display or allow me to turn off. The rear spoiler motor is flashing red on the switch and doesn't work but unsure if this is an issue with the motor or with the fuse box as well. Do I seek to replace the fusebox? I believe it is the set of components outlined in this diagram but I don't know what the ID number for the whole fuse box would be. Thank you!

 

Did it actually get water in the fuse box?

 

Tear the trim from the rear area and get to the CLP/SSM. Unplug every connector and look for water intrusion and corrosion. Water damage to the CLP/SSM is common in Roadsters and way less common but not unheard of in Coupes. Damage that water causes will cause many of your symptoms (wing issues, lights that stay on, battery drains on it's own....) I would look at that first.

No, I"ve never owned a coupe and don't know how to get to it in the coupe but I've replaced several CLP/SSMs in Roadsters with this issue.

IF you find water damage, you need a CLP/SSM from a 'donor car', they require no programming and all CLP/SSMs in Coupes, Roadsters, SRT6s, etc - are the same. Also, get the last 2-3 feet of wiring harness as you can not clean the pins of the connectors once they are corroded.

IF you find no damage, you can move on to other suspects.

 

1) Cars that sit can be a real PITA for a while. Mine had sat 20 months and it took over a year to work thru the issues.
2) This statement is not helpful, you talk of water intrusion and the RCM - did the RCM get wet? If so, HOW? The RCM can't get wet without the BCM and ECU getting wet and it can't get wet if that cover is on the box. Please make clear what you mean by "water intrusion".

Fuse 35 feeds the SKREEM, as well as the turn signal relay that drives the pulsing of the of turn signals on FOB signal reception. If that fuse causes ANYTHING other than the turn signals to go out, you have one hell of a problem with the car.

The radio staying on and not letting you turn it on or off is because the original heads in these cars are dying left and right. DOn't get distracted by this, let's fix the rest of us issues first. The wing switch flashing and the wing not working is certainly a strong clue, but again, did the big box next to the battery get wet inside? If so, you will be needing more than an RCM.

You cant "replace the fuse box" but you can get some parts for whats' inside.

Did water get in the fuse box?

 

Thanks for the answers

With some difficulty removed the rear trim to access the CLP - there was significant water pooled and have since dried out everything, thanks for pointing me there.

Interestingly, the indicator lights stayed on with CLP removed. The day after I reinstalled it the functionality of the passenger side indicator returned, and the day after that both sides are now working. However, I have lost the functionality of my central locking system now.

There was a very small amount of corrosion visible on the CLP that I could try to clean up? Central locking switch in car doesn't lock or unlock doors so not a key fob issue. I am also concerned I did not put the three yellow wires with grey connectors into the same slots on the airline manifold - I realise now I could have simply disconnected the manifold.

Also, I have replaced the radio head unit with an aftermarket radio - radio display works fine

but there is intermittent sound as with previous OEM head unit. Photo attached of removed unit for interest as there was visible damage. Do I check fuses, or check the connection to the amp under the floor?

 

That radio has been getting wet for some time. If water is getting into the ICM (headlight switch assembly), then all bets are off about what damage has been done.
Intermittent audio output is not a fuse, I'd pull the carpet up on the passenger side and get to the power amp and look for water intrusion.

 

Were the drains under the cowl plugged? Were the windows left down for a period of time? It looks like the interior of a roadster left in the rain with the top down.

 

Not sure on the conditions in which it was stored - largely unused for a few years as far as I can gather. It was also very grimy when I picked it up so it did receive a very thorough wash. I worry that some water soaked into CLP during the wash but I think there is enough evidence that there has been significant damp issues accumulating over time as the radio damage suggests.

I'll check if the drains are plugged, slightly worried that this could invite water ingress rather than relieve it but have read a post about warping them slightly to prevent this so might try that. I'll have a look at the amp as well and see what meets the eye. Thanks again.