My rx 400h would not start i managed to get it to Lexus Chester they told me there water in the hybrid battery and they need to change a rely switch which i will cost me at least £1800.

Can anyone help surly theres a cheaper way to fix this problem 

Mark Smith

Dry the hell out of your car. The 400s are leakers. Then try clearing a code. Not convinced about the relay cost. Eye watering.

It sounds like the HV contactors, basically heavy duty relays, seem to remember reading about them and how to repair somewhere.

It may be worth asking Hybrid Batteries Solutions who are on this forum.

https://lexuspartsdirect.co.uk/product/lexus-rx400h-phase-2-hybrid-battery-relay/

Could you confirm the year of your RX400h?

Similar happened to me. Got a POAA warning with a 3 character INI. Mine was an isolation warning due to HB getting soaked!!

I dried my car out – and I mean bone dry – under carpets etc etc! Then I sealed the seams and hinge areas. Then I unhooked the battery. And lo and behold she started. I drove several miles and now keep several dehumidifier pots (silicate) in the storage area. Also removed some rubber bungs that impeded water exit under trunk area.

Try to get the codes first before spending any money.

 

 

This “relay switch” is located under the HV battery and according to a YouTube video I’ve seen, access to it means removal of the rear seats and battery. Hence Lexus labour cost of this work will be substantial.

This is the YouTube video I referred to above.  Access to the control unit only requires removal of the battery cover, not the whole battery.

Another RX400h video with power steering failure was diagnosed with a blown fuse located on the control unit.

Hiya, i also suffer with leaks into boot area, which needs lots of monitoring. Thanskfully it hasnt affected the battery units, yet

I taped the joints in the panels, just under the roof bar, but water is still getting in. Does anyone else know the other likely spots where the water might get in? 

I leave rags in the rear boot wells to soak up the water, they need to be ringed out every 2 - 3 days, also depends on the weather at the time. 

I’d appreciate your thoughts and advice 

Thanks. 

You need someone in the boot with a torch and someone outside with a hose. With a leak as bad as yours you should be able to spot where it's coming in. It's unlikely to be the seams, more likely a rubber seal.

5 hours ago, JasonH said:

You need someone in the boot with a torch and someone outside with a hose. With a leak as bad as yours you should be able to spot where it's coming in. It's unlikely to be the seams, more likely a rubber seal.

thanks, jason 

Rear light cluster gaskets? There are loads of posts regarding these leaking.

Bri

I had the POA66 codes for wet Hybrid battery. Dry it out. And I mean dry it out properly, bone dry.

LS-X trunk door hinges welds, seams, aerial area, roof rack plastic infill area.

Remove rubber bungs on metal floor behind battery. The drainage is poor. Look for ingress too around lights clusters.

Plumber's LS-X good sealing stuff.

Clear codes with TIS.

The above happened to me. Thought the battery was dead. Now fully recovered and car working like a beaut (126K miles). Had an industrial drier in the back of the car. Drier than a crisp after I'd finished.

 

 

 

Hi All

i had same code. Took it to Lexis to diagnose and they took back seats out. Said it was full of water. They have had it for four weeks and now say that it is beyond economical repair. It’s a 2008 RX 400 H I paid 6K . it’s in mint condition,  they want 12 K to repair it. They have stripped it down completely what do I do please help???. Any suggestions where I could take it ? 

On 4/21/2024 at 12:24 PM, JasonH said:

You need someone in the boot with a torch and someone outside with a hose. With a leak as bad as yours you should be able to spot where it's coming in. It's unlikely to be the seams, more likely a rubber seal.

Don't forget to let him out when you've finished.

On 4/23/2024 at 7:09 PM, Sasbambam said:

Hi All

i had same code. Took it to Lexis to diagnose and they took back seats out. Said it was full of water. They have had it for four weeks and now say that it is beyond economical repair. It’s a 2008 RX 400 H I paid 6K . it’s in mint condition,  they want 12 K to repair it. They have stripped it down completely what do I do please help???. Any suggestions where I could take it ? 

Good grief. Really not a great idea to leave the car with Lexus open ended. Always get a call before they eviscerate a vehicle. Often a very intense dry out and diagnostic error clear or aux battery isolation. Get them to put it back together.

On 4/21/2024 at 10:21 AM, long_ollie said:

Hiya, i also suffer with leaks into boot area, which needs lots of monitoring. Thanskfully it hasnt affected the battery units, yet

I taped the joints in the panels, just under the roof bar, but water is still getting in. Does anyone else know the other likely spots where the water might get in? 

I leave rags in the rear boot wells to soak up the water, they need to be ringed out every 2 - 3 days, also depends on the weather at the time. 

I’d appreciate your thoughts and advice 

Thanks. 

Dear Ollie (and all) - I bought my RX400H last year with the battery and relay repair already done in Lexus Poole with a vague mention of "modifications done". As the new owner I called them to dig into what that may mean and if ingress had been spotted and dealt with. They fobbed me off with "oh nothing really just tidying up" which seemed, frankly, a bit evasive and very poor considering the size of the bill! Not paid by me luckily.

Not long after purchase I saw water coming in during a downpour - at the rear of the roof corners, not from the hatch but further in. Looked to me like the roof itself/the roofrails were the issue.

Research led me to a few videos that had similar leaking from the roof so I removed the roof rails and roof trim pieces and re-sealed all the seams and also the bolt holes with sealant. For good measure I did all the panel gaps and hinges etc down the back of the car and just spent one of the wettest winters in Wales with no issues (crossed fingers).

I'm sure there are write-ups on here and elsewhere to show the way, it's not a huge job and the worst of it was getting the roofrail covers to ping off without snapping the tabs (only partially successful).

I had roof rail mounting points leaking on my 450h, one of the most common causes of the rear door power pack failure, where water gets in and destroys the PCB/electrics which are under the roof lining.  worth removing the roof rails (if you don't use them) and sealing the mounting holes or checking and replacing any rubber sealing washers (if used).  Also had some water getting in one rear light cluster.  It's another of the issues which may be more common than owners realise, and the only time you realise generally is when you start getting electrical issues with door lifts, batteries or rear lights.  The rail mountings are definitely a common source of water leakage.  Later models with integrated roof rails may not suffer the same issues.  

Not as bad as our older mid noughties merc C220 estate.  Had to virtually bail out the main fusebox and relay sump in the boot space every time we had a heavy downpour!