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Discussion Starter #1
I replaced my fuse box about 500 miles ago with new; in addition I relocated my RL7 relay externally. The basic theory I'm working under is the RL7 relay was under designed for the load it carries and over heats easily doing damage to the fuse box beneath it.

I was having problems with my fans really kicking out the volume of air desired, particularly at my feet. I live in a northern climate where heat is not a luxury but a necessity. After inspecting my old fuse box I discovered the widely known burnt and cracked fuse box around the RL7 relay area; along with a browned RL7 relay that showed evidence of overheating. I tried just installing a new relay and cleaning up the contacts with an emory board but after one day of driving the new relay was scorched as well and my fan speed dwindled again. I ordered a new part number correct fuse box off of ebay. The stickie in "Common Problems" will help you with that.

http://www.rangerovers.net/repairdetails/electrical/fusebox.html

Rather than try to repeat the problem I decided to relocate the RL7 relay. This was discussed in a previous post some time ago. With 500 miles on this design the relay and fuse box still look new. And my fan speed runs at max for much of the short trips I do. (Spring is coming, but not quite yet.) There is actually quite a bit of airflow at my feet now, and the "Open Book" symbol has disappeared from the display.

By using short 12 gauge solid copper wire with male and female spade connectors, with everything soldered together it is a tight connection. Heat shrink tubing was utilized along with a rubberized coating material that was painted onto the female connectors against the relay. Silicone was added to the fuse box open area for a fairly water tight environment.




I utilized a small piece of plastic (old fuse box cover) and extended a small platform to zip tie the relay to. Between the relay and the plastic is a small piece of felt (like what you put on the bottom of a chair on a wood floor) to cut down on the vibration on the relay. I'll watch that closely for a while for evidence of overheating.





The battery box cover had to be slightly modified to accommodate the relay location.

 

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Neat job.
As RL6 feeds the right blower motor, are you planning to move that one as well?
 

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Very nice job indeed.
The cool thing is that now that you have the relay outside, you could easily use a 40 amp version rather than the 30 amp rated stock relay, in case it keeps overheating.....
 

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I wonder why only one relay is overheating, and not the other ?? Both RL6 & RL7 are fed from separate 25A fuses, so 30A relays should never be overloaded. Maybe one blower is sticking or faulty ?

I suspect it's more likely the relay socket contacts age & corrode, hence causing resistance between the PCB and relay. This then causes localised heating, eventually damaging the PCB.
 

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Make sure your vent pollen filters are not clogged it can overheat the fans
 

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I wonder why only one relay is overheating, and not the other ?? Both RL6 & RL7 are fed from separate 25A fuses, so 30A relays should never be overloaded. Maybe one blower is sticking or faulty ?

I suspect it's more likely the relay socket contacts age & corrode, hence causing resistance between the PCB and relay. This then causes localized heating, eventually damaging the PCB.
Good question, of course something could be faulty, but seeing as "They all do this" I suspect not an issue with a fan.
I believe it is a combination of overcrowding the relays, and running them close to spec.
It may sound repetitive, but "The hotter they get, the hotter they get"
The burnt board issue is caused by close proximity to the hot relay contacts which are being heated by the current running through them and transferring said heat to the plastic and the Board.
Over time the contacts will anneal, and lightly oxidize, then they will get even hotter, and so on to burn out.
I hope we get an update after this summer when the Air Con will be used as well. If we see zero relay issues, we will know more.......
 

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Discussion Starter #8
I readily admit that this is experimental. The theory that the filters are clogged and/or the wiring is longer to the left fan cause this relay to burn out are not the root cause of failure. Something else is causing these relays to overheat, it may be a design issue within the fuse box itself??? I don't know for sure.

I like this Rover and plan to keep it. But it will not be the workhorse it once was; this machine came with a flat five pin trailer light hook up, so that tells me someone use to pull a heavy sled behind it. My Rover will run 5000 miles a year in a northern climate, not exactly the Serengiti Desert.

But I will post up any developments, no news is good news though.
 

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Discussion Starter #10
Update

I've seen another thread lately on this topic so I'd thought I would just update my findings on this modification after a run today, and about an additional 1000 miles since the last update.


All is good.

Ran the Rover today with the AC on for a good 2 hours at highway speed (62mph, 100KM) average. Outside air temp of 75 F (24 C), engine gauge temp stayed vertical on the cluster scale. This is the first time I ran the AC since the new fusebox, new relay and relocated relay. The fan ran on high the entire time with cold air blowing and the sunroof open. I didn't need to run it on high but I wanted to test the relay.

The pictures show no discoloration of the relay; so, no excess heat so far. I've read other experimental repairs of the RL7 issue that are more extensive but this limited confined modification may be all that is needed. I will update again mid summer, but so far everything looks good.

David


Pictures taken today:



 

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how hot is to hot ? the other day I lent into a jeep that was having trouble on the sand tracks (traction control still on) and nearly burn't my arm . every thing under the bonnet was hot, to hot to hold on to
 

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Ahh, A Hoon in the Dunes! (Great memories)
Tazzie has some truly epic dunes and beaches! (Watch for the quicksand!)
Would it not be reasonable to expect any vehicle to get screaming hot under bonnet
if you have been going at full tilt yet probably fairly low speed?
I think the fuse/ relay board on these trucks was just made a bit too tight for the number of amps being shunted through them, thus they run hot under even the best of conditions.
 
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