Range Rovers Forum banner
1 - 20 of 49 Posts

·
Registered
Joined
·
19 Posts
Discussion Starter · #1 ·
OK. I now am on my 4th fusebox in 12 years of ownership of my p38. I placed all three burned fuseboxes side by side, and all three are burned at the RL7 relay (LH Blower Motor). Even the carbonized burn marks are identical in shapes. My local Land Rover Stealer (who are actually pretty good guys) just today told me that they still just change out fuseboxes and that there is no technical service bulletin for this problem. Well, simply refitting fuseboxes is not an acceptable engineering practice in my book when we KNOW that a burn will result. This isn't a hypothesis anymore, it's almost a scientific law by now. Isn't stupidity defined as doing the same thing over and over and expecting a different result? Also, this BS about pollen filters clogging and causing the LH Blower Motor to work too hard is pure nonsense. If clogged pollen filters were causing this problem, then we would be seeing burns on the fuseboard at RL6 (RH Blower Motor) as well. But there are not any instances of of burned fuseboxes at RL6 that I know about. They are all at RL7. I have had enough of this BS!! I am not finding any solution on the internet in general or this website. Has somebody come up with a solution?

I am interested in soliciting ideas for a solution that actually works. So far I have come up the following:

1. create a 4-wire pigtail with 10 ga wire and remotely locate the RL7 relay OUTSIDE the fusebox.
2. take a Bosch-style ECU cooling fan and cool the fusebox.
3. run a really heavy (8ga) primary wire from the fusebox to the LH blower motor to reduce resistance.

Does anybody have a better idea? or any idea that that actually can make the RL7 portion of a fusebox last longer than 2 to 3 years?

Tom

1996 4.6
228k miles
LR322 modified expedition rack
 

Attachments

·
Registered
1970-1995 Range Rover Classic
Joined
·
2,032 Posts
I got a 40 amp relay and used it in the RL7 position. Its just a standard 40 amp headlight relay I bought at a car parts store.

I've had it in there for over a year. It stays cooler and then the stock unit.

I'm sure someone will chime in that I'm wrong and it won't work. But so far its been just fine. When i got my rover the fuse box burned up with in a week and that relay was the problem. I found one that fit the location and worked the same way. I installed the new fuse box over a year ago and I still have not had any over heating issues. I run the heater and heated seats all winter.

I can take a look and see if I can get a part number and manufacturer tomorrow.
 

·
Registered
Joined
·
931 Posts
OK. I now am on my 4th fusebox in 12 years of ownership of my p38. I placed all three burned fuseboxes side by side, and all three are burned at the RL7 relay (LH Blower Motor). Even the carbonized burn marks are identical in shapes. My local Land Rover Stealer (who are actually pretty good guys) just today told me that they still just change out fuseboxes and that there is no technical service bulletin for this problem. Well, simply refitting fuseboxes is not an acceptable engineering practice in my book when we KNOW that a burn will result. This isn't a hypothesis anymore, it's almost a scientific law by now. Isn't stupidity defined as doing the same thing over and over and expecting a different result? Also, this BS about pollen filters clogging and causing the LH Blower Motor to work too hard is pure nonsense. If clogged pollen filters were causing this problem, then we would be seeing burns on the fuseboard at RL6 (RH Blower Motor) as well. But there are not any instances of of burned fuseboxes at RL6 that I know about. They are all at RL7. I have had enough of this BS!! I am not finding any solution on the internet in general or this website. Has somebody come up with a solution?

I am interested in soliciting ideas for a solution that actually works. So far I have come up the following:

1. create a 4-wire pigtail with 10 ga wire and remotely locate the RL7 relay OUTSIDE the fusebox.
2. take a Bosch-style ECU cooling fan and cool the fusebox.
3. run a really heavy (8ga) primary wire from the fusebox to the LH blower motor to reduce resistance.

Does anybody have a better idea? or any idea that that actually can make the RL7 portion of a fusebox last longer than 2 to 3 years?

Tom

1996 4.6
228k miles
LR322 modified expedition rack
I would suspect that you are treating the symptom .by replacing the fuse box,rather finding the cause.The blower is not just a motor,but an assembly with other controls in the unit.As the feed from RL7 supplies the motor as well as other items in the assembly there could well be an over current situation there.

I have a 1995 4.6 and RL7 and fuse box after 7 years of my ownership have not been replaced.
Anyway these are my thoughts on the issue.
 

·
Registered
Joined
·
375 Posts
I also had the same problem with my ´95 4.6 - when I bought it the book symbol was showing and it turned out to be the RL7 relay that was burnt also. I took my old relay to an auto electric supplier and asked for another relay but of the same type. That was over a year ago and I have had no problems since. I do need to replace my fuse box (still the original item) and that is on the list of things to do soon.

I recall seeing a post regarding the overloading of the relays and it was suggested (if I recall correctly) that the relays should be replaced with modern equivalents and that should cure the burning problem. It was something about the relays not liking their environment under the bonnet.
Please correct me if my memory has failed me.

check this out: http://www.rangerovers.net/forum/7-range-rover-p38a-mark-ii/36632-fuse-box-cure.html
 

·
Registered
Joined
·
19 Posts
Discussion Starter · #5 ·
Hi John,

Well I have to say that after 7 years of ownership I am certain that you would find a very crispy fusebox if you opened it up. I am curious. . .if you remove your RL7 relay are you telling me that there is no evidence of melting of plastic on the fuse board and that the RL7 relay itself is not "browned" in any way? Just because you haven't replaced it doesn't me that it hasn't overheated. please respond to this point. i am very curious.

I do take your suggestion to heart as this is a chicken and egg thing. Immediately prior to replacing the fuseboard for the 4th time, the LH blower motor started working only intermittently due to a pitted commutator. If the blower motor stopped on the damaged portion of the commutator then it would not restart until i rapped it with a hammer. Also the red wire on the blower motor had been heat damaged for many years. so it is possible that i had less than ideal conditions for many years with respect to the LH blower motor. I admit that I am a bit ignorant on the effects of a failing electrical DC motor, and I would like to hear from anybody who can illuminate and perhaps relate this to the the overheating relay problem. I am open to the possibility that the blower motor caused the relay to overheat, but maybe the relay runs too hot to begin with. so i am still not sure which causes which.

I would suspect that you are treating the symptom .by replacing the fuse box,rather finding the cause.The blower is not just a motor,but an assembly with other controls in the unit.As the feed from RL7 supplies the motor as well as other items in the assembly there could well be an over current situation there.

I have a 1995 4.6 and RL7 and fuse box after 7 years of my ownership have not been replaced.
Anyway these are my thoughts on the issue.
 

·
Registered
Joined
·
931 Posts
Hi Thomas,
I will take a look at the fusebox next time I am under the bonnet.I am certainly not saying that mine is not affected by heat.I do believe that relays are being operated very close to their operational limit and of course under bonnet heat from the engine does not help matters.
But what I do believe is that your experience is not the norm and the fuseboxes should last longer than you have experienced.There must be a reason for this and I was suggesting a possibility.Prehaps for some reason your under bonnet temperature is higher than normal.I do not know the answer for sure,but I am sure you dont want to continually renew the fusebox.So a bit of lateral thinking is probably required in this case.
Hi John,


Well I have to say that after 7 years of ownership I am certain that you would find a very crispy fusebox if you opened it up. I am curious. . .if you remove your RL7 relay are you telling me that there is no evidence of melting of plastic on the fuse board and that the RL7 relay itself is not "browned" in any way? Just because you haven't replaced it doesn't me that it hasn't overheated. please respond to this point. i am very curious.

I do take your suggestion to heart as this is a chicken and egg thing. Immediately prior to replacing the fuseboard for the 4th time, the LH blower motor started working only intermittently due to a pitted commutator. If the blower motor stopped on the damaged portion of the commutator then it would not restart until i rapped it with a hammer. Also the red wire on the blower motor had been heat damaged for many years. so it is possible that i had less than ideal conditions for many years with respect to the LH blower motor. I admit that I am a bit ignorant on the effects of a failing electrical DC motor, and I would like to hear from anybody who can illuminate and perhaps relate this to the the overheating relay problem. I am open to the possibility that the blower motor caused the relay to overheat, but maybe the relay runs too hot to begin with. so i am still not sure which causes which.
 

·
Registered
1995-2002 Range Rover P38A
Joined
·
1,851 Posts
Hi

On the main site is a story on fuse box repair under common faults and fixes.

It is a fact that the copper layer that is used to supply power to the relay 7 is not big enough for the current draw from the fan. This in combination with bad position of the fuse box in the hot area of the engine bay and possible bad connections on the relay causes overheating and discolouration of the pcb board. I have had the same problems and was having problems with the fan starting and the fuse melting. The fuse did not blow but the plastic part melted as one of the connectors was having bad contact and the heat generated here melted the plastic of the fuse and also the red tool to pull out the fuses.

I took my old fusebox and opened it up by cutting all connections at the side and bending open the pcb boards. I soldered extra wires from the connectors to the fuse and relay feet. At did this for both fan relays as both of them have discoloured tracks on the PCB. At the repair page from RRnet it is stated that the pcb was repaired by putting on extra layer of solder at the pcb tracks that were discoulered, which made me decide to solder the wires on to make extra low resistance path for the required current. After soldering I covered the pcb's with insulation spray and left the plastic board out to have better cooling between the boards.
Do not cover the outside 1 cm with insulation spray as you need to solder there, mask it before applying the insulation spray.
I took out all cut connections and replaced these with copper wire that I soldered back together. I had one connection where the copper came partly loose from the board but I soldered a layer on top until all was solid. I removed the solder grease with washing down the soldered areas with electroclean. After this it was putting back the plastic surround.

It is now fitted in my car and performs without any problems so far.
Hopefully you are able to do the same with your old fusebox and will not have any problems again with the blowers.

Regards

Jos
 

·
Registered
1970-1995 Range Rover Classic
Joined
·
2,032 Posts
Here is what i did. nothing special, handles the load better the stock 20 amp relays. There is no reason to hack up the wiring or the fuse box.

And its simple and easy. I run my seat heaters and fans on high a lot in the winter when i first start it up.

As you can see in the photos the relays work the same way. No special rocket science here.



New 40 amp relay. No burn marks on my fuse box with this in there for over a year.



Stock relay

 

·
Registered
Joined
·
19 Posts
Discussion Starter · #11 ·
Also, position 85 on the RL7 socket on the fuseboard is reading 12v with ignition off and 1v when ignition is on and fuse detached. does anybody know if this is normal? i thought that position 85 was ground and that the BECM would provide a ground when it wants the blower motors to operate. why would position 85 have any voltage at all until the ground was applied with the relay plugged in. . .could somebody please demystify this for me. . .I'm an electrical newbie.
 

·
Premium Member
Joined
·
2,565 Posts
I do take your suggestion to heart as this is a chicken and egg thing. Immediately prior to replacing the fuseboard for the 4th time, the LH blower motor started working only intermittently due to a pitted commutator. If the blower motor stopped on the damaged portion of the commutator then it would not restart until i rapped it with a hammer. Also the red wire on the blower motor had been heat damaged for many years. so it is possible that i had less than ideal conditions for many years with respect to the LH blower motor. I admit that I am a bit ignorant on the effects of a failing electrical DC motor, and I would like to hear from anybody who can illuminate and perhaps relate this to the the overheating relay problem. I am open to the possibility that the blower motor caused the relay to overheat, but maybe the relay runs too hot to begin with. so i am still not sure which causes which.
this i would say is your biggest clue, resistance = heat, which equals more resistance which equals....and so on.
 

·
Registered
1970-1995 Range Rover Classic
Joined
·
2,032 Posts
i that relay is for the EAS right? I don't have that, and the relay has never been in there, atleast since I've owned it.
 

·
Registered
1995-2002 Range Rover P38A
Joined
·
1,851 Posts
Hi

The relay on position 10 is the modification of the Hevac system and is used to switch power to the ac compressor clutch.

As for the use of other relays, I am using old ABS pump relays as these can handle higher loads then the original yellow relays. They are a bit expensive but I changed the ABS relay to make sure it does not stick and burn out the pump and in comparison this is a cheap way of safe guarding the abs pump.

Regards

Jos
 

·
Registered
1995-2002 Range Rover P38A
Joined
·
47 Posts
My theory on the fuse box is definitely that the one track is simply not wide enough (not enough copper) to carry the current. Have a look at the pics in the first post and the scorch marks neatly follow the path of the track on the other side of the board. My solution below was to solder a fairly heavy piece of silicone shielded wire in place of the track. So far the only problems have been my rather questionable soldering skills when joining the two halves of the board again, but the blowers have been 100%.

Electronics Electronic component Technology Electronic device Passive circuit component
 

·
Registered
Joined
·
4 Posts
this i would say is your biggest clue, resistance = heat, which equals more resistance which equals....and so on.
This is it in a nutshell!!!
Its not the relays that overheat (I'm talking about the operating coil here) its the current flow through dodgy connections. This can occur at two points, at the contacts on the PCB where the relay pins connect and at the contacts in the relay themselves.
It would appear that when there is damage to the PCB it happens as a result of poor contacts which then overheat the board. This in turn creates an even worse (higher resistance) connection and even more heat is generated in a spiraling out of control scenario to the point where the board is badly damaged. The contact points inside the relay can be damaged the same way. Often these two situations can occur together creating lots of heat and its resulting damage.

The idea of uprating the relay is good however you still rely on good contacts with the relay at the PCB. Directly soldering heavy gauge wires to the relay and PCB will ensure a very low resistance contact at these points and reduce the chance of overheating. Ask yourself this are all 40A rated relays equal? Can they really handle 40A continuously through the contacts without overheating or are they rated at 40A for a limited amount of time?

Uprated relays at say 50A have larger contact terminals (9.5mm) and different contact materials (AgNi) to reduce electrical resistance see here http://australia.rs-online.com/web/p/general-purpose-relay/5352564/. Unfortunately this relay wont plug and play but could be used to directly wire in.
 

·
LEGACY VENDOR
Joined
·
2,492 Posts
Guys, i plan to replace soon my fusebox that will have 15 years that year...

Replaced RL7 once since 12 years of ownership.
 

·
Registered
Joined
·
19 Posts
Discussion Starter · #18 ·
So far I am have heard that the fusebox copper strips are not up to the task of supporting the blower motor's electrical load. Also, one of the mechanics at my local Land Rover Stealer pointed out that the LH Blower motor has a longer primary wire than the RH blower due to its distance from the fusebox, and longer wire equals increased resistance, and increased resistance equals increased heat. These two statements are the most plausible things I have heard to date. When you combine this with the fact that a blower motor has the capability of burning out a fusebox which threatening the life of the $1500 BECM (not to mention the $300 for a new fusebox), it seems to me that the RL7 should be removed from the fusebox altogether. (Of course, those of you who want to keep shelling out $300 for new fuseboxes can do so.)

I am considering the following modifications:

1. locate the RL7 relay (maybe RL6, too) outside the main fusebox
2. wire the LH blower motor high power circuit directly to the externally mounted RL7 relay with a heavier wire (10ga or 8ga) bypassing the fusebox,
3. wire the remaining 3 wires from the fusebox RL7 socket to the externally mounted RL7 relay using a male socket created from an old relay
 

·
Registered
Joined
·
19 Posts
Discussion Starter · #19 ·
By the way, I forgot to mention that back when my truck was still under warranty, the Land Rover Stealer replaced BOTH the fusebox and the BECM, giving me a cock and bull story that "the fusebox can take out the BECM or vice versa, so we just replace both". obviously the fusebox is not up to task on RL7. Our trucks are getting older now, and it would be really ****ty to lose a BECM.
 

·
Premium Member
Joined
·
2,565 Posts
So far I am have heard that the fusebox copper strips are not up to the task of supporting the blower motor's electrical load. Also, one of the mechanics at my local Land Rover Stealer pointed out that the LH Blower motor has a longer primary wire than the RH blower due to its distance from the fusebox, and longer wire equals increased resistance, and increased resistance equals increased heat. These two statements are the most plausible things I have heard to date. When you combine this with the fact that a blower motor has the capability of burning out a fusebox which threatening the life of the $1500 BECM (not to mention the $300 for a new fusebox), it seems to me that the RL7 should be removed from the fusebox altogether. (Of course, those of you who want to keep shelling out $300 for new fuseboxes can do so.)

I am considering the following modifications:

1. locate the RL7 relay (maybe RL6, too) outside the main fusebox
2. wire the LH blower motor high power circuit directly to the externally mounted RL7 relay with a heavier wire (10ga or 8ga) bypassing the fusebox,
3. wire the remaining 3 wires from the fusebox RL7 socket to the externally mounted RL7 relay using a male socket created from an old relay
No mention of the duff left hand blower that's been in there for years even though its directly switched by RL7 :think:
 
1 - 20 of 49 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top