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big110



Member Since: 02 Nov 2016
Location: Pinner
Posts: 365

 2014 Defender 110 Puma 2.2 SW Keswick Green
Help me understand Relays/Replacements Help
The backstory is I have a Heavy Duty Headlight loom kit from Red Bison which has been an outstanding bit of kit. When my high beams stopped working I narrowed it down to one of the two relays supplied with the Red Bison kit. Both relays on the kit read HID 40A/12VDC H4458-12VDC

I have been seeking a couple of replacements locally, and having limited knowledge of relays, I have simply been searching for the "H4458" number but not coming up with anything.

My question is when it comes to relays, is that just a part number and if I can source another relay with the same schematic on it, it will be the same?

The attached photos show the one that is broken under my hood, and one from amazon. The pictures/schematic on the relays looks the same but I just am not sure if that is good enough.

Thank you!



Click image to enlarge



Click image to enlarge
Post #1070681 2nd Jul 2025 2:13pm
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Martin
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Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6680

United Kingdom 2015 Defender 90 Puma 2.2 XS CSW Montalcino Red
Automotive relays are highly standardised - what you have fitted and the ones you have found on Amazon are generic Chinese-made low cost 40A relays.

There are however, two terminal layouts - called "Form A" and "Form B". Factory relays on a Defender are "Form B", from what I can find out, those H4458 relays are also Form B.

So, any 4 pin 40A Form B relay will be a replacement.

I would personally not fit a cheap Chinese-made relay as a replacement - but don't think you are UK based so won't link to UK suppliers.  1988 90 Td5 NAS soft top
2015 D90 XS SW
Post #1070685 2nd Jul 2025 3:22pm
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big110



Member Since: 02 Nov 2016
Location: Pinner
Posts: 365

 2014 Defender 110 Puma 2.2 SW Keswick Green
Thank you for that! I can source Bosch here in the states...any other brands that are quality I should look at?
Post #1070689 2nd Jul 2025 4:12pm
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Martin
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Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6680

United Kingdom 2015 Defender 90 Puma 2.2 XS CSW Montalcino Red
Bosch will be great. Just make sure they are "Form B": terminals 30 and 87 should be opposite each other, terminals 85 and 86 should be opposite each other:


Click image to enlarge
  1988 90 Td5 NAS soft top
2015 D90 XS SW
Post #1070690 2nd Jul 2025 4:15pm
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sako243



Member Since: 08 Jul 2014
Location: Wales
Posts: 1246

Wales 1994 Defender 110 300 Tdi CSW Alpine White
Just a word of warning about the Bison kit. It only takes the trigger feed from one headlight which means if there's an issue with the wiring to that light it takes out both. The factory LR wiring has four fuses with four feeds to the headlights which means if a wire breaks to a headlight then it only affects that headlight.

I had a rather disconcerting moment losing all headlights at 60mph alongside Loch Cluanie in the Highlands in a storm. Due to the alternator location I'd used the passenger side headlight on the 300Tdi which had chafed a wire in the loom as it went around the bulkhead corner.

Subsequently replaced with LED headlights and thus no need for the relays but it's gained the redundancy back of the original system. Ed
82 Hotspur Sandringham 6x6
95 Defender 110 300Tdi
Post #1070692 2nd Jul 2025 4:52pm
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big110



Member Since: 02 Nov 2016
Location: Pinner
Posts: 365

 2014 Defender 110 Puma 2.2 SW Keswick Green
Martin wrote:
Bosch will be great. Just make sure they are "Form B": terminals 30 and 87 should be opposite each other, terminals 85 and 86 should be opposite each other:


Click image to enlarge


Very grateful for that assist, martin!
Post #1070696 2nd Jul 2025 5:25pm
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big110



Member Since: 02 Nov 2016
Location: Pinner
Posts: 365

 2014 Defender 110 Puma 2.2 SW Keswick Green
sako243 wrote:
Just a word of warning about the Bison kit. It only takes the trigger feed from one headlight which means if there's an issue with the wiring to that light it takes out both. The factory LR wiring has four fuses with four feeds to the headlights which means if a wire breaks to a headlight then it only affects that headlight.

I had a rather disconcerting moment losing all headlights at 60mph alongside Loch Cluanie in the Highlands in a storm. Due to the alternator location I'd used the passenger side headlight on the 300Tdi which had chafed a wire in the loom as it went around the bulkhead corner.

Subsequently replaced with LED headlights and thus no need for the relays but it's gained the redundancy back of the original system.


Thats too bad. Red Bison has a great rep and I have not had issues before this relay issue. I do not prefer LED headlamps. I tested a number of manuafacturers and never found the light output of them to be what I was looking for. With this, I have been happy with uprated wiring and uprated bulbs in Hella housings. The redundancy is an interesting issue I will keep in mind but ultimatly happy to live with that risk. Bullbar and roof lamps for emergencies in my case Very Happy
Post #1070698 2nd Jul 2025 5:32pm
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big110



Member Since: 02 Nov 2016
Location: Pinner
Posts: 365

 2014 Defender 110 Puma 2.2 SW Keswick Green
Martin, this is a Hella relay which doesn't specify Form B, but it doesn't say its Form A either...
Look like a good replacement? Assume Hella is not Chinese made especially at that price..


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Post #1070704 2nd Jul 2025 7:18pm
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Martin
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Member Since: 02 Apr 2007
Location: Hook Norton
Posts: 6680

United Kingdom 2015 Defender 90 Puma 2.2 XS CSW Montalcino Red
From what I can see when checking the part number, it is Form B.

However it is made in China, but to Hella quality/spec.

I did say about avoiding the cheap Chinese (no-name) relays.  1988 90 Td5 NAS soft top
2015 D90 XS SW
Post #1070706 2nd Jul 2025 7:35pm
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big110



Member Since: 02 Nov 2016
Location: Pinner
Posts: 365

 2014 Defender 110 Puma 2.2 SW Keswick Green
so much for German engineering! back to the drawing board. Ill find a bosch version I am sure!
Post #1070710 2nd Jul 2025 8:15pm
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big110



Member Since: 02 Nov 2016
Location: Pinner
Posts: 365

 2014 Defender 110 Puma 2.2 SW Keswick Green
Martin wrote:
Automotive relays are highly standardised - what you have fitted and the ones you have found on Amazon are generic Chinese-made low cost 40A relays.

There are however, two terminal layouts - called "Form A" and "Form B". Factory relays on a Defender are "Form B", from what I can find out, those H4458 relays are also Form B.

So, any 4 pin 40A Form B relay will be a replacement.

I would personally not fit a cheap Chinese-made relay as a replacement - but don't think you are UK based so won't link to UK suppliers.


Martin, looks like I may need those UK suppliers links...coming up dry here! I can get this, made in Germany

https://industrialtecsupply.com/collection...in-germany
Post #1070918 6th Jul 2025 12:00am
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