S4 dash loom: make or buy?

[tonyabacus]

John
I seem to remember that British Auto Wire in the US is a supplier for Autosparks UK, so the harnesses will be the same, so worth talking to them.
Pity we are on opposite sides of the pond as I have a new Elan S4 Dash hrness that having installed it it suffered a partial burn out to the drivers side wondow wiring and a couple of other wires ( caused by someone whilst it was away having some other work done, dropping something across the window switch terminals). I decided that for me another new harness was the way to go, otherwise this may have suited your purposes for a small fee, but postage costs now are unlikely to make it worthwhile.
Tony

[JonB]

I’d be interested Tony - pm sent.

[JohnCh]

Thanks for all the info Stu. I did a little research on Advanced Auto Wire and it certainly looks promising. Two down sides are a power block on the large side, and someone this year mentioned it took 6 months to receive their loom. I'll give them a call today.

I haven't ordered anything from the UK for a couple of years but have heard postage fees have gone up. However, unless they have truly reached exorbitant levels, ordering from Autosparks rather than British Wiring still looks far more affordable. Converting at today's rate, the three harnesses from AS are $495 (sans VAT) whereas BS wants $950. If I am going to have any modifications done to those harnesses, I'd rather deal with the source.

I probably should start a new thread for this question, but after tilting the dash forward, I can't find where the dash loom grounds. I've read that loom should ground on the left side of the dash by the body, but unless it is tucked up behind the wiper motor, I don't see it. In fact, the only ground wire I found attached to the body/frame was the ground wire for a bulb on the tach that went to the bottom left dash mount in front of the center console. I'll do a more comprehensive search today, but is there another place it could be hiding?

[smo17003]

The dash loom grounds via one of the two body mount bolts on top of the tunnel. The bolts also locate the heater bracket.

Mike

[tonyabacus]

John
I think I quoted the wrong company previously, but here is a link to British Wiring who are based in Pennsylvania, which would save some postage costs. They are effectively the agents for Autosparks in the USA and so you are buying the same product either there or from the UK.

One point worth noting is that they now provide harnesses with the newer thin wall cables which are supposed to be the same as the originals but lighter. Having had a chat with Greg the technical guy at Autosparks, I believe you can still have a harness made with the thicker insulation, but then it may incur an additional cost. The second point is that the window harnesses could in my opinion do with a heavier gauge wire for both the supply and the earth.

Finally the earth you found at the bottom left hand corner of the dash on the tunnel is the main earth for that harnessHowever I have hooked up some additional earth wires to that same point.
Hope that clarifies
Tony

https://www.britishwiring.com/category-s/196.htm

[stugilmour]

Excellent John, happy to help. It is a daunting job, but I managed to get it done with no previous experience. I certainly would be better able to do the job a second time.

The Advance Auto Wiring power block is very large, although the other comparable systems seem to be similar. Did you notice they offer a smaller footprint model for a bit more dough? I couldn’t find the dimensions of the reduced size unit, so that would be a definite ask. First saw this tip on an MG forum. Also saw this on their order form:

Compact PowerBlock surcharge (in addition to the PowerBlock charge)

Also saw one build where a guy had broken the power block into component parts and mounted on the rear of the glovebox with the components facing inward. This is basically the approach I took in the Plus 2. Unfortunately I don’t know how much clearance you have in the Elan, but I have seen pictures on the forum where Elan owners took this approach, all be it with custom built up relay and fuse blocks. Having basically done this approach by extensively modifying a generic loom, these power block style looms have huge appeal because that is all the hard part done if you can figure out a mounting point.

I also saw references to unreliable delivery for this vendor. As a possible alternative, I saw a reference to a very similar system that offered the power block alone, or with an array of separate wire strands to simply assemble the loom yourself and connect the loom wires with a series of ring connectors. Can’t find it right now, but there were MG & Triumph guys who also liked that system and their supply situation may be better. Anyway, if I run across the reference again I will post a link.

I think the Advance systems are pretty similar whether they are building the loom for an MG, Triumph, or (who knew) a Lotus. Biggest differences are going to be ammeter/voltmeter/neither, headlight/sidelight switching details, electric or mechanical temperature gauge, temperature/fuel using 10v stabilized or 12v supply , and a few others. I think all of their looms are designed to expect one to use an aftermarket hazard flasher dash switch; I needed three relays to get the Plus 2 working with the stock switches. Also looks like you might need a couple of diodes to get the turn signal dash pilot light to work correctly; that’s what I had to do. The rest is perhaps not as easy to install as a stock loom, but can definitely be trimmed to fit really well.

The cool part I was thinking would be the Lotus Elan package would/should include the beauty documentation package they feature on their website for more popular models. With my generic loom my documentation and instruction package was basically a connection list and a few generic suggestions.

Anyway, will be interesting wgat you hear back regarding delivery.

Stu

[JohnCh]

Thanks Mike, that helped. I found it on the right lower bolt between the dash and bracket and hidden from earlier view as it came in from the left. There was also a white wire there I traced back to the blower fan. Is that normal for that ground wire to be white or was that orphaned and just happened to be back there? The blower did work when I checked it before starting on the dash.

I checked resistance from that black ground wire through the right window switch alternating between up/down and connecting to the appropriate wire to the motor each time. One wire was 2 ohms, the other was 3. That seems a little high for such a short run. I didn't have time to pull the ground from the switch and check if it's the wire or the switch, but it is more impetus to replace it all.

Speaking of which, Steve at Advanced Auto Wire called me back and we had a brief discussion. First, he seems like a good guy and the fact he got back to me same day is encouraging. Some specifics on his Elan wiring harness:

- He uses larger gauge wire for the windows, but does not include relays.
- All wire is thin wall GXL and he sticks to standard British wiring colors except for brown which he changes to yellow. Apparently Americans don't like brown. My Elan is yellow so I'm okay with that.
- All powerblocks are now the smaller size and approximately 7" x 7' x 2.5" (or 178mm x 178mm x 64mm in new money)
- Lead time is currently 8-10 weeks
- Price is $790

He also sent this wiring diagram which he said was fine to share here. I'm leaning heavily towards this option.

[Andy8421]

John,

If you are going to the trouble of installing a powerblock, I would have thought it worthwhile fusing the headlamps.

Referring to the diagram above, is there a reason why these have been left unfused?

Thanks,

Andy.

[JonB]

Good spot Andy

I was going to say the diagram is a thing of beauty... other comment, the PowerBlock looks quite expensive.

[JohnCh]

Good catch Andy, I'll ask Steve. Given both high and low beams have relays, would replacing those with fused relays be a simple fix?

[stugilmour]

Good catch Andy, I'll ask Steve. Given both high and low beams have relays, would replacing those with fused relays be a simple fix?

Possibly, but I haven’t seen fused relays that are “five pin double make and break” like the diagram calls for with both the low and high beam relays. Could be relatively easily changed by crimping both output wires together on the 87 pin and using the commonly available “four pin fused make and break” you are thinking of. Have to up the fuse value to handle both left and right headlight filaments. At any rate, the relay holders for four and five pin are the same, so pretty easy modification.

I recently used some fused make and break four pin relays for my ignition ECU project and noted the blade fuse holder seemed a bit loose. I made a holddown for the fuses to make sure they would stay in place. Not sure I would want them in this application.

Another option might be to add a fuse to the main power input yellow. Although a bit of a cludge, looking at the power block pictures either a couple of fly lead (hard to find in yellow, generally red) or crimp-able inline fuse holders (cut the existing yellow and crimp in place, beauty) could easily individually replace/fuse the two yellow wires from the power terminal bolt to input pin 30 on the relay blocks. That idea kinda assumes you are not adding another fuse/relay block; I think you are going to need another block to get some other Lotus switches to work, so important consideration as you are concerned about fitting everything into the car.

The cleanest option might be to add their dedicated headlight relay kit, which is essentially done the way I did it with four separate fuses on the output side of the relays. Interesting they don’t use double make and break in this loom; IIRC I did but it doesn’t really matter I suppose. More expense and packaging problems with this option though.

Headlight Relay Kit schematic from Advance Auto Wire

I wondered if they actually make the Lotus version with the headlights unfused. I thought I saw headlight fusing on the popular MGB, Triumph and generic looms, but I was mistaken. They all appear to be unfused. Pretty strange as they say you don’t need their headlight loom upgrade if you install the power block.

I would certainly want headlight fuses when I was finished though. Excellent catch. Will be interesting what they suggest as it can’t be the first time they have heard the question.

[RichardHawkins]

Talking of headlight circuits, I was concerned about the current drawn passing through some of the old switchgear on the flash function. I installed LED headlamps to reduce the load and improve the light.

Just a thought,

Richard Hawkins

[JohnCh]

I think you are going to need another block to get some other Lotus switches to work, so important consideration as you are concerned about fitting everything into the car.

Stu, what switches are you referring to? I don't see the headlamp pods switches in the schematic, but he did say on the phone those are included. I'll ask about this (unless I'm overlooking them?).

As an aside, all dash wiring is removed and labeled. As soon as I disconnect the coolant sensor bulb and thread it through the firewall and mass of wires on the other side, I can move the dash to the workbench. Bottom line, I'm definitely doing something this winter...

I have LED brake lights and will change the turn signals to LEDs as part of this conversion, but I'm not sure about doing the headlights. I agree with the load comment and when done correctly, they work well, but I never drive the car at night.

[stugilmour]

I don’t know the S4 loom in detail, so consider what I am saying more speculative than definitive. My direct experience is with a Plus 2 Federal, which undoubtedly has differences. Also completely new to this Advance loom.

That said, here is what I was thinking.

• I saw posts in MG / Triumph forums that the hazard flasher circuit requires the use of their supplied switch. Heaven knows if you can get whatever Lotus switch you have to work. In my case I used three relays to get mine to work, but my loom was a little different and uses only one flasher relay. Although Advance is a completely different circuit I am anticipating this will need a creative solution with some relays to work, but could be totally mistaken. Basically the dash switch (with or without a few relays to replicate the supplied switch) has to temporarily connect the left and right turn signals together while the Purple supplied hazard flasher relay is energized, and prevent interference/back feeding with the green supplied turn signals, which use the same bulb filaments, all independent of the position of the turn signal wand.
• The Plus 2 Federal uses microswitches installed in the vacuum pull switch rather than courtesy light door type switches in the pod, which I assume he is referring to? There are lots of variants of the headlight and sidelight switching, so not expecting this loom to necessarily be plug & play for any one model.
• My Federal sidelight circuit requires a latching relay to work with a flat intermittent dash switch. YMMV.
• I think you are planning electric pods? Minimum that requires a crossover control relay. In some cases a second relay may be required. Of course, this can be a completely different loom; the Spyder system also requires a control box to be mounted so is commonly put left or driver’s side.
• Not sure how many relays the Elan window lift circuit needs, but the Plus 2 required four. I used the smaller footprint micro-relays for these.
• I used relays for the heater fan, but that is probably a bit ridiculous. Others have serviced the NLA dash switches, but I didn’t have the guts for that. Anyway, two micro relays and the heater works.
• Used a power relay for the sidelights.
• I did see some posts talking about two diodes for the dash turn signal pilot light. That is how I did mine, but he uses a different flasher relay so might be plug and play.

Unfortunately the module size is going to limit mounting options. For comparison, the fuse and relay boxes I used were shorter than 7” and are a tight fit in the back of the glove box. Note my flasher relay is mounted remotely (accessed thru the ash tray), which probably allows a smaller footprint, and would potentially take up a bunch of room in the glovebox. Looking at the module picture I can see why the one guy decided to kinda pull it apart down the central wire valley to reconfigure things a bit. Just an option. Pretty easy to move a few yellow wires around with replacement crimps I suppose.

Relay box size H64 (2 1/2”) x W123 (~5”, really quite tight top and bottom of glove box) x D42mm (1 5/8”).

https://www.autoelectricsupplies.co.uk/p/relay-box

Cheers!

[JohnCh]

Thanks Stu. Looking at the schematic, the relay switch is definitely different, but given the Elan uses a small sliding switch under the dash on the bonnet release handle bracket, no one would know that I'm using a different switch down there.

The other switch that looks different is the headlamp switch. The Elan's has 4 terminals that feed:

panel lights & sidelights
dip switch
headlamp relays & ignition
Headlamp flasher relay

The AAW schematic shows a switch with 3 terminals that feed:

panel lights & sidelights
dip switch, which in turn feeds the headlamp relays
ignition

I'm assuming it's still an off/on/on switch and I don't mind losing the headlamp flasher but I'll also confirm there is no issue working with it or any of the other factory switches.

I made a mockup of the power block. It won't fit behind the glovebox, but there is so much leg room on the passenger side, a false floor that takes up 3" wouldn't be noticed. That might be an ideal location. Still easy to reach, centrally located, and out of sight.