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Thursday, February 29, 2024

Doug's Domain

Doug Vetter, ATP/CFI

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Sunday, January 11, 2015

ZKW Ellipsoid Harness Adapter Fabrication

Over the last several weeks I've been researching the best way to connect the ZKW Euro Ellipsoid headlight assemblies to my US-spec car and acquiring the parts and tools to get the job done.

The ZKW assemblies come with a 4 pole twist-lock sealed electrical connector. The mating connector does not, of course, exist on the body harness of US spec cars so in order to connect the ellipsoids to the US spec harness a conversion cable is required. Where most people go wrong here is to assume the half-ass conversion cables sold by all the vendors of these headlights are acceptable for the application; let me assure you they are not, by virtue of the fact that they do not mate with the ZKW connector and properly seal it. The end result is usually complaints of fogging or condensation inside the headlight assembly. The issues, as always, include convenience and cost. The proper cable assemblies must be fabricated from scratch and they cost several times the $20 the vendors charge for their half-ass cables.

Fortunately, because the proper connectors (61 13 1 392 222) are used on the US cars to connect the engine harness to the mass airflow sensor, BMW provides the connectors in the US and at a reasonable price so I picked those up along with 8 pre-terminated pigtails (61 13 0 007 569). As I began to examine the mass airflow application more closely I realized the connector and wires exiting it were wrapped with a nice 90 degree rubber boot (12 52 1 713 508) that promised to dress up the connection and help it remain waterproof, so I decided to pick those up as well. That left the empty 9005/9006 (known in the BMW literature as HB3/HB4) mating shells, silicone seals and pins necessary to connect with the factory harness connectors.

I found some nice Japanese-made crimping and extraction tools online and those arrived within a week. Finding the shells turned out to be more difficult. Google was surprisingly useless in my quest. While I found a boatload of companies selling preterminated wiring harness adapters I had a hard time finding someone selling just the empty shells. I hit one site that showed pictures matching what I knew to be the correct connectors and part numbers so but I found the site design so pathetic I instinctually had second thoughts of doing business with them. And my opinion of this company wasn't exactly bolstered when I continued my search only to land at the same website through different domain names (a sleazy SEO marketing trick). I usually try not to judge a book by its cover but my experience has led me to accept a truism: where there's smoke, there's usually fire.

Unfortunately I don't always listen to my better judgment so I wound up ordering four of each type of connector from this company. The first order came in about a week but they screwed up the shipment and sent me (8) 9006 instead. I emailed them about the problem and specifically told them I needed the 9005 connector with two alignment / keying rails inside as shown on their website. I even sent them (at their request) a picture of the 8 connectors I received so there was no confusion about what I had received and what I needed.

A week later the replacement parts arrived but they turned out to be wrong as well. Instead of a proper keyed 9005 connector they sent me a generic part that lacked any keying. When I confronted them about this I attached the picture from their website showing the connector I needed and they said "the parts we sent you are correct...it's a universal connector good for 9005 and 9006 applications". They wound up offering an RMA to return them but as I'd already wasted far too much time on these morons I declined.

The universal connector technically fits either BMW harness connector, while the 9006 keyed connector with a single alignment rail will only fit one of the harness connectors. This means that I'll get the low/high beam circuit keying I require, albeit in a roundabout way (i.e. it will be impossible to mate both connectors to the harness simultaneously if I have them crossed), but the fact that the company misrepresented what they were selling irked me. I briefly considered going with another sealed and keyed connector made by Molex but that would have required chopping off the connectors on the harness and building up another adapter cable to allow backward compatibility with the DOT headlights in the event the Euro spec assemblies are damaged and I can't get another set imported. Call that the price of buying on the gray market!

The connector on the ZKW units is wired as follows:

One issue I had to address in the conversion was how to connect the single ground on the headlight connector to the ground in each of the vehicle harness connectors. While I suppose I could have connected only one of the grounds my alternate solution was simple enough -- an inline splice as close to the 4 pole connector as practical, fully soldered with extra flux to ensure the solder penetrated all of the wires and some heatshrink to protect the adjacent wires.

I used various sizes of heatshrink and flame-retardant nylon braid I had in stock to create the final cable and, after a last minute check of the polarity of the body harness connectors I sent the newly formed pins into the 9005/9006 connectors and called it complete. Time for one cable? 1.5 hours the first time through. I think I'll be able to do the next cable in less time...probably an hour.

Engine Vibration Worsens; Overhaul Planning Underway

The vibration at idle has gotten noticeably worse, to the point that my new door panels and some exterior panels occasionally vibrate noisily at idle. While the vibration isn't as strong at higher RPM I can feel a distinct lack of smoothness when I go wide open throttle now so I know this isn't just my imagination. The engine is giving ample warning that something in the bottom end is not right. As a result, I'm now making plans to pull the engine this spring, assuming it stays together that long.

I have considered several options at this point but a basic overhaul of the M52 in stock form is the most likely scenario. This would involve machining the block, a new oil pump (including safety-wiring the nut!), oversized pistons, and completely reworking the top end (machining the head, valves, guides and seals, new cams). The end result would likely be the equivalent of a new long block from BMW, i.e. a slight increase in compression ratio and fuel efficiency as a result, but running a 100% stock tune. No matter what I do, my top priority is to blueprint the engine so it runs as smoothly as it did when it was new.

With the engine out of the car I have a rare opportunity to replace the transmission so I intend to do that. The $60000 question: can I get both an engine overhaul and interior overhaul done this year to wrap up the major work on the car as originally planned? Your guess is as good as mine, but if I have any hope to succeed I'll need to start as early in the spring as possible and I may wind up having to outsource the engine swap to my local indy BMW technician, Don (a.k.a. Mr. M Car).

Mileage: 255435