When building a wiring loom, there are often multiple ways to accomplish the same job.
That is definitely true when comparing Molex parallel splices and Raychem D-609 splices.
Both are legitimate crimp splice options used in professional wiring, but they are not usually chosen for the exact same reason.
In real-world use, the biggest difference often comes down to one thing:
👉 how small you need the splice to be
If you do not need the splice to be as compact as a D-609, Molex parallel splices are a very good and perfectly acceptable alternative.
If the splice needs to stay as small as possible, the Raychem D-609 is usually the better choice.
What Is a Molex Parallel Splice?
Molex parallel splices are a strong crimp splice option, and the sizes we commonly use are:
- 19207-0001 → 22–18 AWG
- 19205-0001 → 16–14 AWG
- 19205-0003 → 12–10 AWG
- 19205-0004 → 8 AWG
These are a good option when you do not need the splice to be as compact as a D-609.
They are commonly useful in:
- general automotive wiring
- larger branch splices
- power wiring
- applications where a little more splice size is acceptable
In many situations, they are a practical and reliable solution.
What Is a Raychem D-609 Splice?
The Raychem D-609 splice family is commonly used in higher-end motorsport and mil-spec style harnesses.
The sizes we most commonly use are:
- D-609-03 → 20–26 AWG
- D-609-04 → 16–20 AWG
- D-609-05 → 12–16 AWG
These splices are popular in professional loom building because they are compact and work well when packaging space is limited.
That makes them especially useful in:
- tight harness branches
- motorsport looms
- compact service loops
- areas where you want the splice footprint to stay as small as possible
The Main Difference in Real-World Use
In practice, the primary difference usually comes down to size requirement.
If you do not need the splice to be as small as possible:
👉 Molex parallel splices are an acceptable alternative
If you need the splice to stay as compact as possible:
👉 Raychem D-609 is usually the better choice
That is really the simplest way to think about it.
This is less about one being universally better than the other, and more about:
- available space
- packaging requirements
- loom style
- the type of build you are doing
When Molex Parallel Splices Make Sense
Molex parallel splices make a lot of sense when:
- you have a little more room
- the splice does not need to be extremely compact
- you are working with larger wire sizes
- you want a practical and reliable splice solution
- the loom does not need to follow a tighter motorsport-style packaging standard
They are a very usable option and work well when the extra size is not a problem.
When D-609 Usually Makes More Sense
Raychem D-609 tends to make more sense when:
- harness packaging is tight
- you want the splice to stay as compact as possible
- you are building a high-end motorsport loom
- you are already using Raychem / mil-spec style materials
- appearance and compactness matter
In those situations, splice size becomes a major factor.
Why Builders Compare Them
People often compare these two splice styles because they can both solve a similar problem in a loom, but they reflect different priorities.
A Molex parallel splice is often chosen when:
- size is less critical
- practicality matters
- a slightly larger splice is acceptable
A D-609 is often chosen when:
- compact packaging matters
- loom finish matters
- higher-end harness standards matter
That is why the comparison is useful.
Why I Usually Avoid V-Crimp / “Taco” Style Splices
Another common splice style you will see is the V-crimp or “taco” style splice.
These are often used because they are:
- inexpensive
- easy to find
- quick to install
But in my opinion, they are usually an inferior option compared to a proper Molex parallel splice or Raychem D-609.
Why I Don’t Like Them as Much
The biggest issue is that they generally do not offer the same level of:
- mechanical strength
- consistency
- compactness
- overall finished quality
In many cases, V-crimp or taco splices can feel more like a compromise than a proper long-term solution.
Common Problems with Taco-Style Splices
Some of the drawbacks include:
- less controlled crimp shape
- less professional finished appearance
- more variation depending on tooling and technique
- bulkier or less refined results in the harness
- generally not the splice style I would choose for a higher-end loom
For basic applications, they may still work. But for a cleaner, more professional harness, I generally prefer a better splice solution.
Why They Feel Inferior in a High-End Loom
When you are building a higher-quality harness, details matter.
A splice should not just “work” — it should also:
- package well
- look clean
- be consistent
- fit the overall standard of the loom
That is where taco-style splices usually fall short for me.
If I do not need the splice to be extremely compact, I would rather use a Molex parallel splice.
If I need the splice to stay as small as possible, I would rather use a Raychem D-609.
That leaves very few situations where I personally prefer a V-crimp / taco-style splice.
Crimp Quality Still Matters Most
No matter which splice you use, the biggest issue is still usually not the splice itself.
It is:
- incorrect tooling
- poor crimp quality
- bad wire prep
- inconsistent technique
A better splice will not fix a bad crimp.
So whichever route you choose, make sure:
- the wire size is correct
- the tooling is correct
- the crimp is consistent
- the application makes sense
Which One Should You Use?
A simple way to decide is:
Use Molex parallel splices if:
- you do not need the splice to be that small
- you have more available space
- you want a good practical alternative across multiple wire sizes
Use Raychem D-609 if:
- you need the splice to stay as small as possible
- you are building a tighter, cleaner, more compact loom
- you are working in a motorsport or mil-spec style harness environment
That is usually the real-world decision.
Final Thoughts
Molex parallel splices and Raychem D-609 splices are both useful options, but they are typically chosen for different reasons.
In many cases, the primary difference in usage comes down to how small the splice needs to be.
If you do not need the splice to be that small, Molex parallel splices are a perfectly acceptable alternative.
If compactness matters most, D-609 usually wins.
And for me, that is also why I rarely prefer V-crimp or taco-style splices on a higher-end harness.
That makes the decision much more about packaging and loom style than about right versus wrong.
Need Help Choosing the Right Splice?
If you are not sure which splice makes the most sense for your application, we are happy to help.
📧 sales@ksvlooms.com
📞 1-888-725-5711