thatbus
Well-known member
- Joined
- May 1, 2022
- Member Number
- 5129
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- 191
Currently building the wiring harnesses for my 4x4 bus... I chose to use Amphenol AT series and Deutsch DT series, for several reasons I'll get to.
I work on used school buses; I do a mix of metal fabrication/welding thanks to the amount of salt we use on our roads up here... and a lot of electrical work. I source all their electrical components, too. We have the largest contract for purchasing and selling used buses in Canada and as such, are refurbishing or modifying many buses each week before sending them off to new customers. We get buses in all sorts of conditions, states of neglect, with all sorts of powertrains, and all sorts of chassis. I get to see pretty much every electrical connector used from the 80's thru the 2010's that you could imagine.
Metripack:
Nearly every bus built in the last decade, especially late model GMC van-chassis short buses, use lots of Metri-pack connectors. The housings don't separate easily by accident, since the tab must be lifted not pushed. However, not as easy to remove with gloves. They self-clean upon removal fairly well. Finnicky to remove contacts though.
"Normal" 150 or 280 series or "pull-to-seat 150.2" Metri-pack are common here. In general, I am a big fan of these connectors but they're hard to find at acceptable prices. They are compatible with AMP Superseal 1.5 (usually for a way better price).
One thing I find very annoying about Metri-pack is that their wire-to-sensor connectors are completely different even though they look identical to wire-to-wire. Those are 150.2 series; "pull-to-seat". Different contacts, subtly different keyed housings. I see no distinct advantage; if you are relying on their design to prevent pullout, you're doing something wrong and need better strain relief anyways.
Only had a few 150/280 connectors fail; aside from a pinched seal (installer error I suspect) failures were always from the locking tab on 150 GT-series connectors cracking and the connector working loose. These are often used for fuel pump/sender connections, and they're horrible for that purpose; the locking tab fills with dirt very quickly and they're hard to open without breaking. 150, 150.2, 280 connectors don't have this issue.
More than anything, this is an incrimination of the serviceability of all heavily shrouded connector designs like the Metri-pack GT series in dirty environments. Deutsch, Amphenol A, "normal" Metripack, or AMP Superseal would all be superior for those environments, in my opinion. Great in theory, serviceability nightmare in dirty environments. An example of how these heavily shrouded connectors often fail me - housing/locking tabs get filled with dirt, tech struggles to remove it and it gets broken, or maybe they can get it off, but dirt inside prevents the latch from engaging when the connector is reinstalled, so it falls out eventually:
In short, I would recommend them, provided you can find them for a good price. I would also suggest stocking up on Metri-pack 150.2 if you ever use GM sensors/sending units/anything with an overmolded socket. Go to the junkyard, cut some off (the grey ones with blue seals and black ones with green seals are keyed different) and buy the crimp contacts for cheap.
Weatherpack:
I get a lot of these on older GMC van chassis short buses and 90's/2000's International 3800's. Relatively speaking the most failure-prone connectors, though most buses have no issues. Typical failures: Mechanical damage; they're big get in the way in tight spaces. Rear seals work loose or crack. Water intrusion is a common problem. Wires break where they enter the housing, though I'm not sure if that's thanks to bad strain relief, or simply owing to their age - they're the oldest connectors aside from the few Packard 56 series I see (lol). These connectors aren't bad, but they're finnicky to work with and for the same money you can probably get something better. I wouldn't recommend them. I always replace Weatherpak with AMP Superseal 1.5, Amphenol AT, or whatever is dominant on the chassis.
Deutsch/Amphenol:
I see these on all the CAT-engine buses we get and certain Bluebirds that use AHDM circular connectors. Only one near-failure (with a DT connector). They're fantastic.
You can use a couple contact sizes for everything from 22 AWG to 14 AWG. I see everyone suggest the machined barrel contacts which take a Daniels-type crimper. Personally, I have never seen the need for these aside from increased productivity. I have only used stamped contacts and have never had an issue provided a good tool is used. I use an ENGINEER PA-21 for them; made in Japan, well-made too. Only cost me $60, bit slow to use but it makes perfect crimps in D-series and A-series contacts, Metri-pack 150, 280, 150.2, and tiny JST XH/Molex connectors.
I buy AT60-16-0622 and AT62-16-0677 in bulk to cover 99% of my needs; 20 AWG to 16 AWG in a single contact. There is some compatibility with Mil-spec D38999 contacts too; you can get alumel and chromel thermocouple contacts that, while not intended, will fit any #16 or #20 Deutsch or Amphenol connector housing.
Housings are great; self-cleaning upon removal, can't fill with dirt in a way that prevents removal, locking tab is easy to press with gloves on, but cannot come loose from being pushed against a surface (it must be pushed below two bumps in the housing), and the seals are integral to the housing. No delicate seal you have to crimp on the wire. If you screw up a contact position, a tiny flathead screwdriver can be used to press a detent within the housing and get it out. No special tools except with circular housings. Only one near-failure; oil working past a Deutsch DT seal on a CAT C7. The engine was spraying hot oil from a compromised ORB fitting, so it was soaking for months.
Not technically a failure but the connector was "wet" inside and I doubt most other connectors would fare better.
The last bus I worked on used Amphenol AHDP connectors only a foot off the ground, at the front of the bus. Rough environment. No water intrusion, no damage. They held up great.
In general I am a fan of CAT's wiring harness design. They use a PVC-coated nylon yarn. This stuff is very durable, though you need a harness braiding machine to use it, but Techflex "OVR braid" is the same material in a "slide on" format.
Finally; most failures I deal with aren't at the connectors, rather, in two places: Unsealed relay and fuse panel corrosion, and where a loom stops and wires enter a connector. Wires get nicked, touch hot things, or flex and crack over time from poor strain relief. However, many Deutsch/Amphenol connectors come with ample room for heatshrink. No need to buy expensive backshells. I get all my connectors in bulk from Newark Avnet; cheapest place in Canada for them.
I work on used school buses; I do a mix of metal fabrication/welding thanks to the amount of salt we use on our roads up here... and a lot of electrical work. I source all their electrical components, too. We have the largest contract for purchasing and selling used buses in Canada and as such, are refurbishing or modifying many buses each week before sending them off to new customers. We get buses in all sorts of conditions, states of neglect, with all sorts of powertrains, and all sorts of chassis. I get to see pretty much every electrical connector used from the 80's thru the 2010's that you could imagine.
Metripack:
Nearly every bus built in the last decade, especially late model GMC van-chassis short buses, use lots of Metri-pack connectors. The housings don't separate easily by accident, since the tab must be lifted not pushed. However, not as easy to remove with gloves. They self-clean upon removal fairly well. Finnicky to remove contacts though.
"Normal" 150 or 280 series or "pull-to-seat 150.2" Metri-pack are common here. In general, I am a big fan of these connectors but they're hard to find at acceptable prices. They are compatible with AMP Superseal 1.5 (usually for a way better price).
One thing I find very annoying about Metri-pack is that their wire-to-sensor connectors are completely different even though they look identical to wire-to-wire. Those are 150.2 series; "pull-to-seat". Different contacts, subtly different keyed housings. I see no distinct advantage; if you are relying on their design to prevent pullout, you're doing something wrong and need better strain relief anyways.
Only had a few 150/280 connectors fail; aside from a pinched seal (installer error I suspect) failures were always from the locking tab on 150 GT-series connectors cracking and the connector working loose. These are often used for fuel pump/sender connections, and they're horrible for that purpose; the locking tab fills with dirt very quickly and they're hard to open without breaking. 150, 150.2, 280 connectors don't have this issue.
More than anything, this is an incrimination of the serviceability of all heavily shrouded connector designs like the Metri-pack GT series in dirty environments. Deutsch, Amphenol A, "normal" Metripack, or AMP Superseal would all be superior for those environments, in my opinion. Great in theory, serviceability nightmare in dirty environments. An example of how these heavily shrouded connectors often fail me - housing/locking tabs get filled with dirt, tech struggles to remove it and it gets broken, or maybe they can get it off, but dirt inside prevents the latch from engaging when the connector is reinstalled, so it falls out eventually:
In short, I would recommend them, provided you can find them for a good price. I would also suggest stocking up on Metri-pack 150.2 if you ever use GM sensors/sending units/anything with an overmolded socket. Go to the junkyard, cut some off (the grey ones with blue seals and black ones with green seals are keyed different) and buy the crimp contacts for cheap.
Weatherpack:
I get a lot of these on older GMC van chassis short buses and 90's/2000's International 3800's. Relatively speaking the most failure-prone connectors, though most buses have no issues. Typical failures: Mechanical damage; they're big get in the way in tight spaces. Rear seals work loose or crack. Water intrusion is a common problem. Wires break where they enter the housing, though I'm not sure if that's thanks to bad strain relief, or simply owing to their age - they're the oldest connectors aside from the few Packard 56 series I see (lol). These connectors aren't bad, but they're finnicky to work with and for the same money you can probably get something better. I wouldn't recommend them. I always replace Weatherpak with AMP Superseal 1.5, Amphenol AT, or whatever is dominant on the chassis.
Deutsch/Amphenol:
I see these on all the CAT-engine buses we get and certain Bluebirds that use AHDM circular connectors. Only one near-failure (with a DT connector). They're fantastic.
You can use a couple contact sizes for everything from 22 AWG to 14 AWG. I see everyone suggest the machined barrel contacts which take a Daniels-type crimper. Personally, I have never seen the need for these aside from increased productivity. I have only used stamped contacts and have never had an issue provided a good tool is used. I use an ENGINEER PA-21 for them; made in Japan, well-made too. Only cost me $60, bit slow to use but it makes perfect crimps in D-series and A-series contacts, Metri-pack 150, 280, 150.2, and tiny JST XH/Molex connectors.
I buy AT60-16-0622 and AT62-16-0677 in bulk to cover 99% of my needs; 20 AWG to 16 AWG in a single contact. There is some compatibility with Mil-spec D38999 contacts too; you can get alumel and chromel thermocouple contacts that, while not intended, will fit any #16 or #20 Deutsch or Amphenol connector housing.
Housings are great; self-cleaning upon removal, can't fill with dirt in a way that prevents removal, locking tab is easy to press with gloves on, but cannot come loose from being pushed against a surface (it must be pushed below two bumps in the housing), and the seals are integral to the housing. No delicate seal you have to crimp on the wire. If you screw up a contact position, a tiny flathead screwdriver can be used to press a detent within the housing and get it out. No special tools except with circular housings. Only one near-failure; oil working past a Deutsch DT seal on a CAT C7. The engine was spraying hot oil from a compromised ORB fitting, so it was soaking for months.
Not technically a failure but the connector was "wet" inside and I doubt most other connectors would fare better.
The last bus I worked on used Amphenol AHDP connectors only a foot off the ground, at the front of the bus. Rough environment. No water intrusion, no damage. They held up great.
In general I am a fan of CAT's wiring harness design. They use a PVC-coated nylon yarn. This stuff is very durable, though you need a harness braiding machine to use it, but Techflex "OVR braid" is the same material in a "slide on" format.
Finally; most failures I deal with aren't at the connectors, rather, in two places: Unsealed relay and fuse panel corrosion, and where a loom stops and wires enter a connector. Wires get nicked, touch hot things, or flex and crack over time from poor strain relief. However, many Deutsch/Amphenol connectors come with ample room for heatshrink. No need to buy expensive backshells. I get all my connectors in bulk from Newark Avnet; cheapest place in Canada for them.
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