How To: New Relay bank ground harness

[Bitsyncmaster]

The front relay bank has a “daisy chained” ground buss that seems to be causing a lot of problems as they age. What I think causes the problem is the double wire crimps were made without twisting the two wires into one group. So each wire got rolled to each side of the terminal and made weak crimp connections. Open barrel terminals are designed to have the rolled edges penetrate the wire at the center.

To make a new ground buss you will need:

1) 48.1 inches of 16 AWG black wire. I use AlpaWire type 3057 from a 1000 FT spool but any 300 volt 16 AWG preferably tinned.
2) 7 pn 42100-1 relay pin terminals. At Mouser these are 19 cents each
3) 1 Molex pn 19189-0015 butt splice terminal. At Mouser these are 19 cents each
4) 1.25” of .250” heat shrink tubing.

Tools needed are:

1) Wire cutters
2) Crimper for open barrel terminal
3) Crimper for closed barrel non insulated terminal
4) Heat gun for shrink tubing
5) Large paper clip to remove the old terminal from sockets.

The Butt terminal is rated for 10 AWG to 12 AWG and will just fit four 16 AWG wires in each end. You could use an insulated butt terminal but the one I specified is very heavy duty so the crimp should never have a problem. You can solder it but you would need a high wattage soldering gun to heat up the large mass of wires. I don’t recommend soldering.

Cut one wire each of the following lengths for one end.of the butt connector.
1) 6.4 inches
2) 5.2 inches
3) 4.5 inches
4) 2.7 inches

Strip one end of each and crimp into one end of the butt connector.

Now cut one wire each of the following lengths for the other end of the butt connector
1) 18 inches
2) 4.9 inches
3) 3.7 inches
4) 2.7 inches

Strip one end of each and crimp into the other end of the butt connector.

Slide your heat shrink tubing over the butt connector and shrink.

Now strip the seven shorter wire end of the wires and crimp on a new relay pin. Remove the OEM daisy chained pins for the front relay sockets (you will need to lift that relay bank and remove the relays). To remove the pins, I use a large paper clip to press the retaining nub while pushing and pulling the wire. Note there is one extra ground wire (center pin) on the fan relay socket that I do not use (not needed).

Grounds:
Fan Fail = pin 30
Fan Relay = pin 85
Dome unit = pin 86
Blower 4 = pin 85
Blower 3 = pin 85
High beam = pin 85
Low beam = pin 85

Cut the original ground wire that went to the low beam relay so you can connect the long 18 inch wire on my new ground buss to it. The 18 inch wire is long enough to let you make that butt splice back into the large group of wires to hide that splice.

I really don’t want to manufacture these and sell them. So this info is public for someone to do so if they wish.

[ALEXAKOS]

Thank you ELECTRODOC! :)

[Josh]

Thank you for this Dave. I will be integrating my MS relays into the existing fuse box so I will be doing just this. I have a few questions though.

I was planning on soldering. Everyone I have consulted said I need to solder to ensure a proper connection. But you say crimp. As the electronics guru of the forum I value your opinion! Can you explain why crimping is better for this application though? Also, do you have any suggestions for a crimping tool?

For what wire gauges are the safe currents? I tired to look this up online, but everyone gives a different answer. Interested in 18,16,14, and 12 gauge info. All wiring lengths will be mostly <1ft, but some up to 5ft as they are strung from the relay compartment to the engine through the bulkhead panel.

I look forward to your input!

[Bitsyncmaster]

Using the proper crimper with non-insulated terminals is a very good connection. Now is soldering after you crimp better? Yes. It's just that most people do not have the correct soldering tools or experience to get good soldering on very large wires. Getting a good solder joint requires the parts to be heated quickly so the wires do not get damaged with melted insulation and wicking of solder way up the wire. For this 8 wire butt splice a 200 watt soldering gun will do a good job. Or using a 150 watt soldering iron with a large tip also works good.

My crimper: photo attached works very good. Would be nice to have two of them since I'm constantly swapping from closed barrel to open barrel dies.

Wire gauge safety is usually not the issue. It's more to do with voltage drop. Also your limited with your choice of gauge by the terminals. You won't find a relay socket pin rated for wire larger than 12 AWG.

[Josh]

Using the proper crimper with non-insulated terminals is a very good connection. Now is soldering after you crimp better? Yes. It's just that most people do not have the correct soldering tools or experience to get good soldering on very large wires. Getting a good solder joint requires the parts to be heated quickly so the wires do not get damaged with melted insulation and wicking of solder way up the wire. For this 8 wire butt splice a 200 watt soldering gun will do a good job. Or using a 150 watt soldering iron with a large tip also works good.

My crimper: photo attached works very good. Would be nice to have two of them since I'm constantly swapping from closed barrel to open barrel dies.

Wire gauge safety is usually not the issue. It's more to do with voltage drop. Also your limited with your choice of gauge by the terminals. You won't find a relay socket pin rated for wire larger than 12 AWG.

Thanks for the reply Dave. I have a Weller 140W with a large end right now. I also have a butane pen soldering iron that gets much hotter, but I dont know the equivalent wattage. I just want to do it right the first time.

I found that crimper (just with one die, I dont use insulated terminals), its a tad expensive, but if it has served you well ill spend the extra money. I just had my cheap rivnut gun strip out and that was frustrating.

http://www.ebay.ca/itm/S-G-Tool-Aid-18930-Ratcheting-Terminal-Crimper-/190812084842?pt=LH_DefaultDomain_0&hash=item2c6d495a6a

[Bitsyncmaster]

Thanks for the reply Dave. I have a Weller 140W with a large end right now. I also have a butane pen soldering iron that gets much hotter, but I dont know the equivalent wattage. I just want to do it right the first time.

I found that crimper (just with one die, I dont use insulated terminals), its a tad expensive, but if it has served you well ill spend the extra money. I just had my cheap rivnut gun strip out and that was frustrating.

http://www.ebay.ca/itm/S-G-Tool-Aid-18930-Ratcheting-Terminal-Crimper-/190812084842?pt=LH_DefaultDomain_0&hash=item2c6d495a6a

Think I paid about $70 for my crimper. I have never used the insulated terminal dies and only use the two dies for Open barrel and closed barrel uninsulated terminal.

You 140 watt gun may work for that 8 wire 16 AWG crimp. You would have to try and see.

[Bitsyncmaster]

It looks like the bad relay grounds are going to become more and more of a problem. I’m thinking it already has caused cooling fan problems in the past and people are missing this intermittent problem. My solid state fan relay shows the bad ground problem quickly. Solid state relays need a good ground. Even running stock relays this ground problem will just not run your fans and then your only warning will be the temp gauge climbing.

So now I’m thinking of selling this relay ground) harness. The problem is, it’s not something anyone can make money doing. When you add shipping (boxing and USPS) costs and PayPal charges the price just seems to high for a “little wire”.

Attached is a photo of what can happen with my solid state fan relay.

[jmpdmc]

Dave,

If you bring some to DCS, I'll bet you could sell some. I think some of us would want to have one to protect our solid state RPM relays.



Jeff

[Bitsyncmaster]

Dave,

If you bring some to DCS, I'll bet you could sell some. I think some of us would want to have one to protect our solid state RPM relays.



Jeff

The RPM relay ground is shared with top bank of relays but it gets the ground first so not much trouble with that one. It's the bottom row with about 9 stock wiring double crimps. And the Fan relay is the last one on that daisy chain. What the problem is the way they double crimped the bare copper wires. Each wire got rolled under one side of the terminal. So the wire did not get a good tight crimp being 19 AWG. Also the bare copper (end of the wire) oxidizes to make it worse over time. That old copper is why I don't think you could solder them to fix the problem.

[jmpdmc]

Read your comment too fast and filled in RPM relay in my mind instead of fan relay. I do have the fan relay from you as well so I still think you should bring some to DCS.


Jeff

[Bitsyncmaster]

Read your comment too fast and filled in RPM relay in my mind instead of fan relay. I do have the fan relay from you as well so I still think you should bring some to DCS.


Jeff

I will try to have some at DCS. I already have a lot of inventory of my electronics ready for the show.

[250in5]

Dave,

When it melted all the ground wires (and it REALLY melted them), do you think it hurt the Fan Relay I just purchased? I know the cooling fans weren't kicking on (car was overheating as I tried to run home after pulling all the relays on that lower bank) or should I just simply pull all the wiring out and replace what is melted? I hate wiring and I have quite a little mess going in the compartment but that is the joy of owning a Delorean...learning to work on it! ;o)

Sorry to destroy your hard work...

~Korry

[Bitsyncmaster]

Dave,

When it melted all the ground wires (and it REALLY melted them), do you think it hurt the Fan Relay I just purchased? I know the cooling fans weren't kicking on (car was overheating as I tried to run home after pulling all the relays on that lower bank) or should I just simply pull all the wiring out and replace what is melted? I hate wiring and I have quite a little mess going in the compartment but that is the joy of owning a Delorean...learning to work on it! ;o)

Sorry to destroy your hard work...

~Korry

I will send you the new relay ground buss (black wires) and a new Fan Relay tomorrow.