How to Relay Control Module (RCM) Repair - (Mystery no Start)

[tighed1]

How to Relay Control Module (RCM) Repair - (Mystery no Start)

Click here to Go to post 120 for loaner RCM info
Thanks LGV-XFIRE!

This post is in response to the MANY occurrences of the "Mystery No Start" issue. Symptoms being car will die and/or will not restart but may restart after waiting for a while. Also, when attempting to start the engine all electronics work but the engine will not crank.

Hundreds have been spent "repairing" this problem by buying a new Relay Control Module (RCM) and paying for diagnostics, removal and installation.
Well I'm here to help save you some time, $$$ and aggravation cuz YOU will do the repair yer self!

This repair will require that you are able to properly operate a soldering iron. Beyond that it’s pretty easy.
Let’s get started (get it?)!


First four steps might look familiar cuz they come right out of the “Me so Horny” mod.

1. Disconnect the battery.
2. Remove the cover that contains the RCM and pull the RCM out.




3. Disconnect all plugs from the RCM.


4. Remove the protective cover from the RCM. Might take a little prying with small screwdrivers.

5. Inspect the rear of the RCM. Pay particular attention to the area in the yellow outline box located in the lower right hand portion of the photo.

Here are two examples of what you might see.
This is NYPD-Crossfire’s BAD RCM.

And now the close up.

By just slightly touching the center set of connections I was actually able to make and break the electrical connection. No wonder his car wouldn’t start.

Here is my still “good” RCM from the coupe.

As you can see the connections here are also VERY poor. It’s still working but looking like it does it wouldn’t be long before I too would have encountered the Mystery No Start issue.

• REPAIR

6. Time for the repair. Get yer soldering iron nice and hot and (one at a time) heat the joint and apply additional solder. Be sure that the joint gets hot enough to thoroughly heat the pins that are protruding through the board. The pins are pretty stout and if not heated enough you may get a cold solder joint and end up having a starting problem because of that.

Re-soldiered connections. Compare with the above photo. I think I'm safe now!

NOTE: Now would be a GREAT time to do the “Me so Horny” mod. Two deep cuts in the circuit board. Solder in two wires. That easy!
7. Put the protective cover back on the RCM.
8. Re-connected RCM.
9. Put the RCM back into the main box.
10. Install cover.
11. Connect battery.

Yer Done!

[tighed1]

Anyone that would like me to repair their RCM PM me for my address and let me know if you would like the "Me so Horny" mod applied.

At this point I'd like to ask that you toss 10 bucks in with the RCM when you mail it so I don't have to pay postage to get it back to you. I'll keep the change to buy a beer for the repair!

All you folks in the cold areas that store your cars for the winter, now would be a perfect time to get someone (doesn't have to be me) to fix yer RCM.

[pizzaguy]

You get an A+++ for photography.

So, the module just sits in there? Nothing actually holding it in place? No wonder the solder cracks, vibration does it.

(I KNEW that it wasn't hot enough to melt the solder).

[Stogey]

Major Kudo's !!! Wish I would have had this a year ago when I replaced mine !!!

[oledoc2u]

those are some poor looking solder joints...guess I should take mine out and check it...

[onehundred80]

Great job tighed1, I was wondering about the missing pics, so I looked at your gallery and there they were. When I got back they were in place.
Its amazing that there are so many badly soldered joints, are these done by machine or are they of such low quantity that they are done by hand? If they are done by hand then some of these solderers need to take soldering 101.

An added thought, better add that the soldering iron be about the right size, not to big and not too small. The solder should be resin cored solder not acid cored or plumbers solder as we would not want the acid to start ruining the job slowly.

[pizzaguy]

180:

I see this all the time in both Motorola and competitive equipment: they use the MINIMUM amount of solder to build the assembly.

They teach you to "not depend on solder for physical strength, always tie down and secure connections, boards, etc."
Which is stupid, cause....They also teach you to use the minimum amount of solder that will "do the job".

I spend a LOT of time resoldering broken connections in radios, sirens, lighting control boxes and other crap we put into police and fire vehicles. I must say, some stuff STILL comes back in a few years, no matter how much solder I use or how hard I try to "make it right".

But the fact remains, if you flow enough on there like in tight's "Me So Horny" modification pictures - you WILL have less trouble.

[tighed1]

Yo Mods.
Is this a Sticky?

[pizzaguy]

You mods.

BLOW MY FIRST POST AWAY!

[onehundred80]

I am assuming that any of the soldered joints may be suspect or is this spot the most likely point of failure?
If so this should be stated more positively in your post, otherwise people will just look at that one spot, add a bit of solder there and the car will still not start.
Great job, I am not being picky just trying to save later questions and assumptions that are not totally correct.

[tighed1]

Originally Posted by onehundred80

I am assuming that any of the soldered joints may be suspect or is this spot the most likely point of failure?

Originally Posted by onehundred80

If so this should be stated more positively in your post, otherwise people will just look at that one spot, add a bit of solder there and the car will still not start.
Great job, I am not being picky just trying to save later questions and assumptions that are not totally correct.

I JUST now checked my roadster's RCM and it too has the exact same poor connections at the stated joints.
When I received NYPD-Crossfire's known bad RCM I tested the circuit paths through each of the five relays. It wasn't till the last relay (of course) that I encountered a problem (open). I then closely inspected all of the connections with a jewelers monocle and that is when I found the bad joints.
Out of the three RCM's that I have checked all had poor joints at the stated location and no where else. This is not to say other joints might not be bad and since you have the RCM out you might as well inspect all of it.

But as far as the Mystery no Start issue goes I am pretty confident that THIS is the cause and solution.

[ZERACER]

Sticky Please !!!

[magneticred]

This is one of the best DIYs I have ever seen. Definitely sticky material.

[GDC-SRT]

tighed1,

Fabulous job with photos and all
"A+"

[hcarter]

ONE OF THE BEST FYI "S Thanks !!!

[Kurts]

Originally Posted by pizzaguy

180:

I see this all the time in both Motorola and competitive equipment: they use the MINIMUM amount of solder to build the assembly.

They teach you to "not depend on solder for physical strength, always tie down and secure connections, boards, etc."
Which is stupid, cause....They also teach you to use the minimum amount of solder that will "do the job".

I spend a LOT of time resoldering broken connections in radios, sirens, lighting control boxes and other crap we put into police and fire vehicles. I must say, some stuff STILL comes back in a few years, no matter how much solder I use or how hard I try to "make it right".

But the fact remains, if you flow enough on there like in tight's "Me So Horny" modification pictures - you WILL have less trouble.

Ain't THAT the truth, Mark!
As you, I've lost count as to how many boards I've had to resolder because of lousy factory jobs.

180 - ALL modern PCB's are soldered by machines. Waaaaay to costly to do it by hand.

Tighed - EXCELLENT post. I can now see all of us out here yanking our RCM's for a little preventive maintenance!

THANKS!!!

[waldig]

Good kill. I offer up a WOODY award for that one.

Didnt wanna stiff you, good work.

Annular solder cracks are often due to thermal expansion and contraction stressing the minimal solder joints.

Me I make nice round balls of solder, for strength.

Woody

[pizzaguy]

Originally Posted by Kurts

I can now see all of us out here yanking our RCM's for a little preventive maintenance!

I was thinking we could have an "RCM Preventative Maintenance Party" at the lodge.

We need a gun with new tip, solder, few hand tools for keeping the tip nuts tight, a smoke vacuum with filter (if we are doing this indoors) and maybe a 100 foot cord (if we are doing this outside).

I have all the above in my bag of tricks, and think I can squeeze it all in the trunk, since it looks like top-up weather (due to cold, if not rain).

What do you all think? Could keep us busy - or should I save the room for my costume for saturday night?

[tighed1]

I was wondering if the joints might see too much heat or if it's just a common defect. So far three out of three have had bad joints.

Folks. Might want to take a look at your RCM's before you get stranded! Don't say you weren't warned!

One of these days after a drive I'll remove the protective cover and check the temperture of the area of failure to see if it is higher than the rest of the board.

[MannyTwoTwo]

I concur about the location of the solder points. Those are the same three I re-flowed over two months ago and no more problems.

Great job tighed1.