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EEC Power Relay Problem

10K views 31 replies 4 participants last post by  waltman 
#1 ·
89 Bronco fullsize, 302 automatic.

My EEC power relay got fried about 10 days ago, I replaced it and then about two hours ago, it fried again. Anyone have any ideas as to what could be causing this, where I should look, and what I should do to fix this and prevent it from happening again. $25 every ten days for a relay just isn't going to work for me.

Also with my ignition off, I have 12 volts at the yellow wire that goes to the fuesable link. Should I not have zero volts with the ignition off? What could cause this?


PS. I f_cken hate electrical problems. I suck at it.
 
#2 ·
Sweet. I just spent a few days with my EEC relay. :laugh

The yellow wire is constant, and the fusible link is on the hot side of the starter solenoid, so having 12v all the time is correct.

The relay gets constant 12v, ground, ignition 12v and the signal from the computer.

Can fusible link go bad? Can the ignition 12v be doing something?

Here are the EVTM's Ryan (FireGuy) posted for me when I was fixing mine:
http://fordfuelinjection.com/?p=36



 
#3 ·
The fusible link can't be bad since I have the constant 12 volts so that should at least rule that out. I will check out Ryans site and see what i can come with, in the mean time, I'm going to the wreckers tomorrow to pick up a couple of spare relays, thanks Chris.
 
#5 ·
Aren't they just regular ol' 30 amp 12 v relays? I pull mine occasionally when I'm away on the highway and they look no different than the ones CT sells.. Maybe try splicing in a 25 amp fuse holder instead of the fusible link so it cooks the fuse instead of the relay. LR
 
#8 ·
Yes, a 30 amp relay will act just like a fuse if too much current passes through, it simply "pops" and is done. This almost sounds a little deeper though, maybe a TFI module or the sort..? LR
 
#9 ·
I think it's my fusable link.
I broke open my relays. The first one that fried, the factory one, was very corroded inside. The new one I just bought looked fine, so I plugged it back in and it worked. So when I plugged it back in this morning to see what would happen, the fusable link must have been set off at the time.

Anyways, I hooked up a voltmeter to the red wire that only has power when the ignition is on and while the motor was running, the volts started at 14+ volts and after several minutes dropped down to 5 volts and that is when the truck dies. Several minutes later, the relay clicks and the volts go back up to battery voltage.

So I guess all I have to do is get a new fusable link. cool

LR is it in fact 30 amps? I'm going to see if I can find it in my manual, but besides the words fusable link on the schematic, there is no actual value for it.
 
#11 ·
No, the relays are typically rated for 30 amps in that size. The circuit's probably fused at 20 amps or the sort. Any manual with a wiring diagram should specify by colour what the values are of each fusible link, and albeit I don't know where they would be, my best guess would be coming off the starter relay or buried somewhere in the wire loom under the hood. Lucky I haven't had to mess with any besides a couple in my '87 Ranger, and it was an absolute whore to find and fix.. LR
 
#12 ·
I found what I believe to be the fusable link and I checked the voltage at both sides of it before and after it dies and the power drop to 5 volts is the same. The wiring is headed towards the engine so I will start there next.

Wouls the engine cooling temp sensor have anything to do with this and or the air intake sensor, because they both came up when checking for codes.
I am about to check them and see what is going on there.

From what I've read, a fusable link will not reset itself, but the fact that it doesn't actually drop to zero volts has me wondering what that is all about.
 
#13 ·
I just checked the resitance and both were around 20 ohms, if that means anything. Then I checked the voltage for both, and they read about 1.25 volts and should be 5 volts. The manual says it should read 5 volts. So....it's my computer?
 
#15 ·
Wow, I do a little work and look at all the action. :laugh

The links are about 6-8" from the hot side of the starter solenoid. I have 4 of them on my '85 (EEC, F/Pump, ? and ?).

That's all I can tell you. I hope the EEC fixes it.



 
#16 ·
This is what I found and thought was a fusable link (the red wires with the black around it.)


is it?

If the computer doesn't fix it, I will be checking the links near the starter.

Chris, what are your thoughts on the voltage going from battery voltage to 5 volts when the engine dies?
From what I've posted, do you think I am right about the PCM or am I just throwing money at it?

By the way, I called Midway tire and the guy I talked to suggested I just buy a used PCM since the rate to diagnose the problem could easily surpass the $140 I spent for the new computer and it could very well be the PCM.
 
#18 ·
I wouldn't mind the pic Chris, but I don't think that is my problem. When I got the rebuilt computer, I installed it and before starting it, I checked the voltage of both those sensors and it was at 41/2 volts....yeah. I start it up and it reved for 2 seconds, then dropped to 700 RPM and boy did it run smooth. I've had a rescent lope in the idle like the IAC was acting up. BUT, then about 3 seconds later it died. I checked the voltage for the sensors and they were .09 for both and the EEC relay was reading 1.98 volts.......AAAAAAAAAAAAAAAAAAAAAA!!!!!!!!!

Long story short, they sent me the wrong computer. The box had the right number but the computer did not. So now I have to wait until about noon tomorrow to see if all will be OK.
 
#20 ·
I wouldn't mind the pic Chris, but I don't think that is my problem.
Ya, the more we talk about the link, the more I can't help but thinking that I've never seen them do anything but blow and kill all power.

I might be seeing a few of my "mechanic" buddy's on the weekend, so if you don't figure it out by then, I'll run it by them and see what they say.



 
#19 ·
I can't find anything about the voltage, but I do see that you should have a white/light blue wire that goes from the EEC relay to the to the ignition coil, and there is a (blue) fusible link on it.

The fusible link that goes to the starter solenoid shows as being blue, 20ga.

Here are a couple pics of my harness with the link's:







The link is under the electrical tape in the first picture.

They shouldn't be hard to miss, as Ford connects them to the regular wire with a big injection molded piece.



 
#25 ·
Where is the fusable link?


Is this it? (same cluster of wires but connected to 1 thicker wire at the sarter relay and I checked for resistance from the relay terminal to 3 random wires from the cluster after the splice and have zero resistance)


Is it normal for me to get a reading like this across my relay with the ignition off (the meter is set to 20 ohms)


the ignition is on here (both instances the battery is not connected)


I am so pissed off right now that I am actually calm.
 
#26 ·
Anybody know about electrical issues with vehicles. I will pay for your time




That one red ignition wire going to the EEC relay is staying at a constant 5 volts, where as before it would go up to 12 volts. Should it be 12 or 5 volts? I'm at my wits end and running out of ideas.
 
#28 ·
It WAS starting then dying after a minute or so, then rest and able to run again, now it wont even run. I'm not sure what a fusible link is, but the ones I did check (assuming they were the ones, they had battery voltage going through them)
I am in Newton and would love it if you came by to help.
 
#29 ·





Yes, it's true, I fixed it!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I checked the voltage for all the wires at my ignition switch and everything stayed the same, before and after it dies. I was then in the process of looking at my alarm that I no longer use due to me painting over the password for it years ago (the company doesn't exist anymore as well) but it is still hooked up. While I was checking the voltage at the EEC relay, I remembered that the red ignition wire also goes to the fuel pump relay and it was at this point that it occured to me that if the relay for the EEC was corroded inside, why couldn't the fuel pump relay? So I put one in that I got from the wreckers and...IT WORKED!!!!

I am sooo happy now. All I have to do now is rewrap the wiring and put everything back together


thanks for offering to help Reaper, but I have it under control, but I will keep you in mind next time.
 
#30 ·
Good to hear Walt. :beer_cheers:

I just got home, and my buddy suggested that if the relay was corroded, the wiring and connectors could be too, so cut back about 6-8" of the wiring and put new ends on. Guess he was kinda close. :laugh



 
#32 ·
Yeah it sure is a relief to get it fixed.
I was just thinking about it and it occurred to me the reason this all happened, was because I ended up bursting the pressure line in my power steering pump and then cleaning the fluid from the engine bay, by spraying that citrus spray. It was this spray that got this to happen for the first time almost 2 weeks ago. The problems I have been having was inevitable, it was just sped up by the degreaser.
All in all, it worked out for the best because it happened at home and it got fixed with no serious pressures to get it done rather then in the middle of nowhere or while miles away from home with limited tools or a roof over my head.
 
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