Battery Jumped Backwards - The Damage Done?

[DKirk]

Neighbor of mine has a few Reattas and his 1990 had a dead battery (turned out to be bad radio, another story) and went to jump the car with one of those "jump boxes".  He managed to get the battery leads switched, reversing the polarity for a few seconds. With the negative on the positive battery terminal and the positive on the negative battery terminal for a few seconds some damage has occurred. The ECM survived without issue, the car starts and runs fine. The 1990 digital dash reports "00 Error" and nothing else works (totally dark) except the "Test" button which correctly shows all of the display elements. The temperature control module shows "---" and nothing else. We have replaced the Instrument Cluster with a known good/working 1990 cluster, no change. We replaced the temperature control unit and nothing changes. We finally bought a remanufactured BCM, swapped the chips, and still nothing has changed, the Instrument Cluster continues to display "00 Error".  In reading forum messages there has been some discussion of corroded BCM pins, and we did find corrosion, but have it cleaned up now.  I don't have access to a wiring diagram just yet so I'm flying blind with the help found in these forum messages, but have not yet found a forum thread regarding reversed polarity battery jump and the damage done. Walked through all of the fuses twice now and the only burned one was the lighter/power connector.

 

Would anyone have any ideas on what to check for next? Is there a power relay somewhere that has been scorched, or possibly a fusible link somewhere that protected the circuit(s) from the reversal?

 

Any and all suggestions welcome! I've been really struggling with this, made more frustrating since the car starts and runs fine, just no dash, I'm thinking it is something simple. 

[fun car guy]

Speaking as one who's been there and done that, I wonder if you ever considered a blown fuse to be the problem?

[DKirk]

Fuse check was the first we did and found nothing but the cigarette lighter blown, assume we've checked them all, does anyone have a suggestion what to look for? Any ideas which fuse we should look at specifically.

[rogold]

You might want to check all fuseable links by the power junction box near the battery. Here is a link:

Reatta Owners Journal

[Padgett]

CPS ?

[2seater]

Intertwined with the Saving the car from the Crusher thread and included in FunCarGuys lost my interior and dash thread, was an item my son found on the black car from Daves89. We found that this car had either an alternator snafu or reverse battery hookup in a past life before it was in Dave’s possession. My do lost lights and dash on the 89 and to cut to the chase, he found a fuse that tested good but had extreme resistance from being hot enough to partially melt the plastic but not blow. It was a blue fuse but I don’t have much more info. at my fingertips. If in doubt on a fuse, replace it. 

[2seater]

This was the fuse 

 

 

[Brock]

2 hours ago, Padgett said:

CPS ?

Man, Padgett... I agree the car should have been better cared for, but involving Child Protective Services is a bit extreme, isnt it!? /s

[DAVES89]

55 minutes ago, 2seater said:

Intertwined with the Saving the car from the Crusher thread and included in FunCarGuys lost my interior and dash thread, was an item my son found on the black car from Daves89. We found that this car had either an alternator snafu or reverse battery hookup in a past life before it was in Dave’s possession. My do lost lights and dash on the 89 and to cut to the chase, he found a fuse that tested good but had extreme resistance from being hot enough to partially melt the plastic but not blow. It was a blue fuse but I don’t have much more info. at my fingertips. If in doubt on a fuse, replace it. 

Never noticed that fuse was bad. The PO tried swapping out the alternator without disconnecting the battery. Sparks flew and for the most part I had no electrical issues in the 8 years I owned the car...

[Philbo]

I have the 1990 manual. I can try to dig through the wiring diagrams and see if I find anything helpful later.

[Philbo]

Here are the wire diagrams for the fusable links.  It's a start. I can look up more stuff for you if you need.  There are many many pages on electrical troubleshooting lol 

[Philbo]

Here are some diagrams for the Central Power Supply 

[Philbo]

And finally a bunch of stuff on the IPC itself.  There is another section on IPC Dimming not included.  I can look up any other diagrams as needed. Just let me know.

[fun car guy]

In my case, I was replacing the battery and since the positive (red) terminal to the battery was missing and someone had cobbled up a substitute so I had two blacks instead, forgot which was positive and which was negative and naturally, guessed wrong and caused a short.  I quickly realized my mistake and switched them having noticed a few wisps of smoke from the old alternator.  Then I discovered I had no dash display at all and feared I had done serious damage.  I got a replacement cable for the positive and replaced the assembly hoping it would fix it and of course, it didn't.  Then I began my search for all the fuses, fusible links and relays checking them as I went, discovered there was another fuse block underneath the one on the cabin floor, passenger side  and found a blown fuse expressly for the dash displays that was clearly blown.  Imagine my relief when as soon as I put in a new fuse, I began to hear a steady series of clicks and presto, everything worked again.  It was the inner block, the lowest row.

I still had to replace the alternator but I really hope the solution to your problem is so simple.

[DKirk]

WOW, I wish I could convey the amount of thanks I have for all of the help given. I was not aware the CPS even existed, and will look for a solution tomorrow and HOPEFULLY report a successful repair!  Those diagrams are awesome, thank you.

[DKirk]

17 hours ago, fun car guy said:

here was another fuse block underneath the one on the cabin floor, passenger side

Can anyone describe this secondary fuse block "underneath" the one on the passenger? I've looked high and low down there, on the passenger side,  and can only see that front block of 5 fuses, nothing "underneath".  Using the wiring diagrams I was able to verify the CPS (Central Power Supply) was giving the dash and BCM 12v but could not find the 7 volt "Wake-Up" voltage. I have never or heard of this wake-up voltage, what does it do? With 12v at the dash and BCM I'm fairly confident the fusible links are good. 

 

 

[Ronnie]

There are hidden fuses behind carpeted panel on the side of the console. 

 

[2seater]

I don’t have my car home to verify, but I think the 90/91’s do not have that same fuse block. There is a fuse block on both sides of console and the sides are not removable like the earlier models.

[Ronnie]

You are probably correct 2seater. I always think in terms of my '88. I looked at DKirk's avatar on the side of the page to see what model he has and is says none so I took a guess. 

[DKirk]

On this 90 I'm dealing with both sides have access doors over the fuse boxes, nothing as extensive as shown above, and the 90 fuse box looks different than shown, five or so fuses are showing, nothing else above except what I believe to be is the CPS box.  The IPC Instrument Panel "Test" button correctly lights all of the IPC segments, so I'm left to believe the 00-Error that is showing is related to a lack of data to display. The ECM seemingly works as the car starts and idles fine. The BCM was replaced with a remanufactured unit, both BCMs making no difference to the display. The owner has 4 or 5 Reattas but this is the only 1990 so my ability to swap parts around and look around are limited.  

Edited January 23, 2022 by DKirk