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Unread 09-04-2008, 06:46 AM   #1
spshultz
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Odd circuit board in black case next to battery. What does it do?

This has been bugging me because I can't find any info on it in my Haynes manual but what in the world does that long PCB (printed circuit board) in the black plastic case next to the battery, relays and passenger side fender do? It's stuffed back in the corner under the test point connections and the relays on the passenger side next to the firewall. It was just dangling there and flopping around smacking the firewall. Is it for the intermittent wipers or maybe the A/C or ignition?

Thanks!
Shawn

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Unread 09-04-2008, 06:55 AM   #2
rustywrangler
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By all means, post a pic of that. I have never heard of such a creature in the pre FI YJ's.
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Unread 09-04-2008, 07:04 AM   #3
NEVER-ENOUGH
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Aftermarket alarm???? I'd like to see it too.
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Unread 09-04-2008, 08:06 AM   #4
Felonious_monk
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It is the diode/fuse assembly......I have no idea what it does either....but that is what it is.

I have an 88 4.2L it is shown on the wiring diagram on page 6-26 of my chilton manual.
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Unread 09-04-2008, 08:12 AM   #5
rustywrangler
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Quote:
Originally Posted by Felonious_monk View Post
It is the diode/fuse assembly......I have no idea what it does either....but that is what it is.

I have an 88 4.2L it is shown on the wiring diagram on page 6-26 of my chilton manual.
It also calls for one on my 89...... Not there. Do you have a picture of it???
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Unread 09-04-2008, 09:10 AM   #6
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Does it connect to the throttle linkage? Mines a 95 and thats were the cruise control is mounted.
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Unread 09-04-2008, 09:21 AM   #7
spshultz
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Unfortunately my wife has the camera so I can't take a pic now. I'll have to do that later tonight.
But yeah, there's definitely a diode on it.
The wires disappear into the loom and I really don't want to crack that loom open to trace them.

What is section 6-26 called in the Chilton's? Maybe I can cross reference that in my Haynes. Is it part of the charging circuit or cruise or lights or etc?
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Unread 09-04-2008, 05:38 PM   #8
Felonious_monk
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Quote:
Originally Posted by spshultz View Post
Unfortunately my wife has the camera so I can't take a pic now. I'll have to do that later tonight.
But yeah, there's definitely a diode on it.
The wires disappear into the loom and I really don't want to crack that loom open to trace them.

What is section 6-26 called in the Chilton's? Maybe I can cross reference that in my Haynes. Is it part of the charging circuit or cruise or lights or etc?
It black right? With a circuit board inside of it.....there are about 5-6 wires running into it with nothing coming back out

Its in the electrical diagrams section. Under 1988 4.2L engine wiring.

I only know what it is becuase I stubled upon it when rewiring the engine bay. I still dont know what it does. I did cut the wires that I didnt need that were running to it. I left one or two still connected though.....one was for the rear defroster, and I can't remember what the other is for.

Good Luck
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Unread 09-05-2008, 08:25 AM   #9
spshultz
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OK. I hope I can get these pics to display correctly.
Here's an outside shot of the little black case/box and then a somewhat blurry inside pic.
Like Felonious said, there are about 5 or 6 wires coming out of it.
I definitely see orange, black, pink? and purple? or violet? and one other color.




Last edited by spshultz; 09-05-2008 at 08:35 AM..
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Unread 09-05-2008, 08:53 AM   #10
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I did some digging around and found that box tied up back near the brake booster. When I undid the zip tie, it reaches all the way over to where your pic shows.

I did a quick test and that box is in fact what I said it wasn't earlier. It has the controller for the rear defroster etc.
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Unread 03-26-2009, 11:54 AM   #11
Mr-Rock
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Hi, I'm new to the Forum so I hope this is where I should ask this question.

What are the two relays for next to this black thing?
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Unread 03-26-2009, 12:08 PM   #12
Burnerman
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One is for the electric choke. I can't remember what the other is for. I was gonna ask the question about the black diode box, now I know. I just left that stuff alone. The 2 plugs on the top are diagnostic's on the pulse air system.
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Unread 03-26-2009, 12:18 PM   #13
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Quote:
Originally Posted by rustywrangler View Post
I did some digging around and found that box tied up back near the brake booster. When I undid the zip tie, it reaches all the way over to where your pic shows.

I did a quick test and that box is in fact what I said it wasn't earlier. It has the controller for the rear defroster etc.
I think there is some crap in there for the sol-vac idle kicker chumpy too.
I accidentally chopped mine out with the emissions wiring.

Quote:
Originally Posted by Mr-Rock View Post
Hi, I'm new to the Forum so I hope this is where I should ask this question.

What are the two relays for next to this black thing?
The one towards the rear is for the electric choke, & the forward one is for the intake manifold heater.

I went to a cable for the choke when I did the MC2100 swap.

My heep's P/O had connected the blue choke wire from the choke , to the intake heater (red wire). It's supposed to have the Pink wire connected to the red wire.

The intake heater is good to have, & should be left alone.
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Unread 03-26-2009, 12:19 PM   #14
timatoe
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Choke and manifold heater.

Edit: I see Buckshot beat me to it.
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Unread 03-26-2009, 12:33 PM   #15
Mr-Rock
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Thanks, I'm putting in a dual battery tray and need to relocate these. I guess I can mount them under the new tray as i should not need to get to them often.
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