I need some help with an electrical issue. i removed my dash to do some repairs, when i put it back together and plugged all the wires back in i think i got the fuel and temp wires mixed up .
Anyway i went to put the negative terminal back on the battery and as soon as it touched smoke started coming out of the panel where all the wires run through the firewall. i removed it straight away but now i have no power, no ignition or anything. i have inspected all the wires through the firewall and visually look ok (i think!), and no fuses have blown under the dash. can someone please point me in the right direction!?
i did notice one of the fuse type connectors on the voltage regulator looks blown (pic attached) could this be the issue?

thanks

 

Check for power at the fire wall... If it's good there.....
Check at the Amp meter....

 

those VRs aren't expensive; i'd replace that and see what it does.

 

First, the photo pictured is not the instrument panel IVR, it's the voltage regulator under the hood, and it won't cause a massive short of that order


Go over to MyMopar's tech section and download the proper service manual:

http://www.mymopar.com/index.php?pid=31

Here

http://www.mymopar.com/downloads/ser...ice_Manual.zip

Now these manuals are not scanned and set up with the proper "dash" page numbering, so you have to play with page numbers. The electrical section "8" starts on page 227

Wiring diagram index, page 332, engine compartment page 351

Instrument panel page 352, 353

A good write up on the problems with the ammeter, bulkhead connector, etc is here: PLEASE read this!!!! Even if you do not perform this modification, this article gives a GREAT overview of "how these work" and the problems that develop

http://www.madelectrical.com/electri...p-gauges.shtml

One key thing in this article is the simplified diagram I re-posted below:

This diagram shows some of "how bad" these are "not" fuse protected!!!! Follow along:

Start at the battery follow the wire to the starter relay and the FUSIBLE LINK from the starter relay through the bulkhead connector. THIS IS likely what you blew from the sounds of things.

Power continues to the ammeter, through the ammeter, and out on the BLACK ammeter wire. Notice the WELDED SPLICE. this is just what it says----a factory welded splice in the black ammeter wire. It is a few inches from the ammeter, taped up in the under--dash harness. This branches off and feeds:

The ignition switch

The fuse panel "hot" buss

The headlight switch

Depending on year / model, one or two other things, sometimes wipers

Depending vehicle options, there may be an accessory CIRCUIT BREAKER hung off one ammeter terminal to feed stuff like convertible top

NOTICE that the ONLY thing protecting ANY of this stuff is the fusible link!!!! I can tell you that is almost no protection at all!!!

If you were to short something ..........like the ammeter terminals themselves, this could happen.



To find this short, temporarily bypass the fuse link with some wire, and hook everything EXCEPT the battery ground up as per normal.

Take your test lamp and ground it, say, to the engine block. Hook the other end to the battery NEG terminal so that the lamp is in "series" with the battery to ground. A load, a draw, a short will light the lamp.

Make sure EVERY THING is turned off, and double check stuff like dome lights, trunk light, etc. If lamp is still lit, pull fuses one at a time.

If no change, unhook the main alternator output wire (stud / nut) and tape it off. If there is STILL no change, suspect the ammeter. Unhook the two wires, and clip them back together. If you STILL get a light, you need "some guy like me" to help you


Since you are "into" this once you find the problem, PLEASE go through the instruments to give them a chance............

1..Treat the instruments as an "end to end" system. You need everything in good shape

2..I'm not familiar with the PHYSICAL layout of your cluster, so some of this will be generic. First, make sure that the connectors (if any) which feed the cluster are good. Looking at the diagram, this cluster as well as a photo of the cluster on page 303 this may not apply. .........A bodies, example, use PC board and connectors

3...The old IVR is suspect. Replace it with a modern solid state one. RTE has a good rep Make sure the connections to the IVR are clean and tight

4...Make certain the gauge connections are tight

5...The senders are interchangeable for resistance. What this means is, a temp gauge can read fuel, and vice versa. The gauge movements are the same. So you can CHECK them for accuracy. The sender resistances for cold / empty is 73--75 ohms. At middle of scale (1/2) resistance is 23--25 ohms. Full / hot is about 10 ohms

Also if you Google around, there are various "test" procedures guys have discovered. For example, a 3V battery will give you full scale on the gauge unit. In other words, two D cells from a flashlight

For example you can go to Radio Shack and buy four 100 ohm, 1/2 watt resistors. Wire all four in parallel and this creates one 25 ohm resistor. Unhook your temp or fuel sender wire, hook this resistor to ground from the sender wire and turn the key to "run" for about 1 minute. The gauge, if good and accurate, should read 1/2 scale.


The posted photo shows a 3V power supply connected to a pair of gauges, and that they both read exactly the same, nearly full scale

 

thanks 440roadrunner for the very detailed response! this gives me some things to check tonight.
firstly I will follow the fusible link wire and check that and I will also replace the instrument panel IVR as I have a spare one of these already.

if it is the fusible link wire where is this likely to blow/what do I need to replace? sorry I am not great with electrical systems!

thanks

 

I believe NAPA has those, but I have not tried to buy one in a long time. You used to be able to buy them with the terminal into the bulkhead already on, and a terminal on the other end.

The thing is, those links have always been a very poor, last ditch protection. They sometimes blow AFTER the harness has melted into a smoldering mass of plastic and copper

 

Thanks again, it was the fusible link that had blown at the bulk head connector, until I get some fuse wire I have temporarily bypassed with a normal piece of wire and now everything fires up again. I now have another issue that you may be able to help with!
While I was doing the above job I also replaced the alternator with a Powermaster 75amp one which bolted straight in. Since both these jobs have been done (bypassed fuse & new alternator) I am now getting the ammeter showing a discharge when idling in neutral and worse when in gear e.g. stopped at lights. Sometimes the gauge goes right down and the car actually struggles to idle, even cut out on me once. The car has been sitting for quite a while, however it has never missed a beat up until now. I have not replaced any wiring when replacing the alternator, which reading other posts on here may have been a bad idea so I might swap it back out for now. It is duel field and I have tried grounding to the engine block with no luck. I am also going to replace the voltage regulator, I have one on the way now.
What could be the issue here?

Thanks

 

Not related to the immediate problem, but replacing the alternator with a huge larger one is a bad idea without performing the MAD upgrade or upgrading the ammeter wiring at the least. Even Ma knew the wiring was lacking, as optional 60-65 amp units could be had with what is known as "fleet / taxi" wiring, which amounts to heavier ammeter wiring run through separate grommets in the bulkhead, bypassing the bulkhead connector

Also MORE amperage does NOT mean better low speed charging, although "in general" the later "squareback" designs were better at low RPM output than the older "roundback" designs. The thing is, I know nothing about the quality, the performance, or anything else about Powermaster.

what are you using for a regulator?

It is an absolute necessity to ground the regulator and to make sure it absolutely has "same as" battery voltage. This is known as "voltage drop" and can happen both in the ground end and the ignition end.

I'm not too sure what to tell you about the low RPM problem. Again.........what are you using for voltage regulator?

Have you actually measured battery voltage when charging, at idle, at fast idle, and at "cruise" RPM?

Low voltage could STILL be related to problems in the harness, especially the bulkhead connector and ammeter circuit. That MAD article is IMPORTANT. It points out the major pitfalls of these old girls.

 

I'll do a few more checks and report back.

As for the voltage regulator, i have attached some pictures. What would be the best replacement for this?

 

The best known quality if you still have a one wire field setup (69 or earlier) is a NAPA / Echlin VR-2001 or a Standard (Blue Streak) VR-128 These are not cheap but probably the best.

IF you bought a later 'square back' which has an isolated field (incorrectly called dual field) you could add one more wire and buy a 70 / later VR. I don't know who makes the best quality

"New Old Stock" meaning factory original, NAPA, or good solid name brands. Unfortunately most of this stuff has suffered from the Chineseos