Reversed Battery Polarity on 1994 Chevy 34RQ, No Ignition or Lights

[trevorwillard]

I was replacing the battery yesterday, for the front engine etc...
I misread the terminals, got hot and ground backwards. Now I have no ignition. Cables now in correct position. Checked fuses under dash? What did I pop?

 

[LarsMac]

You Probably cooked your ignition system. Solid state systems do not like reversed polarity.
It's probably not cheap, but it is fixable.

 

[Kirk]

On a 1994 motorhome, check the specific engine type to confirm whether the original setup was electronic ignition or a distributor-based system. The 1994 P30 chassis was equipped with electronic ignition for the 5.7L and 7.4L gasoline engines. Some 1994 motorhomes were built on a 1993 P30 chassis and it didn't have the electronic ignition but used a distributor system.

 

[trevorwillard]

I have the distributor...
Had power at dash fuses, and solenoids under hood.
I couldn't get to the starter?

 

[trevorwillard]

I have the distributor...
Had power at dash fuses, and solenoids under hood.
I couldn't get to the starter?

 

[Mark_K5LXP]

It's fuel injected so has OBD. Probably OBD1 but my first pass would be to enable code flash mode and see what it does. If the ECM is fried it won't do anything. If it's alive it'll flash codes, and from there further diagnosis to prove where the start sequence is failing.

Mark B.
Albuquerque, NM

 

[DonTom]

It's fuel injected so has OBD. Probably OBD1

It had to be OBD1 because OBD2 did not yet exist in 1994.

No tester is needed, just a piece of wire to check codes on OBD1, for GM a wire between 1 & 2 on the OBD1 port and count the blinks, ignition on, engine NOT running.

It will blink 1-2 three times and any trouble code is after that will also blink three times until it gets back to 1-2.

Here is a list of OBD1 codes.

Handy to know, but it ain't going to help the OP after a battery is replaced reversed.

-Don- Bean Flat, NV

 

[CharlesinGA]

Reversing battery connections almost for certain blew the alternator diodes also. Never seen one that didn't blow when reversed.

 

[DonTom]

I couldn't get to the starter?

Does it NOT crank? Do the headlights come on? Give as much info as possible.

Starters are on the very bottom of the engine, usually cannot get to from the top.

-Don- Bean Flat, NV

 

[trevorwillard]

Not cranking, also no headlights as well

 

[DonTom]

Not cranking, also no headlights as well

That COULD be good news! For now, what I would do is ignore the engine stuff and try to figure out why your headlights are not coming on. In a 1994 vehicle the head lights should NOT be sensitive to a reverse battery. Perhaps something made you lose ALL power before anything could be damaged.

Troubleshoot only the very simple stuff for now, do not YET get into engine electronics until the simple stuff works.

-Don- Bean Flat, NV

 

[Jubilee]

Hopefully fusible link or high amp fuse blew before damage to ecm or alternator. Being GM, probably fusible link.

 

[John From Detroit]

Ok one feature of many cars is what is called a "Fusebable link" this is a length of wire.... That doubles as a fuse.. May be hard to spot but it may connect to "Battery" terminal on the starter solenoid.

You need a test light (A volt meter can be used but a test light is easier)
Start at battery Clip to unpainted metal and tip to battery Bright light = Good

No move to the other end of any wire on the positive terminal if more than one wire on positive test both.. The move on to the farend or each additonal wire

Problem is between bright and dark

 

[Kirk]

You need a test light (A volt meter can be used but a test light is easier)

If don't have one, they are available at any auto parts store, Walmart, Target, Amazon, and most anywhere that has an automotive department. To trace power from the battery, just put the alligator clip on the negative post and then use the icepick like probe to check along the route. The light means voltage is present, on light means it is not. But that does not tell you how much voltage you have. It is possible that your battery was destroyed and has no significant voltage. Not probable but possible.

 

[Mark_K5LXP]

Agree that no lights is a major clue. With that vintage of chassis the light circuit amounts to a continuity path between battery and lamps.

As far as polarity reversal goes, that's among the conditions many (but probably not all) systems/modules are tested per various SAE specs. I would expect the likes of an ECM to survive that. But it's quite plausible some other devices didn't, or they tripped a protection device like a fuse or fusible link. Time to break out the test light and seeing where it leads.

Mark B.
Albuquerque, NM

 

[trevorwillard]

the saga continues...
Today I was able to work on it for about an hour, still no lights. It looks as though I have no dash lights either. My OBD1 Port is not responding...
My previous photo was for the electronic ignition, with the distributor.
The way the RV is sitting, there is a slight Hill, on the passenger side.
I do not have access to the starter area. Currently
I do have power to the solenoids, which are located under the dash.
I wish I paid more attention, to my father, reading electrical diagrams...
Thank you all for the help.
Hopefully I'll get to the bottom of this problem...

 

[trevorwillard]

I was using a test light

 

[DonTom]

My OBD1 Port is not responding...

I would not expect it to. That is why I said start with a simple circuit, such as the headlights or anything else that is simple which should have 12V but doesn't.

Seems nothing is getting the 12 volts from the engine battery. Find the simplest circuit you can find to troubleshoot.

-Don- Sacramento Pass, NV

 

[John From Detroit]

I"m guessing a fusible link fused. And the test light Kirk posted an image of is a very useful tool for finding it. (Thanks Kirk)

Short OBD-1 Story.. car started running bad, pulled off. Shorted the pins, read the code called the mechanic, he told me not the spe3cific but the error class (Emmissions control) Popped the hook re-connected the sensor that had become unhooked (on the hose side not wire side) and varoom.

Now it's OBD-II so a OBFD-Blue Tooth and Torque on the phone

 

[Kirk]

I do have power to the solenoids, which are located under the dash.

Are you using a test light, or a voltmeter? Have you measured across between the battery posts to verify what voltage it has? Is there a coach battery that might be supplying the solenoids under the dash? Have you checked for any voltage at the ignition switch?

You need to find out if there is a fusible link in the battery cable that has opened or not. That can be done either by checking with a test light as suggested, measuring with a voltmeter in the same way, or you could lift one end of the cable to make an open circuit and measure it with an ohm meter.