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Discussion Starter · #1 ·
I was troubleshooting an electrical problem in my B300 RV when I created a new trouble! :frusty:

While checking running lights to see if they worked, I bumped the unfastened instrument cluster and its electrical circuits hit the edge of the metal dash housing. Bzzzapp! The running engine "stumbled" but kept going. I shut it off, examined everything for burned or otherwise damaged components (including fuses - none blown) and tried to start the engine. Nothing - except a small burn mark at the point of contact with the dash.

This is one reason why I don't work as an automotive electric technician. :facepalm:

Everything one would expect to work with the switch in the "run" and "acc" positions works. Good thing the short lasted less than a second.

I got out my multitester, removed the ignition, and tested it according to the instructions in the Haynes manual.

IGN 1, key ON: FAIL (However, with the key turned to "start," current passes through)
IGN 2, key OFF: Pass
ACC, key ACC: Pass
ST(ART), key START: Pass (!)

The Haynes text reads in part, "[Turn key to Run], connect the [ohmmeter probes] to the B (battery +) terminal and either of the I (ignition) terminals - there should be continuity." Either terminal? Does that mean that only one or the other needs to allow continuity? I'd think it'd be both. Any thoughts?

Personally, I hope the internal switch connection is what got "fried," because it's easier to replace the switch than find wherever the circuit got broken.
 

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The fact that you have power in every position but IGN does indicate a zapped switch. The other failure from a major short would be the fuseable link from the battery, but that would kill every thing.
 

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The reason you get power on IGN1 seems to be that it is backfeeding from the start when it is engaged. You did not give the year but I expect you have a blown switch.
 

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There are several fuseable links at the LF firewall. I would want to rule any of them out as being open first. The one that you pull gently on and stretches would be the bad one. Avoid poking through wire insulation with a test probe.
The switch may be easily taken apart for inspection, look for any burnt copper contacts. Although these switches do wear, they are usually pretty robust with a current surge.
The cluster ammeter wires handle high-current with fat wires and may be what shorted. Does the ammeter pointer still work?
 

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Discussion Starter · #5 ·
Dr. Dan's Caravan said:
IGN 1, key ON: FAIL (However, with the key turned to "start," current passes through)
IGN 2, key ON: Pass
ACC, key ACC: Pass
ST(ART), key START: Pass (!)
All with key OFF: Pass

The Haynes text reads in part, "[Turn key to Run], connect the [ohmmeter probes] to the B (battery +) terminal and either of the I (ignition) terminals - there should be continuity." Either terminal? Does that mean that only one or the other needs to allow continuity? I'd think it'd be both. Any thoughts?

Personally, I hope the internal switch connection is what got "fried," because it's easier to replace the switch than find wherever the circuit got broken.
The above quote from my own post is corrected information. I had typed "OFF" by mistake in the IGN 2 entry.

I bought a replacement switch thru. online order from O'Reilly Auto Parts (great service and fast, by the way). Before I went through the trouble of installing it only to discover the problem is something else, I used my multitester on it and compared with the existing switch. The results are identical. The only way to tell the two switches apart is the new one looks cleaner (no suprise).

ImperialCrown's suggestion about a blown fusible link seems the most plausible alternative explanation. The rub is that I only see one in the expected location near the firewall. And that one is between the positive battery and the whole bloomin' electrical system, so that ain't the bad one.

I'll send a photo when I get back to the RV, probably when the weather warms up. No fun working on a non-urgent problem in the subfreezing temperatures.
 

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IIRC, my 87 B250 had fusible links between the brake booster and firewall. Not sure what year your machine is.
 

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1976? A Dodge B-van electrical service manual/wiring diagram may help although many RV upfitters add their own wiring that can be more difficult to figure out.
 

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Discussion Starter · #9 ·
Dr. Dan's Caravan said:
I was troubleshooting an electrical problem in my B300 RV when I created a new trouble! :frusty:

While checking running lights to see if they worked, I bumped the unfastened instrument cluster and its electrical circuits hit the edge of the metal dash housing. Bzzzapp! The running engine "stumbled" but kept going. I shut it off, examined everything for burned or otherwise damaged components (including fuses - none blown) and tried to start the engine. Nothing - except a small burn mark at the point of contact with the dash.

This is one reason why I don't work as an automotive electric technician. :facepalm:
Truth-is-stranger-than-fiction update: On a rare warm day today I put the switch back in since it wasn't the problem. On a whim I hooked up everything after looking at the Haynes manual, lest the switch "failure" had been due to forgetting to put back a connector and therefore leaving an open circuit. Well...the starter cranked and the good ol' 360 fired right up.

I took the RV to a gas station, added some fuel (the gauge wasn't registering), went to leave...no start. To make a long story mercifully short (leaving out the part about trying to hire a tow truck), I tried, out of desperation, starting it with the shift lever in Neutral and success. (?!)

More funky stuff: the flashers flashed when the head lights were on (it was right around sunset) and the turn signals wouldn't work. I had to switch 'em off so I could signal my turns. Good thing it was still bright enough that I didn't need runing lights and I only had to drive a couple of blocks back to the storage lot.

Since the hazard/turnsignal problem is new, I'm wondering if maybe that accident with the panel hitting the metal damaged the circuit board and created some weird short-circuits.

I put electrical tape over the edge of the metal dash opening to avoid repeating the mishap during future troubleshooting. Could be like shutting the barn door after the horse got away. Oh what fun this is going to be to follow all those wires in the dash!
 

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Physically and electrically check every fuse you can find. The brief short may have simply blown a fuse and you may be getting current back feeding through another circuit causing the unusual electrical issues. Sometimes a fuse will "blow" with a break so small that it's almost undetectable by eye. If the fuses are all good then a bad fusable link is the most likely culprit. Most passenger cars have more than one and they do differ in their current capacity rating. Typically they're color coded by wire gauge and the insulation is usually softer and more pliable than the regular wiring.
 

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Hello DrDan68108 ,
Unfortunately, I have to say that I did a similar thing. I travelled with a friend east a few hours drive to pick up an RV he wa as planning to buy off a craigslist ad, the seller said it probably needed a coil and it would'nt start. He had bought it in Oregon a few months prior and after driving it for only about 45 minutes it backfired and died and he couldn't get it started again. Had it towed for $1000 to the closest town in California with a shop that would work on it and enter my friend and I. He just wanted to get rid of it to recoup some of the $3500 he bought it for. "It", being a 1979 Dodge B300 Model F30 Lazy Daze motorhome with a V8 360 and a 4bb Carter thermoquad I believe, if everything is still original. The mechanic didnt want to deal with it either because it was electrical and he doesn't specialize in electrical. So he advised us that we could jump the coil to the battery and it would start right up.
Ok, I'm no mechanic, but my father was , and he always encouraged me to NOT hook up any hokey electrical stuff or else you could fry everything. So I decided to attach shutting off switch to the wire jumping to the coil, when ~ZAP!~ Smoke came from under the steering ,column and I realized the steering column is bare painted steel and the metal contacts from the shut off switch had been touching it. However, after charging the battery and a few sprays of starting fluid the thing turned over and we started on our way back to the coast. It was nearing sunset. About 30 minutes into the drive home while coming down a slight mountain grade, the sidemarker lights appeared to get dimmer(I was following at the time), and the taillights also. I should mention that I never could get the brake lights to work , nor get the dome light to go OFF (so I removed the bulb) even after changing every fuse In the glove box fuse block. About this time as the lights were getting dimmer the engine began to backfire, small at first and then pretty forceful until the engine cut out and the lights were barely visible. We coasted to the nearest exit and parked. The battery was dead and no matter how long we let the jumper cables run on it, it wouldnt turn over at all. So, I started looking over everything and found that a few plug wires including the coil wire, were very old and brittle and barely making a connection, the battery cables were rather loose and the positive clamp was severely deformed but useable. I checked the plugs and they were pretty old, and the air filter was filthy. So we finally got it towed to the next exit with a gas station and drove to town to get parts. I have replaced the plugs,wires, rotor, distributor cap, battery, alternator, air filter, fuel filter, bench tested the starter and it's good . Also replaced the ignition control module, another module next to it, and have been trying to find the proper wiring harness for a tilt wheel ignition switch. I just got the switch I ordered off ebay and it looks identical to the one for no tilt. This presents a problem because it would just bypass the ignition switch thing that's mounted to the steering column. There are a LOT of different electronic ignition switches on this particular model. 1979 was a pivotal year for their electronic ignition apparently. Anyways, I could use some narrowing down what the problem could be if I'm still not getting enough spark to fire it up.it jus ttb wants to crank and crank so that's why I'm really trying to repair the ignition and see if it'll fire up. Does anyone else ha e a 79'? Has anyone else experienced a similar experience? It looks like someone just replaced the exhaust because the muffler and pipe look brand new. It looks like someone rewired the stop lamp switch and the battery feed but I cant find this "IGNITION SWITCH" that's mouth red to the steering column anywhere on any wiring diagram, not even in the Haines manual. I have been stuck at this exit for almost a month!!! Please help!! Does anyone know the switch I'm talking about? Two plugs from a half circle connector plug into it. I want to go home.
 

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Ohand I changed the ballast resistor but dont know what the tiny inverter looking thing is under the battery. Maybe for the solar? And I also changed the pcv valve and the inlet valve and some vacuum lines and throttle springs, and tightened the belts. I'm trying to think of anything else I put on it.... I'll add it in if I remember anything. Thank you ANYONE THAT CAN HELP!!ANY AND ALL ADVICE WILL BE GREATLY APPRECIATED. THANK YOU VERY MUCH!!
 

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Welcome to Allpar. I see the melted plastic at the ignition switch connectors, but the brass terminals appear to have been already replaced with the improved ones (the spring-loaded tongue) that makes a more secure connection.
These early trucks had problems with poor connections. The heat from a high resistance would melt plastic and burn wires, especially ones that carried significant current. I'm surprised that there weren't more underdash fires than there were.
The bulkhead disconnect at the firewall was another area for corrosion and heat from poor connections. Some I had to break apart because the plastic had melted together. Being close to the battery also increased the likelihood of acid misting and corrosion. I would take the connector apart for inspection.
The electrical on the B-van is different enough than the D and W (pickups) where it might be helpful to have the correct factory service manual. Don't bother with Chiltons or Haynes.
Redo the portion of the electrical system that needs service and you should have a reliable vehicle.
A local library may have wiring diagrams in Motor, Mitchell or Alldata-online references. I was lucky enough to find factory service manuals for our 1977 Ford E350 Honey RV at the downtown library. Photocopy what you need.
 

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The Ign switch on my 89 b250 can slide up and down on the column, and when far out of adjustment, not engage the starter.

I love having a factory service manual but I have found the wiring diagrams to sometimes not be accurate as to wire color or pin position of connectors, or wire gauge. even accountng for the fact that SAE gauge wire/cable can be 6 to 12% thinner than AWG.

My main fusible link between alternator and battery failed, but did not stretch out or look burnt. That failure description sent me on an stressful wild goose chase once.

Caig DeOxit d5 or D100 for really badly corroded contacts, cannot be beat, or even approached by other 'electrical contact cleaners.

However, it is too expensive to waste trying to blast old Dielectric grease and detritus from electrical connections, so CRC QED electrical contact cleaner is good to use first, just dont think it does anything about oxidized contacts, and don;t believe that just because a connector has a lot of Dielectric grease still in it, that all is well within especially one 40+ years old.

I've flushed what appeared to be clear scotch tape from a dielectric grease stuffed connector.

In the dental section of your local pharmacy, there are the mini bottle brushes designed to get between teeth. These 'Den-tek' brushes and some precision tamiya swabs soaked withwith first CRC QED cleaner, then Caig DEoxit, will make brass pins gleam like polished oiled gold and elininate the connector/ contacts as an immediate culprit and future culprit too.

The Caig Deoxit lineup, is dang near magical electrical juice. Though I despise their latest style of spray can which seems to waste 5 more product than it dispenses. its got the pivoting yellow permanently attached straw
 
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