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Quickly fix a combo of dead dome light, radio, and mirror motors

If you own a second generation Ram truck, you might find yourself in the cross hairs of a mysterious fuse called the “Ignition Off Draw” or IOD. On trucks like the 1998.5 to 2001 Ram 3500 5.9 liter Cummins Turbo Diesel, one tell tale sign you have an IOD fuse issue is that your electric mirrors, radio, and dome lights are all not working. This post covers exploring and troubleshooting issues related to an IOD fuse.

First, the IOD fuse is a 10amp fuse placed in position #12 on the fuse panel that is located on the far left side of dashboard on the interior of the truck. This panel is accessible when you open the driver’s side door. The first oddity you will notice is that this fuse is protected by a “black box” like cover. You will want to start by opening it. Here is how you do that:

Once your fuse is removed, inspect it and replace it with a new 10amp fuse. Close the latch on the black cover and push the fuse back into place. You can then turn on your ignition and inspect your electronics in the following order:

• Inspect the dome lights and verify they are working
• Turn on your radio and verify it has power
• Place the mirror adjustment knob to the passenger side mirror and confirm the motor works
• Place the mirror adjustment knob to the driver side mirror and confirm the motor works

If any of the steps above blow the IOD fuse, you will know where the troubleshooting needs to begin.

Pinched Mirror Power Cable

One classic source of an IOD fuse problem is in the electric mirrors. Many second generation RAM owners chose to upgrade their mirrors to more modern ones. When you do this, there is a trick to routing the electric motor cable through a designated channel in the mirror frame. If you fail to do this, when you tighten the mirror it will crimp the power wires into the metal frame of the mirror and cause a short. If after replacing the IOD fuse the mirror motor works for a couple of seconds and re-blows the fuse, you likely have this issue. You can view this YouTube video to see how to route your wires.

One of the desired traits of second generation Ram trucks is that they are simple to troubleshoot, fix, and maintain. One of the exceptions is the IOD fuse. It isn’t documented in the owner’s manual, its black box cover is tricky to open, and the correlation of mirror motors, dome lights, and radio lead the average person to think the problem is much worse than it appears.

Vintage Dodge Ram diesel powered pickup trucks are grouped into Generation 1 and Generation 2 trucks with references to 12 valve and 24 valve versions of their Cummins B series engine. However, the powertrain evolution doesn’t directly align to body styles. In order to answer the question poised in the title of this article, we will need to unpack both story lines.

Body Styles and Platforms

Dodge introduced its first generation Ram platform in 1981 and continued to evolve and produce it until 1993. The truck had a timeless style featuring square headlamps, bracket mounted mirrors, a boxy cab, and dog dish wheel caps. Though the majority of these trucks shipped with gasoline power plants, in 1989 an optional 5.9 liter Cummins inline six diesel engine was introduced. This would become known as the infamous 12 valve Cummins B-Series.

In 1994 Dodge introduced its second generation Ram which featured a complete structural and aesthetic redesign. The commercial results boasted significant increases in sales and broad consumer applause. The aesthetics of this truck would carry over and influence the style of the truck into the 21st century. Still, the path to get there was not a simple one.

In 1986 Chrysler engaged an internal design studio to come up with the generation 2 design. The project was code named “Louisville Slugger”. Unfortunately their output more resembled a mini-van than a truck. It also lacked the physical capacity to house larger engines including the Cummins diesel platform. The design was deemed a failure and scrapped.

Chrysler pivoted on the “Louisville Slugger” failure by handing the project to its newly acquired AMC design studio. AMC delivered project “Phoenix” with a design worthy of a truck but it lacked originality when compared to similar designs by Ford and GM. In 1988, this design was also scrapped. For its 3rd attempt, the design teams shifted to design concepts inspired by WWII vehicles as well as big rig designs currently in the market. The third time was the charm and the result was what we refer to as the “Gen 2 Dodge Ram”.

Now that Dodge got the styling right, it is important to note that the second generation trucks continued to feature the 12 valve B-Series Cummins through 1998. Midyear through the 1998 year model, at the mercy of stricter emissions and efficiency regulations, the final 12 valves rolled off the assembly line. Their successor was basically the same engine featuring a different cylinder head and a new injection pump system. Though doubling the valves for a total of 24 was efficient, the fuel pump evolution proved to be problematic and was not well received by diehard diesel consumers.

Both generation 1 and generation 2 Ram platforms featured a variety of bed lengths, SWD/DWD configurations, and two door/four dour cab options.

Now that we have a basic understanding of the Gen 1 and Gen 2 body style evolution, let’s talk more in depth about diesel power plants.

5.9L Cummins B-Series Power Plant

The Cummins B-Series engine was produced from 1984 to 2007 in both inline four and six cylinder configurations. Since 1989 Dodge Ram trucks have featured two major generations of the 5.9 liter, inline six configuration–the BT and the ISB.

5.9 Liter 6BT

From 1989 to mid 1998, Dodge Ram’s diesel platform was a 12 valve, mechanically injected, 5.9L turbo diesel engine. At their peak, these engines produced 215 horsepower and 440 foot pounds of torque. Known for reliability, ease to work on, and mechanical injection pumps, this engine will go down in history as a favorite amongst owners.

What is important to note is that mechanical fuel pump on the 12 valve platforms differed from the first generation and second generation body style trucks. First generation 12 valves had what is known as a VE pump. The VE is a good pump; yet, had limited tuning options. The second generation 12 valves featured the Bosch P7100 which is considered the best mechanical fuel pump for reliability and performance tuning. P7100’s offer full a variety of opportunities to modify and tune just about every component in it.

12 valve powered Dodge Rams are still on the road today. Due to ease of modification and stout components, 12 valve engines are also popular in racing and sled pulls where they are dialed up to 800 horsepower and greater.

ISB 5.9 Liter

In mid 1998, Dodge incorporated a 24 valve version of the Cummins 5.9L platform. The primary driver for the change was meeting stricter emissions standards. In addition to doubling the number of valves in the cylinder head, the main difference in this new platform was that the switch from a completely mechanical injection pump (P7100) to a computer controlled mechanical injection pump called the Bosch VP44. Now, in addition to mechanically altering the injection pump for performance tuning, owners have computer related tuning options as well.

For the most part, the rest of the engine remained the same

Problems and Shortcomings

Since the 80’s Dodge Ram pickup trucks have been known for reliability; yet, like any automobile have had their problem list. For the most part, the Ram’s problems are easily solvable. The shortlist includes hood paint, dashboard quality, a faulty dowel pin, clutch plate durability in manual transmissions, and overall quality in automatic transmissions. From a platform perspective, there is no clear consensus as to whether a generation 1 or generation 2 Ram truck is superior. Where the discussion gets interesting is evaluating those generation 2 trucks that shipped with a P-Pump equipped 12 valve Cummins BT or a 24 valve ISB Cummins power plant. It is at this point that most Cummins enthusiast would start in with a statement about the superiority of the mighty 12 valve platform. Still, from a real world usage perspective both have pros, cons, and a problem list.

Which Dodge Ram is the Best?

In order to answer this question, it is crucial to understand who’s asking the question. Let’s break this down into a few personas.

The Power Hungry

When tuning any diesel engine you have to balance the goal of generating power with the limits of handling the power. The diesel platforms in both Generation 1 and Generation 2 trucks are equipped with rugged components that can handle power. Thus, it really comes down to generating power and the key component in that mix is the fuel pump.

If you are looking for a 5.9L Dodge Cummins for racing, sled pulling, or simply tuning for maximum power, a P-Pump equipped Second Generation Dodge Ram with a 12 valve engine is the clear winner.

Construction and Agriculture

If you use your Dodge Ram as a part of your livelihood, your primary need is likely reliability. With that said, stock 12 valve and 24 valve platforms do lack a few horsepower required for pulling large equipment or heavy loads. The clear choice for power and reliability is the 24 valve, manual transmission, generation 2 Dodge Ram. Here’s why.

Energizing and bullet proofing a 24 valve Cummins Dodge Ram is as easy as 4 steps. First, replace the uplifter pump with a FASS or Bully Dog system to ensure your VP44 doesn’t fail due to fuel starvation. Second, add an Edge Box to allow you to quickly manipulate injector pump timing via a sturdy 3 way switch. Third, install a basic 4″ turbo back exhaust system to free up exhaust flow. Last, replace the paper air filter with a drop in K&N filter to free up air intake (a new air box is not required). With these simple steps, you will easily add up to 65 hp and 180 foot pounds of torque while ensuring reliability for day in, day out work. Any mechanic can perform this work and you aren’t dependent on a specialized diesel tuner who is experienced in the ins and outs of a P-Pump.

The Nostalgic

If you are a collector or simply a Dodge Ram aficionado, you have a real decision to make. Outside of true collector factors including originality and condition, rarity is a driver. The Generation 1 production numbers are exponentially lower than their Generation 2 counterparts. This makes a Generation 1 truck attractive. However, there is a smaller population of pre ’98 1/2 Generation 2 trucks that shipped with 12 valve engines. Those Generation 2 Dodge Rams have both the design that inspired the future as well as an engine that is favorite amongst diesel fans. The choice is yours.

Unless you are a collector that is specifically looking for a first generation Dodge Ram Cummins 5.9L turbo diesel, the second generation Rams offer both the coveted 12 valve P-Pump power plant as well as the 24 valve edition. The answer to the question seems clear.

Second Generation Dodge Ram trucks with 24 valve Cummins engines rolled off the assembly line with good overall performance. With manual transmission versions boasting numbers just shy of 240 horsepower and 460 foot pounds of torque, there is plenty to work with on these trucks. However, if you’ve ever hauled a really heavy load or pulled a large trailer, you’ll admit the need to downshift in order to keep moving. There are three no brainer upgrades that can change that. Best of all, they are simple and affordable.

High Flow Air Filter

Diesel engines need to breath. Options to improve airflow include cold air intakes and high performance air boxes. However, if you aren’t careful, you can actually go too far with an air intake upgrade and end up working against your end goal. Most experienced diesel tuners will admit that if you are looking for upgrades to aline with practical performance gains, a drop in high flow air filter is all you will need. K&N part number 33-2056 is one option to consider.

Edge Box

Diesel trucks require fuel. Cummins 24 valve platform employs a mechanical injector pump that is controlled by a computer module. By hooking into the truck’s computer system an owner can responsibly and safely manipulate both timing and fuel pressure. The easiest and safest way to do that is an Edge Box.

A properly installed Edge Box is about a 90 minute job and includes a 3 way toggle switch that is mounted in the cab. The result is power increases ranging from 20 to 65 horsepower and 45 to 180 pound feet of torque. You will want to read the instructions carefully and be mindful that the most powerful setting is not recommended for towing applications. Note there is a version for 1998.5 to 2000 models and a version for 2001 models.

Turbo Back Exhaust

Now that you have solved for air intake and fuel, your truck needs to let the exhaust turbo go to work. The most cost effective way to do that is by replacing the factor exhaust with a turbo back exhaust system.

There are a lot of options when it comes to 24 valve Cummins exhaust upgrades. You can go big, loud, and fancy. Still, it all comes with a price tag and doesn’t necessarily buy you more power. An aluminized 4″ turbo back exhaust is a cost effective option that pairs well with a drop in air filter upgrade and an Edge box. One option in this category is MBRP’s Performance Series 4″ Turbo Back Single Exhaust. These are heavy duty, designed to fit Gen 2 Dodge Rams, and add a nice note to the exhaust sound without taking it too far. Here is an actual recording of a cold start:

A Cummins 24 valve platform can be fitted with a wide variety of tuning options. With new injectors, fuel pumps, and custom tuning modules, you can take these platforms to 500 horsepower and beyond. Still, these upgrades come at a cost and can impact the life of your engine and transmission. If you rely on your Gen 2 Dodge Ram 24 valve Cummins for work and value its reliability, consider the modest upgrades mentioned in this post.

Though second generation Dodge Ram trucks were the result of a lengthy and controversial redesign process, they are representative of old school trucks and don’t come close to offering today’s comfort and safety features. Still, with a few cost effective upgrades, you can greatly improve upon your experience and safety.

Mirrors

With the release of the second generation Ram, away went the first generation’s bracket mounted mirrors and in came an integrated power, heated mirror system. Though this was a significant upgrade, the problem with them is they are small and are not very helpful when pulling wide trailers. They also lack moon mirrors which are very helpful in eliminating blindspots.

For a few hundred dollars you can upgrade your gen 2 mirrors to a more modern design that is not only compatible with electric adjustment and heating system but they don’t look out of place. They also feature builtin moon mirrors, a manual fold up trailer mode, and a manual fold in parking mode. One option is the Trail Ridge mirror set.

Windsheild Clear Tint

Most second generation Rams shipped with factory air conditioning. Dodge’s AC systems are reliable and good. Still, Ram Club Cab options create a lot of interior space and in hot climates the factory AC can reach its limit. The quickest way to lower summer temperatures and make the air conditioner more effective in any car is clear, heat reducing windshield tint. Go do some research and talk to your local window tinting shop.

Carhartt Precision Seat Covers

Let’s face it, the second generation Dodge interiors are really dated. One can chalk much of it up to charm but when it comes to the cloth seat option, they are hot, stick to your clothes, and hard to clean.

Carhartt makes a precision seat cover systems out of tightly woven fabric that stays cool, repels water, and are really easy to clean. When ordering these seat covers you are presented with options to accommodate head rest shapes, seat through seat belt designs, seat back, and center console options that varied greatly in second generation Rams. They also make a custom dashboard cover. Though a bit pricey, this is a comfort upgrade you will not regret.

Modern Radio and Mobile Setup

Single DIN radio upgrades have been commonplace since the 70’s. Back when gen 2 Rams rolled off the assembly line, radio replacements were actually an upgrade. The the evolution of mobile telephones and car entertainment integration, radio upgrades don’t make as much sense. Recent innovation in single DIN units actually afford older car owners a modern upgrade.

The Pioneer SPH-10BT is a $150 upgrade that not only brings hands free phone into your cab, it has a simple fold out phone holder that allows you to see Waze and Google Maps safely while driving.

Fans of the Dodge Ram Cummings platform frequently discuss generation 1 and generation 2 body styles. These discussions spill over to the classic 12 valve vs. 24 valve engines debate. There are actually several overlapping elements to this discussion and this article seeks to provide timeline clarity.

Body Styles

The Generation 1 body style was produced from 1983 to 1993. In 1989 Dodge incorporated a B Series Cummins diesel platform into Generation 1 trucks. In 1994 Dodge rolled out its long awaited Generation 2 body style and continued to offer the Cummins B Series platform.

Cylinder Heads

Dodge incorporated B Series Cummins engines with two different cylinder heads. Dodge Ram trucks from 1989 to 1998.5 featured a 12 valve cylinder head. In 1998.5 the platform switched to a 24 valve cylinder head.

Injection Pumps

Between 1989 and 2001, Dodge Rams equipped with B-Series Cummins engines featured 3 different mechanical fuel pumps. Diesel trucks manufactured between 1989 and 1993 featured Bosch VE injection pumps. Those manufactured between 1994 and 1998.5 rolled off the assembly line with the infamous Bosch P7100 injection pump. In 1998.5, in conjunction with the introduction of the 24 valve cylinder head, the VP44 pump was incorporated into the platform. The VP44 was the first computer over mechanical design which relied on a computer system control timing and other parameters of the mechanical pump.

Common Questions

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