ERV Fleet Defects

By Christian P. Koop

History, as many of us have learned, has a way of repeating itself-even when it comes to emergency response vehicle (ERV) maintenance and repair. What prompted me to go ahead and put pen to paper, as the saying goes, was a phone call I received from one of our vendors a few months back. The caller explained a problem he was encountering with a new rescue truck his dealership had recently sold but which was brought back with a complaint that during hard braking it pulled to one side. The dealer was having difficulty getting the problem diagnosed correctly. I quickly remembered and explained to him what the problem might be based on a similar symptom our shop had encountered 20 years earlier. It turns out it was the same problem. And, sharing this information proved valuable in getting the problem resolved sooner with fewer headaches for all involved.

Common Problems

For quite some time now I have felt the need to compile the major fleet problems or defects I have seen and experienced with ERVs over the years. By major, I am referring to those problems that affect a specific group of vehicles or are common fleetwide. Some of these issues might have been created by technical specifications that did not take into account real-world drive cycles, terrain, climate, vehicle weight, and other factors that can negatively impact ERV maintenance, reliability, and durability. Others were caused by poor design or just manufacturing defects that were not discovered until the ERVs were placed in service.

Many of these fleetwide issues manifest themselves right after the vehicles are purchased and placed into service. Other problems may take many months and even thousands of miles to rear their troublesome heads. My main goal behind writing about these past issues is that I feel some of the resolutions to defects and problems I have encountered over the years could be of value to others running into similar or even the exact same issues. This could be beneficial by providing information that may ultimately help cut down the time it takes to resolve similar problems. I am sure everyone reading this realizes that time is money, especially with today’s budgets, and getting the unit back in service as soon as possible is paramount to all those who are involved or affected by the problem-not to mention the taxpayers.

This article is not intended to bash manufacturers in any way for past problems. I will provide a brief history and background for each of the ERV fleet issues that I describe below to give the reader the best perspective in understanding what caused a problem and what those involved did to resolve it.

Alternator Failures

In the early 1980s, our department was using big-block gasoline-powered rescue trucks (aka ambulances) that were experiencing frequent alternator failures. Back then we were using a brush-type 165-amp alternator with internal rectification. In other words, it was an alternator with the diodes or bridge rectifiers built inside the unit as is still common today in most automotive, truck, and heavy equipment alternators. The root cause of the problem was extreme high under-hood temperatures causing the alternator diodes to die an early death. It was not because of an excessive electrical load. At the time, a gentleman out of Tampa, Florida-Whitley, if I recall correctly-began producing an external bridge rectifier to address the problem. Removing the stock bridge rectifiers from the excessive heat found inside the alternator and relocating them behind the grill area to receive cooler airflow resolved the problem.

Afterward, the shop modified the rest of the fleet, and alternator life was restored to acceptable levels. One very important point is that excessive heat is an enemy of charging systems, batteries, and electronic components. We went through this same ordeal just a few years ago when the wrong alternators were installed on a group of new trucks and we had to fabricate J180 mount (hinge- type mount) alternator brackets to install the correct alternators for external rectification to correct the problem.

Battery Life

While on the subject of charging systems and batteries, if you have a group of trucks that suffers from short battery life and the electrical and charging system is sufficient, make sure you have enough batteries. Automotive batteries don’t like heavy cycling, and if all things are equal, adding a battery to the pack may be all you need to correct the problem. Another helpful component is the solar panel. We have had some trucks being parked in new locations where shore power was not available, and parasitic drains were causing battery problems. We overcame this problem by installing solar panels to aid in keeping the batteries fully charged. We now specify solar panels for all our new units. They might be a little pricey to install, but they will pay dividends in the long term by increasing battery life in units that have marginal charging systems or those with parasitic drains that are excessive and are not on a shore power charger when they should be.


During an acceptance inspection of a pumper truck at the factory, I encountered a strange occurrence. As I was backing the truck into the inspection bay, the steering locked up for an instant as the truck transitioned from the driveway onto the bay floor, which was approximately an inch or so higher than the driveway leading into the bay. We reported the incident to engineering, but no cause was found at that time.

After the units were placed in service, we began getting complaints from drivers about an intermittent steering shimmy at highway speeds. The issue was confirmed, and the manufacturer was notified. These particular trucks have a mounting bracket, or subframe, for the steering gear box. In other words, the gear box does not bolt directly to the chassis frame rail but to a subframe, which, in turn, is bolted to the chassis. Because of a poor subframe design, it flexed excessively on certain highway surfaces, which caused the shimmy in the steering. Thinking back at the time, I realized this was most likely what caused the steering to lock up when I was backing up the new pumper at the factory. These subframes were recalled by the factory and were replaced-not once but twice-because the first modified replacement did not correct the problem completely.

This was not the first time we experienced steering box subframe issues. Ten years prior, the problem was complete structural failure of the subframes. The subframes were redesigned by the factory and all were replaced. Needless to say, because of safety, this is a very important component that the technicians need to check during preventive maintenance inspections. They must be alert to check for any cracks or signs of movement between the box and the chassis. They should also check bolt torque.

While I am on the subject of steering I must also mention that sometimes, although rare, a problem that manifests itself as a complaint of brake pull during braking may be a design defect in steering geometry. Back in the early 1990s, we had a large group of medium duty rescues that during heavy braking at highway speed-and only at highway speed-would veer left. The cause was a steering gear box mounted in the wrong location on the frame rail. During heavy braking, weight transfer and compression of the front suspension would cause the truck to steer left. The factory redesigned the draglink assembly and relocated the steering gear box to a position that would remain neutral during all conditions of front suspension compression while braking to correct the problem. This was very similar to the issue I mentioned at the beginning of this article.

Affecting Any ERV

These types of problems are not only difficult to diagnose and correct, but they can affect all makes and models, particularly custom built trucks. Not only can these types of problems be very troublesome to pinpoint and find the fix, they can also take considerable time to resolve. The other big factor here is that they can be quite costly to fix if the problem is not covered under the manufacturer’s warranty. Hopefully the information in the cases I cited above will be helpful in some way. I will continue to write about more of these cases in future articles.

CHRISTIAN P. KOOP is the fleet manager for the Miami-Dade (FL) Fire Department. He has been involved in the repair and maintenance of autos, heavy equipment, and emergency response vehicles for the past 35 years. He has an associate degree from Central Texas College and a bachelor’s degree in public administration from Barry University and has taken course work in basic and digital electronics. He is an ASE-certified master auto/heavy truck technician and master EVT apparatus and ambulance technician. He is a member of the board of directors of EVTCC and FAEVT and a technical committee member for NFPA 1071, Standard for Emergency Vehicle Technician Professional Qualifications.

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