Chassis Components, Koop

Emergency Response Vehicle Modifications

Issue 6 and Volume 23.

Christian P. Koop

Christian P. Koop

There is no question that necessity is the mother of invention. Modifying emergency response vehicles (ERVs) is closely related to this ancient factual statement.

In my 35 years of being involved with maintaining and repairing fire and rescue apparatus, modifications to the equipment were required many times to keep the units safe and operational. Now there are several categories that these modifications can fall into. The simplest is just mounting new tools and equipment or simply mounting loose equipment for the sake of safety. Today there are a number of companies that provide specialty mounts for just about anything carried on ERVs. Second is installing electronic gear such as radios, laptop computers, thermal imaging cameras, and a host of other electronic equipment being installed as upgrades or new equipment to keep up with new technologies. The third category involves correcting a system or part that is either failing prematurely or one that never worked properly since the vehicle was purchased or placed into service. Some of these issues can be incipient and don’t rear their ugly heads until the warranty has expired or even years later.

Some of these issues can be corrected through the warranty, but with others, unfortunately, either the dealer or manufacturer flat out refuses to repair or is not able to. There are a number of reasons manufacturers will not become involved. Sometimes it may be because the equipment’s specifications were technical vs. performance type. Other times, it may be because preventive maintenance was not done according to schedule or there was abuse involved so either the dealer or manufacturer won’t agree to cover repairs. Whatever the case may have been, the following are examples of some of the numerous modifications performed over the years at the shop I managed for Miami-Dade County, Florida. The main reason I am writing about these modifications is to provide insight into the reasons they were done with the hope that they can help others in similar circumstances. As I have mentioned in past articles, history seems to repeat itself—even when it comes to ERV service and repair—and usually not in a good way. With each case, I will give background information to give the reader the greatest insight possible.

Short Alternator Life

In the early 1980s, the Miami-Dade (FL) Fire Department had a fleet of Ford E-350 type III rescue trucks with 460 gasoline engines. The main problem that kept reoccurring was very short alternator life. They were equipped with 160-amp alternators, and the internal bridge rectifiers (converts AC to DC voltage) were failing because of extreme heat. It was so bad that the solder holding the diodes in the rectifier would melt. Some of the hard run units had alternators failing almost daily. The fix was to remove the internal bridge rectifiers and install an external unit. The external diode pack was mounted behind the grille where the adequate air flow kept the diodes cool. The entire fleet was retrofitted, and this major headache went away. Subsequent new replacement fleet units were specified from the factory with a 200-amp alternator and with the external diode pack. Today some alternator manufacturers offer their own versions of the externally mounted diode pack.

Brake Life Issues

Between 1982 and 1983, the fire department purchased $27,000,000 worth of fire apparatus, aerials, and specialty units. Included were seven rear-mount 100-foot platforms and straight ladders. These were extremely heavy units weighing more than 80,000 pounds and were equipped with air brake front discs and drums on the two rear axles. The first major problems we encountered with the aerials were very short brake life and poor stopping distance coupled with brake fade. During the process of working with the manufacturer to resolve the issues, many tests were conducted. The problem was so severe sometimes that the brake drums would crack and pieces would fall to the pavement. I remember performing panic stops at highway speed and totally losing the brakes to fade after only seven applications.

The first thing we did, per the factory, was remove the automatic slack adjusters (ASAs) and install the manual type. The drums were expanding so much that when the parking brake was set at the station after a run, cracks would form during cool down. This did not work out, and we ended up going back to ASAs and having the crews not apply the parking brake at the station, using chock blocks instead. We also experimented with different friction materials and found that when we mixed a full metallic lining with an organic on a single shoe, it gave us the shortest stopping distance and longer life. This, however, did not change the fact that the main problem was these units were overweight and caused the poor brake performance and life.

In our quest for better brake life, we tested several brake retarders. An electromagnetic driveline retarder performed the best and helped improve this major issue.

In 1987, the department purchased a large group of Ford E-350 type III rescue units equipped with 6.9-liter diesel engines. Once again, the shop was faced with trucks that did not stop properly and had extremely short brake life. The maximum gross vehicle weight (GVW) listed on the door post sticker was 10,500 pounds; however, actual weight was closer to 12,000! This was a huge problem that also posed a great liability if there was an accident with injuries. These trucks came equipped with hydraulic brakes with discs on the front and drums on the rear. On the units with the shortest brake life, the front discs were only averaging between 3,000 and 4,000 miles and the rear between 7,000 and 9,000. There was nothing the factory could do about the problem, and we installed driveline retarders on all units. The trucks would actually stop within specified stopping distance, and brake life went to 12,000 to 15,000 miles on the front and 17,000 to 20,000 miles on the rear.

Alternator V-Belts

In 1994, the department purchased two 2,000-gallon tankers to replace aging units. One of the first issues to raise its ugly head was early failure of the alternator v-belts. These units were equipped with Detroit Diesel 8V92TA engines, and the alternator was driven off the accessory drive at the rear of the engine. Between the engine compartment and the alternator was a very small space that retained a lot of heat, and the belts would not even live long enough to make it between scheduled preventive maintenance. We basically had to change the belts in the field when they failed, which usually was called in as an “alternator not charging” complaint. The truck manufacturer and the alternator manufacturer basically just wanted us to make sure the belts were properly aligned and adjusted correctly, thinking this was the issue. Needless to say, this was not the issue, and to correct the problem we purchased accessory drive pulleys for 12-groove poly-v-groove belts and had custom ones machined for the alternator as they were not available. This resolved the issue, and this modification increased belt life to more than 20,000 miles.

Caliper Issues

Part of a large purchase the department made in 1982 and 1983 included 10 pumpers and 10 50-foot TeleSqurts®. These trucks had rear open cabs and were equipped with air disc brakes on the front and rear axle. Here again, brake life was very poor because of a major issue with the calipers. The calipers were mechanical with an internal S-cam mechanism that applied the brakes when the brake chambers were applied. Although the factory representatives examined the problems and provided training on rebuilding the calipers, they could not correct the problem. When the S-cams applied pressure to clamp the pads and apply the brakes, the cams would gradually score the bore of caliper, leaving a spiral groove. Over time, as the grooving became larger, this caused the cams to bind in the bore, and the pads would drag and wear out prematurely—not to mention failed brakes, ruined rotors, and severe brake fade.

Although the calipers were rebuilt and greased properly with special grease, there was nothing the factory could do to correct the problem, and eventually it stopped manufacturing the mechanical air disc brake system. What we ended up doing was removing the entire system and installing the Rockwell (now Meritor) air disc brake system. This was done with approval from Rockwell’s engineers and was very costly to modify. After a number of trucks were completed, we ran into an issue where Rockwell would no longer approve the brake modification. It appears a unit that had been converted in another state had been involved in a serious accident with injuries, and the result was Rockwell would no longer approve the retrofits.

A word of caution: Any modifications involving brakes or steering should always be done with engineering approval from the OEM or brake manufacturer. It must also have approval in writing from either the OEM or brake manufacturer. If not, liability can be very great in case of failure and would fall on the authority having jurisdiction and the department. Since we could no longer move forward with the retrofits, we opted to install driveline retarders on some of the remaining trucks, and others were either moved to the spare fleet or to slow stations.

Charging System Problem

Between 2007 and 2008, the department purchased 34 rescue trucks. Here again, the trucks showed up with a charging system problem so severe that the alternators were failing almost immediately after going into service. Some were failing as the crews were changing into their new unit! Diagnosis revealed that the alternator diodes were failing, and the main issue appeared to be excessive heat. The alternator was mounted in a tight area with virtually no air flow across it. The trucks were specified with 250-amp alternators with external rectification, yet these units showed up with internal bridge rectifiers. This was puzzling, and my further research discovered the factory had called a department representative in the Research and Development Bureau, explaining it had no way of mounting the specified alternator. The person it spoke with gave approval to mount internally rectified alternators. This proved to be a huge mistake. After studying the issue at the shop, we designed a mount that would adapt the originally specified unit and had a local machine shop fabricate it. The whole time the alternator manufacturer covered the failures under full warranty. The truck manufacturer agreed to cover the cost of the new alternator mounts, and the fleet was retrofitted with the correct alternators. The problem was resolved with the modification, and the alternators would provide years of trouble-free service.

I have had to spearhead modifying many different ERV systems that were either not performing well or were experiencing premature failure. These ranged from electrical system issues to brakes, steering, charging systems, hydraulic systems, engine cooling systems, air conditioning, and many others. Sometimes after exhausting all avenues to correct the issues, you have to come up with something to fix the problem on your own. Good, experienced technicians have proven many times to have the answers and ability to modify equipment as needed. When faced with these problems, use common sense and certified technicians, and remember to involve the OEM and manufacturer as much as possible, especially with safety-related systems such as brakes, steering, and aerial devices before performing modifications you deem necessary.


CHRISTIAN P. KOOP retired as the fleet manager for the Miami-Dade (FL) Fire Department after 35 years with Miami-Dade County and four years in the military. He has been involved in the repair and maintenance of autos, military track and wheeled vehicles, heavy equipment, and emergency response vehicles for the past 40 years. He is a member of the Fire Apparatus & Emergency Equipment Editorial Advisory Board. 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/medium/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 the Emergency Vehicle Technician Professional Qualifications.