PHOENIX -- When Richard Henley called 911, he never expected to be transported to the hospital in a fire truck.

Surprise Fire Captain Jerry Clark and Medic/Firefighter Arthur Casillas found Henley, 78, struggling when the fire crew arrived.

"He needed to get into the hospital," Casillas said. "He needed some help."

After 13 minutes of waiting for an ambulance, Clark called dispatch to check on its status.

"I called back to the alarm room (and) asked them to check what the ETA on the ambulance was," Clark said. "Probably another minute to two minutes after that they responded back, stating Southwest hadn't dispatched an ambulance yet."

Clark decided to use the fire truck to take Henley to the hospital.

During a five-month investigation into Southwest Ambulance, which provides ambulatory services throughout the state, 5 Investigates uncovered troubling response times, medics who said they are pushed to the limit, ambulances in various states of disrepair and expired supplies.

• Read: Southwest Ambulance Responds To Investigation (.pdf)

Surprise Fire Chief Michael White said he noticed a problem with Southwest's response times more than a year ago.

A 15-minute response time is not acceptable, he said.

The state of Arizona requires ambulance providers to respond to calls in less than 10 minutes 90 percent of the time, but some dispute when the clock starts.

Southwest times from the moment the call comes in to their dispatch. By its own calculations, the company only hit the 10-minute mark in Surprise 77 percent of the time over a six-month period.

The Surprise Fire Department says it has tougher standards -- the clock starts when the call comes into 911. In that case, Southwest meets requirements the requirements in Surprise only 51 percent of the time, and sometimes takes as long as 40 minutes to respond to some calls.

One Southwest medic, who requested anonymity, said ambulance crews now sit on street corners across the west Valley to wait for calls, just to lower response times.

After an analysis of data on response times, 5 Investigates found the practice did lower response times by about one minute.

The medic said the practice has affected medics -- especially when an ambulance's air conditioner is broken.

"I know one guy who passed out -- whose blood pressure went down," the source told 5 Investigates. "Myself, I felt very nauseated at the end of the day. (I'm) just drinking literally a gallon of water throughout the day just trying to stay hydrated."

Jeff Sargent, the president of Southwest Ambulance, said he was unaware of any incidents in which a medic got sick because of a broken air conditioner.

Additionally, 5 Investigates discovered that more than half of Southwest's ambulances are either broken, missing life-saving equipment or have expired supplies.

According to Sargent, if an ambulance breaks, the rig is repaired right away at the fleet center.

5 Investigates, however, checked maintenance records and found ambulances on the road with broken emergency lights, sirens that don't work and nonfunctioning horns.

Additionally, out of the 170 Southwest ambulances inspected in 2008, 69 have more than 300,000 miles on them. Ten have been on the road for more than 400,000 miles.

Another Southwest medic, who also wished to remain anonymous, explained, "That's not cruising miles on the freeway. That's jamming it to the floor to code three to take someone who's dying -- stomping on the brakes, jamming it to the floor, moving in and out of traffic.

"Those are hard, beat-up miles," the medic said.

The medic added, "Would you buy a personal vehicle with a half-million miles on it to take your sick family member to the hospital? No."

Sargent said it's not unusual for an ambulance to have that many miles on it.

The investigation also found that not all of the ambulances had proper life-saving equipment, such as oxygen tanks. Other ambulances were stocked with expired medical equipment like IVs, breathing tubes and blood glucose testing kits.

5 Investigates also discovered expired drug boxes -- one dating back to 2006.

The two medics who spoke with CBS 5 News said the drugs are also improperly stored, leading to overheating.

"We brought a thermometer in one day and left it in the back of the ambulance during the hottest part of the day with the air conditioner running," the first medic said. "It was 102 degrees."

According to the instructions on the drug boxes, the medications should be stored at room temperature.

"There's nothing protecting those drugs," the second medic said. "Heat affects all things."

Sargent said if the medications are being stored in extreme temperature, that could damage them.

The Arizona Department of Health licenses ambulance providers; however, it only checks response times every three years.

In fact, the department said it did not know Southwest was not meeting response times in Surprise until 5 Investigates showed it the results of the investigation.

The Department of Health said it will review its policies.