Both vehicles were taken off the road for repairs for more than 12 hours while the vital navigation equipment was replaced.
Mersey regional ambulance service says the thieves are putting lives at risk and, if the spree continues, it will cost thousands of pounds to replace equipment.
Thieves are also targeting car drivers with satnav systems.
A hooded gang smashed into Lisa Courtney's car as she waited at traffic lights on the junction of Liverpool Road and Prescot Road in Page Moss.
Ms Courtney, an educational support worker, said: "It was in the middle of the afternoon, with lots of traffic waiting at the lights.
"It was frightening and glass flew into the car and landed in my 13-month-old baby's seat.
"Thankfully, she wasn't with me or she could have been seriously hurt."
There has been an increase in satellite navigation system thefts since Christmas.
Most sought-after are the Road Angel or Tom Tom versions, which are portable and clip into a cradle on the dashboard.
A police spokeswoman said: "It is extremely unusual for these thefts to take place when someone is sitting in the vehicle."
Yesterday, the ECHO reported the ambulance carrying injured Manchester United midfielder Alan Smith from Anfield was attacked.
Yobs pelted the vehicle with bottles and bricks near the King Harry pub on Saturday.
* Anyone with information on the thefts should contact CrimeStoppers on 0800 555111.
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