This from Bill Post:

Here is the information that I have so far on the  “Heat Wave Ambulances.”
From my sources, the CFD started making plans to put them in service on July 3rd due to the high heat forecast, so I assume that they were put in service on July 4th. They were taken out of service at 6 am Sunday morning July 8th 2012.
I’m told that Ambulances 70 and 71 are now  being used for the Presidential Motorcade Detail when the President is in town.
There were a total of 10 ambulances that were in service.  They were numbered from 67 to 69 and from 72 through 79. There were no ambulances 70 and 71 involved in the heat emergency and for the first few days there wasn’t an Ambulance 75, which was having mechanical issues. On Saturday when Ambulance 75 did go in service, it just replaced Ambulance 79 at Engine 63’s house which was taken out of service.
The Heat Emergency Ambulances were:
Ambulance 67 at Engine 44
Ambulance 68 at Engine 112
Ambulance 69 at Engine 79
Ambulance 72 at Engine 38
Ambulance 73 at Engine 35
Ambulance 74 at Engine 23
Ambulance 75 at Engine 63 (on Saturday as the first days had been out of service)
Ambulance 76 at Engine 88
Ambulance 77 at Engine 109
Ambulance 78 at Engine 121
Ambulance 79 at Engine 63 (until Saturday when it was replaced by Ambulance 75)

Readers should feel free to ad any relevant additional information. Most of the Heat Emergency Ambulances were out on the streets involved in “District Familiarization” when not on actual runs or on special details.

On  Friday morning, Ambulance 69 was detailed to standby outside the Church at 832 N Leclaire, where the funeral was held for the 7 year-old girl who was shot to death by a “gang banger” thug  in front of her home while selling lemonade the previous week.
Several cooling buses from the CTA were called for by CFD paramedics on the scene of the funeral  service to accommodate the large crowds people.