A/C and heater problems

1974 CADILLAC ELDORADO

56,300 MILES • 8.0L • V8 • 2WD • AUTOMATIC

CADDY74

MEMBER
5 POSTS

A/C doesn't blow cold air. Heater blows hot air constantly when car is on or when engine is running will not stop even when A/C is on. A/C shop Evacuated r12 from A/C system changed fittings and recharged with r134. Cold air for a few days then it stopped.

Jun 16, 2019 at 9:55 AM

STEVE W.

✓Experienced Mechanic
15,382 POSTS

Welcome to 2CarPros. The description sounds like the A/C has a leak. R134A has a smaller molecule size than R-12 and will even leak through the hoses. I would start by checking with a set of gauges to see if there is any charge in the system. Then recover and vacuum the system down and see if it holds. If not then you will need to repair whatever is leaking.

Jun 16, 2019 at 6:33 PM

CADDY74

MEMBER
5 POSTS

Thank you. I will check everything on Monday 6/17/19.

Jun 16, 2019 at 7:59 PM

STEVE W.

✓Experienced Mechanic
15,382 POSTS

A common issue with retrofits like this unfortunately. There is still R-12 out there but finding a shop to do a full flush and recharge can be expensive. Another thing to check would be the heater control valves to be sure the heater core air is being stopped. I have added bypass valves on some of the older vehicles to help the A/C work better by diverting the hot water so it doesn't go through the heater core when you turn the temperature to cold and A/C.

Jun 16, 2019 at 8:42 PM

CADDY74