BackInBlack

OK..so I recently had my A/C gone through. They replaced the compresor and drier, converting to R134. There was some issue with the clutch not getting power and they "fixed" it at the relay box (specifics unknown to me).

Friday I decided to try the A/C while tooling down the highway. Engine performance went away with a distinct surging. It felt like the spark became weak and I noticed a spike and lower reading on the volt gauge. PO had replaced the alternator recently before purchase. The reading is generally low (less then 13v) while driving, but I attributed that to some drop before the gauge or gauge itself. I can certainly put a volt meter on the bat to verify a reasonable charging voltage.

I'll be taking it back to the shop, but thought I'd check in here. Any ideas as to what would cause the surging and performance issue with A/C on?

'86 951 chipped

Spidey944

The A/C clutch puts a high load on the engine, so when it cycles, you will feel a "surge" as you put it. If it is cycling fast, then your A/C charge is too low and the compressor is working harder to make up for it.

Cone_eater

You lose a ton of power when you turn on the AC. No matter what its gonna happen.

N/a 944

Hooray for a loss of power.
It's over 105*f here from early may to early october!

+1 for the A/C pump cycling on and off. ESPECIALLY if it is low on refrigerant.

BackInBlack

Yes..it does seem to be cycling very fast (like every couple seconds). Doesn't get very cold either as a result. Back to the shop. I suspect it sprung a leak they didn't find during the conversion.

Should there be a idle kick-up when the compressor engages? If the engine is cold at idle, the compressor load kills the engine. Once warmed up it drags it down, but doesn't kill it. Should there be a similar idle kick-up for when the engine is cold (no A/C). It idles pretty low and rough when engine is cold (rather warm ambient).

Warm and no A/C it runs like a raped ape.

I tested voltage at battery. 13.6 running with no A/C. Engage the A/C and voltage drops to about 13.2 (idle). The gauge on the dash reads about 1 volt lower.

jns

R134 runs at a higher pressure than R12 so that may be a contributing factor to the engine drag.