A/C Question

prideclaw · May 30, 2004

Can anyone here tell me where the fuse or breaker is on an A/C compressor of a 1885 Chevy Silverado( if there even is one)?

I know the fuse box on under the dash has the fuse for the HTG/AC system,but I mean the compressor itself.

Thanks

snoman · May 30, 2004

Not that I am aware of. If it will not turn on it may be low on freon as there is a limit switch that prevents the compressor from running if low on freon.

prideclaw · May 30, 2004

Thanks snoman.I did bypass the low pressure switch but the clutch didn't engage.I had checked the fuse under the dash(OK) but I don't think that it directly protects the compressor.The problem was that I didn't have a DC meter with me to check for volts at the clutch.Just wondering if anything was directly protecting the compressor itself.

snoman · May 31, 2004

There may be a high pressure cut out switch too. I am not sure what year GM started that though. It seems logical that it would have its own fuse but I have never seen one. If they is one it is probaly a inline design or fusable link.

prideclaw · May 31, 2004

Thanks again.I was thinking the same thing in that there has to be some sort of inline fuse.

prideclaw · May 31, 2004

If there is a HP switch it must be bad.The static on the system is down to 20 psi.I'll probably just run a wire from the hot post to the clutch tomorrow to see if it pulls in and then Ill work my way back from there

prideclaw · May 31, 2004

And I do know that alot of newer cars now utilize fan cycling switches on the liquid line in electric fan applications so there wouldnt be one here('85 4.3. . fan clutch)

Mighty HD · May 31, 2004

Can anyone here tell me where the fuse or breaker is on an A/C compressor of a 1885 Chevy Silverado( if there even is one)?
I know the fuse box on under the dash has the fuse for the HTG/AC system,but I mean the compressor itself.

Thanks

That's an Oooollllddd chebby!

snoman · May 31, 2004

If there is a HP switch it must be bad.The static on the system is down to 20 psi.I'll probably just run a wire from the hot post to the clutch tomorrow to see if it pulls in and then Ill work my way back from there

If you have 20psi static on your system you are out of freon and low pressure cut out is protecting compressor. Static pressure should be 90 to 150 psi depending on ouside temp and engine compartment temp.

prideclaw · May 31, 2004

There-in lies the question.I've already by-passed the LP switch but the compressor still didn't start.But I do appreciate your help.

snoman · May 31, 2004

There-in lies the question.I've already by-passed the LP switch but the compressor still didn't start.But I do appreciate your help.

You do not want to try to start it either with 20 psi static as the compressor will not be lubed and cooled properly. Confirm manual operation of clutch with a hot wire jumber (engine does not need to be on) and if clutch is good, install some freon in system (if you have some R12) to get pressure up and see if system works then. I would advise against a R134 conversion not only because it cools less but it develops more pressure than a R12 compressor was design for, I would suggest Dupont MP 52 ( a mixture of R22, R152a and R124 that closely matches R12 presure curve and cooling capacity and is compatble with existing oil in system too) or R12a with a really a hydro carbon based gas the mimicks R12 real good and will greatly outperform R134 in a old systems and has zero enviromental impact unlike even R134a. Two cents worth anyway.

prideclaw · May 31, 2004

Thanks for your help.Unfortunately the conversion bridge has already been crossed.

prideclaw · May 31, 2004

I've personally had VERY good results from AZ-20(formerly RB-276) as a direct replacement for R-12.Although I never used it for a direct R-134A replacement,AZ-20 does contain an visible additive that neutralizes both Mineral AND POE oils.It's what I have had in my 93 S10 for 4 years now. Outstanding temperature glide in relation to R-12 or 134-A

snoman · May 31, 2004

I've personally had VERY good results from AZ-20(formerly RB-276) as a direct replacement for R-12.Although I never used it for a direct R-134A replacement,AZ-20 does contain an visible additive that neutralizes both Mineral AND POE oils.It's what I have had in my 93 S10 for 4 years now. Outstanding temperature glide in relation to R-12 or 134-A

According to what I just read now AZ-20 and RB 276 are two different products. AZ-20 (also know as 410a) is a replacement for R22 but it does not list it makeup. RB-276 is a combo of 79% R134a and 19% R142b. Using a freon replacement that is about 80% R134 in a R12 system is not a great solution. At least Dupont MP 52 contains no R134 in it!