Just installed a DPD A/C system (134a upgrade) on a newly rebuilt stock 1.7L D-jet (1972). A/C seems to be working fine (took a while to get charged) but really adds a load at idle. Have a new Sanden 508 compressor. Read a while back that someone had installed an idle "kick-up" switch as part of the D-jet system when compressor is on and car is at idle. Cannot find any details in a search.

Question, can one (or has anyone) devised an electric equivalent of the AAR such that it boost the idle only when the compressor is on and the car is idling? Right now I am having to set the idle (compessor off) at 1200-1300 and with compressor on it drops to around 600. Car wants to stall when start to pull away, just to much load to get going.

OR is there a way to automatically kill the compressor when the car is at idle with a relay that opens when the rpm drops. This may be the better solution as it would not put as much strain on the engine. I can live with the A/C off when car is at idle for short period of time. I have read that the Sanden's efficiency does not come into its own until above 1500 rpm anyway.

There has to be a simple fix.

Thanks
jjs3rd914

Sorry for the double post. Ignore this one. Do not know what happened.

Sorry.

jjs3rd914

Lots of cars have "idle kickers" that are electric. It would be a matter of how to mount it. Then just wire it to the compressor lead.

my thought (from someone who removed the a/c from a 914) is to use the cold start valve.... haven't done this but it's a fuel source that is controlled by an electrical input.. just a source of an idea.

I have found that the Sanden 508 is too much displacement for the DPD system. I have tried the 709 ,508 and I am now using the SD507 wich has been much more compatible. I now have a 200rpm drop from 1200rpm to 1000rpm on cycling of the compressor (carbs). A 600rpm drop on cycling of the compressor would show a overcharge, a restriction, or and over sized compressor. I have been using the SD507 for 6 month every day and I am now happy with the pressures and operation.

Interesting response. I have been led to believe the 508 was the ticket. Also I cannot imagine I have an overcharge as it barely took 2 cans (12oz). It will not take anymore. Actually each of the two cans are seem to be at least 1/3 full yet, so I suspect I have less than 20 oz of freon. Is that enough? The DPD manual said for R12 should be 2.2lbs. 80% for R134 would be in the mid 20 range. If I am undercharged (LP is at 30,HP at 180 which seems about right) how do I get more in if it will not take it. Been told not to turn can upside down? Also the LP lines are not getting that cold, vent temp is about 50. It was in the mid 70's yesterday here in Sarasota.

Thanks.
jjs3rd914.

I used a Denso 10P08E on my 904 kit car which use a 914 under dash unit.
I only have a 100 RPM drop when being used.

I had the same problm in my karmann ghia with AC.
what I did was buy a 12v pusher solenoid that I hooked up the the compressor
clutch circuit. I mounted the solenoid next to the accelerator linkage. I made the
bracket adjustible to I could slide it closer/further way from the linkage.
when the compressor came on, the solenoid would open and puch the acc
linkage a bit to raise the idle. it doesn't take much pressure on it to raise it a few 100rpm.

it worked well for me.

good luck!

Your TXV metering device sounds like it is stuck in the open position. I will respond with more information tomorrow.
SM914

If you are referring to the expansion valve, it is new and is for 134a. How much charge is normal for the DPD with 134a?

Thanks
jjsandsms

Before I responde to that ? My conserns are why with FI system is droping 600rpm . FI guys please respond. I will start a new A/C thread soon. With your pressures ( min. load, under charged) you should not have this type of rmp. drop. FI GUYS RESPOND !

I've been using a cold start valve off of a rabbit. It's Tee'd into the normal cold start valve and wired to the compressor clutch. The rabbit valve is somewhat adjustable but it's still too big so I put a reducer in the hose. It took a while to get the volume right but it has been working well for some time now.

Jjs3rd914 and Southernmost914,

Could you guys possibly post a description and maybe photos of the conversion to the Sanden rotary compressor from the the old style York reciprocating compressor. Did you use a kit or do it yourself. Any info would be appreciated.

By the way I made a trip in my 914 to Key West in the early 90's! Woo-Hoo!

Click to view attachmentI opted not use a idler pulley. DPD "L" bracket wich bolts to the fan housing and a standard York to Sanden adapter bracket ( ebay, bus depot, ect). Many ways to do it, this is just mine.

I'll be installing my a/c this winter (in prep for next summer)....

I would appreciate knowing the source / part numbers for the expansion valve / belt length / any other shots of installs.

I made my own mount from the Sanden to York adapter plate. Modified it to mount directly when the York mount used to go on the fan housing. Machined some standoffs for adjustment and it aligns wells. Had to trial and error fit the fan belt length.

jjs3rd914

Click to view attachment
Click to view attachment