Tampa 928s

Got the air all working nice and cold after I went to the air place to get the R-134 properly weighed due to a small leak repaired .
This is the second Reciver dryer installed the first one would leak or say blow out R-134 due to a bad schreader valve. Replaced it with a new one same thing get it all charged up removed the high pressure gauge and boom
I thought it was my gauge that was having an issue so "see above", the air place did a R-134 removal weighed it and put it back in all was right with the world. He removed the high pressure gauge boom Changed the valve, boom again so he just replaced the R-134 cause we knew it was ok except for that valve, or so we thought.
Long story sorry, got it home spent the last two days replacing the wiper motor, window switches and reparing the rear hatch release. I washed and went for a drive, nice cool air drove great and stopped by the VW dealer to pick up an inj cap for my TDI. Would you not know it the salesman were hanging aroung I started the car and was setting my radio stations and see smoke shooting from under the hood.
The high pressure Reciver dryer valve blew its top. I mean blew the red cap in 1/2 never found the piece.
What happened the Air shop screwed the cap on to tight or the wrong cap which pressed down on the valve therefor allow the pressure to release. Not a problem but for a small leak but once I shut the car off the pressure build up launched the cap like the space shuttle.
Can anyone beat that ?

dr bob

R-134a has a nasty high-temp pressure spike compared to R-12. That's a big reason why I hesitate to recommend the conversion for pre-S4 cars. It would be OK if you have redundant electric fans. Otherwise, you need a late pressure switch and plug, so that either high- or low-pressure situations will cut the current to the compressor clutch. There are some horror stories like yours, and more with the drier safety plug blowing out.

So, whadya got for fans and fan switching?

Tampa 928s

I have the factory front fan that cuts in around 280 Lb's but not when car is stopped. Seems like the newer years had this feature, I should get a relay or change over to turn the fan on after the car stops. Any parts list or a way to point me!

Tampa 928s

Looking for posts on adding a relay for turning on the fan while A/C is on not a big deal. Question is there a set up to allow the fan to run a little bit after car is stopped, I'm in florida and this seems to be a good idea with using R-134.

dr bob

The big issue won't be after the car has stopped, unless there's a huge amount of heat migration from the radiator to the condenser... That won't happen.

I'd be looking seriously at one of the better electric fan options, like the multiple fans kits that some of the guys like Carl sell. Airflow through the condenser, serious airflow, is your best chance at survival with R-134a. The better kits have the fans come on based on engine temps sopmewhere just north of thermostat temp, which should be in the 195f range. Power should go through a temp switch o a relay (or two...) to run the fans. You can add the signal from the compressor clutch, through an isolation diode, to the relay coil. Add a diode to the temp switch signal too, for safety. Then whenever the AC compressor is running, the fans will also be running.

The early cars really depend a lot on the properly-functioning belt-driven fan and thermo clutch for most of their cooling. Many of those are not as robust as they once were. The silicone fluid leaks out of the clutch over time. More often, when the unit is removed for some engine service, it is 'stored' in a horizontal position arther than standing up as it is when installed. There are some refill procedure posted at a few of the tips pages, showing how you can refill the clutch using some Toyota fluid. There's no good way to test the function of the clutch, other than watching the engine coolant temp. I guess if I had a pre-S4 car, I'd pull the fan and clutch and refill it no matter what; It's cheap insurance.

Tampa 928s

Dr Bob

I am hooking up two relays as we speak what are you saying about a diode, put it in series with the signal from the compressor relay from the control unit? I am following a post on this but did not mention the diode.

dr bob

Yeah-- A couple diodes will isolate the trigger signals from each other. Without a diode in the compressor line, for instance, a signal though the temp switch would activate the compressor. Of course, the less-than-elegant way is to just use two relays I guess. More to the point though, the original fan relay will work with this simple addition, something that net makes the project a little easier. The compressor trigger already passes into the CE panel and back out, at least on my S4, so adding a diode and a little wire would be a snap if your compressor wiring passes through there as mine does.

Tampa 928s

I used two relays one for the compresser and one for the fan.
I did test it with 12v and it all works, for now I am doing a vacuum for a couple of hours and will get it charged this week.

Tampa 928s

This was the post!
able to post diagram from my scanner so I'll type it:

1.) Interrupt wire from AC control head to compressor (located near top PS timing belt cover)
2.) Disconnect refrigerant temp switch on top receiver drier. This leaves two wires available one is a ground one is from AC fan relay.
3.) Add two new generic SPST relays. Connect as follows:

RELAY I: 85 from AC control head
86 to ground
30 to 12V at jump post via 10 amp fuse
87 to AC compressor clutch

RELAY II: 85 from AC control head
86 to ground
30 to ground
87 to AC fan relay (striped wire from disconnected refrig temp sw.)

I will let the air guy take care of this because he caused it to launch in the first place.

dr bob

I'm sure the two-relays method will work fine. It's simple and will be easy to troubleshood should problems arise in the future.

I'm on the kick of doing the least amount of "add-on" stuff in the electrical system. Some things, like the AC control head relay, are unavoidable. Others, like this fan 'fix', can go either way. In the end, go with what you are comfortable doing and owning. For sure, a Tampa summer car deserves the most expedient solution that works. 2 Relays it is for you!

Stay cool!

Alan

One thought - its nice if the fans don't come on during starting... not normally a major issue - but if you have wired to have them on anytime the AC is on - you may now have dual fans and AC clutch on with the starter -even when 'cold'. This is a lot of extra current in addition to the starter.

Ideally the AC clutch would be disabled during starting also...

Alan

Tampa 928s

I always turn the A/c off when I stop the car so should not be an issue!
The relays are connected to the a/c control head so this should not be an issue when starting or am I missing something as usual?