What's this item on the a/c dryer?

[mytrplseven]

I can't find any electric diagrams for the a/c system to verify what this is and how it's wired into the 1986 944. The low pressure switch is below it. Supposedly the diagrams are in Volume 4 of the 944 workshop manual but I can't find a link for it. If anyone can help here, I'd appreciate it.

[Dimi 944]

Should be the pressure sensor/ switch.

Dimi P
Flying Horse Motorsport LLC
flyinghorsemotorsport@gmail.com

[9FF]

It’s part of the radiator fan circuit, when the ac refrigerant gets to a certain temperature (measured as pressure), it turns both radiator fans on by sending a signal to the fan relay.

[djnolan]

Thank you for posting this, I always wondered how this circuit worked. It looks like it is paired with the high speed fan circuit as it is paired with the 102 degree side of the coolant temp sensor.

Slightly off topic here: For anyone who thought the fans would be triggered by the snowflake switch and might want to test the fans this way, you would need a charged and working A/C. Or need jumper one of the sensors to test the fans.

[9FF]

Originally Posted by djnolan

...It looks like it is paired with the high speed fan circuit as it is paired with the 102 degree side of the coolant temp sensor...

Yes, either a high coolant or refrigerant temperature will send a signal to the fan relay to bypass the low speed resistors and turn both fans on full. The snowflake sends a signal to the fan relay AC terminal. This might help:

Coolant Fan Relay (G10)
X​ ignition -- on=12V off=0V
TF​ temp fast -- on=0V off=float
TS​ temp slow -- on=0V off=float
AC​ air conditioning -- on=12V off=0V
31​ ground
30M1​ fused 12V 25A
30M2​ fused 12V 25A
M1​ cooling fan 1 high speed
M2​ cooling fan 2 high speed
V1​ cooling fan 1 low speed (via external resistor)
V2​ cooling fan 2 low speed (via external resistor)

[mytrplseven]

I still need a wiring diagram for the '86 944 HVAC system. Help please.

[9FF]

Originally Posted by mytrplseven

I still need a wiring diagram for the '86 944 HVAC system. Help please.

The wiring diagrams are all in the workshop manuals and are quite detailed on the HVAC system.

[mytrplseven]

I finally have the diagram sheet I requested. I just don't have a set of 944 manuals to reference.

[9FF]

Originally Posted by mytrplseven

I finally have the diagram sheet I requested. I just don't have a set of 944 manuals to reference.

Ah ok, but quite honestly how are you working on these cars without any manuals?

First thing I got, they are available free online, places to download them from vary but you shouldn’t have to search long to get all six volumes in a pdf download.

If you have problems finding them for download just pm me and I’ll share mine.

[mytrplseven]

Thanks for the offer. I've been able to down load particular diagrams online but this one only seem to show up for 1988 and later. Right now, I've posted a question about the G10 relay. if you have anything to offer, it would be welcome.

[djnolan]

The electrical manual has two volumes "Vol4-electrical" is for 83-87 and "Vol5-electrical" is for 88-91 and are both easily found with google.

[9FF]

Originally Posted by mytrplseven

...I've posted a question about the G10 relay. if you have anything to offer, it would be welcome.

The G10 relay has nothing to do with the AC not working, the AC system controls G10 not the other way around, so you can literally remove G10 and the AC system will still function, albeit without over-temp protection.

This must be frustrating. Can you provide the exact issue you are having and what you’ve done so far, maybe collective minds here can assist.

[djnolan]

Have you seen this: 944 HVAC Operation and Malfunctions

[mytrplseven]

I was thinking that it was the situation but since I can't find a way to verify the A/C switch is working, I was looking at other obscure ideas.

[mytrplseven]

I did that early on but it doesn't seem to help with a/c issues.

[djnolan]

I haven't experienced it myself but these posts appear to go beyond Clarks with this issue:

https://rennlist.com/forums/924-931-944-951-968-forum/815094-a-c-compressor-not-turning-on.html

https://rennlist.com/forums/928-forum/586823-full-charge-but-a-c-compressor-won-t-turn-on.html

[mytrplseven]

Interesting that nobody was able to answer the question, "Where is the Icing Protection Switch"?
Thanks for the links to the similar problem.

[9FF]

Originally Posted by mytrplseven

Interesting that nobody was able to answer the question, "Where is the Icing Protection Switch"?
Thanks for the links to the similar problem.

I answered on your other thread.

[Stoneguy]

I believe the 2 sensors near the drier are low and high pressure sensor switches.
the green upper one is low pressure and the lower one is high pressure.
(Thats what is says in the PET)
the icing protection switch is on the right side of the blower housing

[Stoneguy]

Porsche 944 Air Conditioning

Some good info