911tracker85

I suspect I need to replace the heater control valve on an 87 944S 16V, or I have some major vacuum issue that is not effecting the engine running. common symptom, always HOT. I have already checked the flappy control in the footwell.

but so far I cannot find it down under the intake where the WSM says it should be.

the 16V has a very different intake and occupies a lot of the space where all the docs I have read say it should be.

looked in WSM, read Clarks garage writeup, PET.

anyone know where it is located?


searched threads but cannot find.

Jfrahm

It's by the oil filter. I have had them pass coolant when they otherwise appear to be OK, resulting in heat all the time. Replaced with the Audi 5000 / Escort style valve which I prefer.

ernie9468

Location of HCV on my 968,should be the same on your car since both are 16V models.

911tracker85

thanks, found it where you said.

checked with mightyvac and the valve closes. in the middle of something so cannot start the engine to see if heat stops with a zip tie on the valve.

traced the vacuum line and it goes to a connection on the firewall. starting to fear it is the HVAC module inside the dash.

in the process of checking this, when moving the PS reservoir to get to it, one of the hoses started leaking bad. I was planning to replace as the hoses were clearly ready to rupture.

and then when tinkering with the heater valve, slightly bumped the elec connector just above it and the connector just shattered. wire on part that shattered leads into the cam belt cover. don't know what it is yet.

Arominus

That is the connection for the Hall effect sensor, you need to zip tie that guy back up so it stays away from the exhaust. On my car that wire slipped down towards the header and when it got hot the car would not run. That sensor tells the DME where the camshaft is in its rotation.

Jfrahm

If that valve is old you should replace it before it splits and dumps coolant on your RF tire. Plus, I have seen them pass hot coolant while appearing to work properly resulting in constant heat.

911tracker85

found the cracked wire connector is from the Hall sensor on PET. there is a wire coming up from below with a female connector to a little metal tab/holder, and the male connector goes into the cam belt cover.



both connectors were being held by the metal tab/holder up and away from the head. no idea yet where the wire going down towards the headers eventually goes. that isn't my problem.

by just bumping with my hand against the connector caused the side of the plastic fitting to crack off. it was the male connector going to the Hall sensor that cracked into several pieces. so now I know what I need.

regarding the heater control valve. clearly it has been replaced, along with newer clamps and hose sections. but until I resolve the Hall sensor issue and get the engine running again, cannot tell if forcing the valve closed stops the interior heat.

I was able to test the valve creating vacuum with my mightyvac. I need to get a little gauge to test vacuum the car is generating for such troubleshooting.

just finished talking to Chuck and Jason at Paragon, more parts on the way.

FRporscheman

On both 968s I've had, the hall sensor harness has disintegrated. I got an identical 3-terminal plug off of a VW at a local junkyard for a few bucks, I cut off the old broken plug from the Porsche's wiring, and spliced the new plug in with solder and heatshrink. It's a bit of work, but way cheaper than a new sensor, and actually it might be less work than replacing the sensor.

+1 on the Audi 5000 all-metal HCV.

911tracker85

^^^PM sent.

I have epoxied the parts together, but have not been back to the shop to check/test.

911tracker85

got back to the shop. when trying to plug in the 'repaired' connector, it just broke into more pieces.

so cut it off and spliced the Hall sensor wiring and the car is running again.

so checked the HCV by zip tying it closed and the hot air stopped coming through the vents. and could not feel any vacuum on the line coming from the firewall. so guess it must be either the HVAC control in the dash or some leak in the dash.

my next question is does a failure of the HVAC control in the dash also tend to effect running the AC?

we can live with the zip tied HCV for the summer, but must have AC.

really don't want to take the time right now and rip out the dash.

thoughts?

Arominus

Follow the vac supply from its start at the brake booster, there is a valve there that it hooks up too, then to goes over to a plastic canister by the battery. From there it goes to the firewall and into the car. You shouldn't need to pull the dash.

Arominus

Here's a few pics of what to look at.

16valver

I don't know if anyone has touched on this:

I had the same issue this summer with the hot blow. What I did was pop out the glove box which will expose the side of the HVAC system. There is a second heater valve right there with a couple lines going to it. Its more of a box shaped thing. I don't think I have pictures but I'm sure they aren't hard to find. I disconnected those lines to check and make sure they held pressure and weren't leaking. Upon disconnecting what looked like the main line, there was a hiss as some built up pressure was let out. I reconnected it, took the car out for a drive and voila!!! No more hot blow!!! I'm not sure what I did but I would think the system pressurized wrong somehow which led to the heat always being on.

I learned that sometimes this system will go in to limp-mode and will by default blow hot air in case you are in a very cold place.

I'll try and find a picture of what I'm talking about. Its not hard to find, though.

911tracker85

thanks for the ideas and pics.

Arominus.
I will need to trace the line from the HCV again. when I traced it looked like it went under the intake back to the firewall and over to a connector on the firewall below the battery. was in a bunch of other wires/lines at the firewall so may have to cut the zip ties to really see where it goes.

16valver.
I was hoping by pulling the glove box I may be able to see/access some of the HVAC stuff in the dash, and hoping to find where the vacuum line comes in from the firewall.

from all the HCV threads I read, it sounded like the last item that would be the cause of this problem is the HVAC control module in the dash.

glad to get replies from both of you as it seems like everything on a 944S is 'just a little different'.

for example, when replacing the PS reservoir and hose, noticed a connector to the bottom of the PS pump. when looking noticed it only had one connector in tact and the wire was just bunched and zip tied together and the other end not connected to anything. from research it appears this was only done on 944S to trigger the PS to work a bit harder when the AC was on.

despite the differences with the S, looking forward to extra 30hp.

speaking of burnouts.... the guy I rent the garage from has an older Corvette he built to take to the track. very built 355 with ~450hp, headers, side-pipes. fired is up this past weekend, checked it over and once warmed up he pulled into the street and laid down over 50ft of rubber without trying hard.

911tracker85

Arominus

reading your post and looking at the pics further. are you referencing the vacuum line that goes to the HVAC control? it would need vacuum, and then depending on the HVAC temp setting would allow the proper level of vacuum to the HCV? I tried to track the line from the HCV to the source of vacuum and think it goes to the firewall.

thanks again for the replies. if not for Rennlist and Pelican forums I would have never been able to learn to wrench on any of my Porsches.

wont get back to wrenching until Thurs. have to catch up on 'honey do's' evenings this week.