Hello all!

I'm a new member who just purchased my first 1988 928 S4 a week ago in Grand Prix White over Red (Can Can?) Leather with automatic transmission. The car has 66k miles and I bought it from the Detroit area and drove it home to the St. Louis area earlier this week. The car did great on its first big road trip and I appreciated the comfortable seats for the journey. The unique color combo and maintenance history on this car really won me over as compared to a local one I was also considering. While I'm new to Porsche ownership, I've been a long term owner of a Euro-spec 1984 BMW 635CSi and am really enjoying learning about the similarities and differences between the two Grand Touring 'Sharks'.

I've been lurking over the last few weeks prior to purchase and trying to absorb as much knowledge as possible. Even so, forgive me if I have some newbie questions along the way.

My most pressing issue at the moment is that I'm getting full heat inside the cabin with no temperature regulation for the front vents. I installed a new heater valve on Friday and while the one I replaced was visibly damaged, I can't feel any improvement with the new part. Any ideas of where to troubleshoot next would be appreciated.

I've also installed refurbished Cup 1 wheels and new Continental DWS tires for an immediate upgrade from the chrome manhole covers it came with along with old rubber. Waiting on new center caps to arrive in the mail for them to look complete.

I've made an introductory video of the car on YouTube if you'd like to see a little more of the car in walkaround form:
Looking forward to joining the fray and interacting with everyone more soon!

 

Exceptionally clean car! Great find!

Congratulations and Wellcome to the Shark Tank...

 

Love it, very nice!

I'll admit I'm a bit biased as I have a Black/CanCan S4.

 

Gorgeous car. Welcome! As to your heat issue, one thing that can impact cabin heat is a deteriorated insulation shield in the shift area, under the shift plate. What happens is the insulation deteriorates, and couple with old motor mounts, which cause the whole shaft to drop a bit, a space in that area is created and the engine heat comes up through the tunnel into the cabin. You can check by carefully removing the shift plate (these is an instruction in the WSM, or search this site), and look at the insulation. On one of my prior cars, I added pink insulation into that space and it cured the heat issue into the cabin. The real fix is to do the motor mounts, and drop the torque tube and replace the insulation. Pink insulation works fine until then though.

Of course, you may have something else going on. This is just one item that could be the issue.

 

Climate control troubleshooting can get involved. Search this site for tips.
Does airflow change with defrost vs high/low vs auto?
If not, could be a lack of vacuum to the controller or serious vacuum leaks.
Could also be a bad cabin temp sensor or a fault control or bad solenoid valve or bad vacuum hose or bad vacuum diaphragms.
If airflow changes but not temp, still could be almost all of the above, minus total lack of vacuum.
Good luck

 

I guess its cold in Europe, so Porsche thinks the safe failure mode for the climate system is full heat. So many failures will result in full heat, and one I have seen specifically is a vacuum hose pulled off or broken. Basically the hot water control valve is open by default, and if you don't get vacuum to it it will be open and you will get heat. So, follow the vacuum line from the hot water valve you just installed and hopefully there is just a hose off somewhere. There are several places where they line transitions for hard line to soft line and sometimes it just comes off at the transition.

 

Thanks! Do we need a dedicated Can Can pics thread? Does yours have the red carpet too or is it a 'partial' Can Can like mine?

 

Yes, I should've mentioned the defrost mode works correctly and the venting of air will change when moved to that mode. Also, the rear A/C works and blows cold with the front A/C switch turned on, and rear fan turned on - but I get no cold air from the front A/C with switch on. I'll explore further.

 

Good idea, I inspected the end of the vaccuum hose that I reattached to the valve and it appeared in good shape, but I can trace it back and examine it further.

 

 

Post script on the pink insulation - make sure you tuck it in tight, and don't use the fiber glass type - if the particles blow out, you'll be sorry.

 

Welcome. That's a very nice one.

You've found out how well they do on long road trips. It's what they were made for.

Regarding the heat issue:

Does it blow full hot on every setting except 'full cold' (far left)?

There's a weird failure mode where when the outside temp sensor fails or is disconnected, it does that.

That temp sensor is located inside the alternator cooling hose, in front of the driver's side wheel well liner.

On mine, it did just that - full heat unless the slider was all the way to the left.
It turned out the plug wasn't making good connection. Pulling it apart and blasting it with DeOxit fixed it.

 

I'm even getting full hot at the far left setting! So I'm guessing it's something else based on that.

 

How about that. Gotta love when the fix is something free, easy, and due to user error. The reason I was still getting full heat after the new heater valve install is I neglected to attach the hose under the air box that I assume feeds the vacuum system. I took everything back apart today and the issue became easily clear.

Thanks for all the help with my first rookie mistake! I have working A/C and fresh air now and don't have to drive around in full sauna mode anymore lol.

 

Congrats! She looks clean and orginal. Just in time for your next road trip and come on down to 3rd Coast https://rennlist.com/forums/928-foru...-8-2020-a.html