97 850 GLT - PTC diagnosis?

[Henry10]

PTC nipple is a dual-function device:

1- It is a PTC heater. PTC principles were discovered by French scientist Marie Curie, and PTC heaters are very good at constricted areas. Volvo PTC Heater device a- vaporizes moisture that is returned from the crankcase where car is driven in very cold weather. b- it also heats the incoming air. The warmer the air from crankcase/intake, the less this devices heats (due to the PTC principles). PTC is controlled by the ECU, which grounds it (i.e. puts it to work) when certain conditions are met (MAF flow, ECT, RPM, etc). In other words, ECU detects the conditions, and it allows the PTC heater to do its job.

If the PTC heater is not functioning well, this leads to intercooler and throttle icing. This guy in Edmonton, Canada is replacing his intercoolor because it gets frozen solid http://volvoforums.com/forum/showthread.php?t=51128. People ask -- what about cars in warmer climates? PTC does not do anything in this climate, except function 2 below.

2- PTC nipple is also the PCV valve. This is the heart of the PCV system in our turbo Volvos. Like any regular PCV valve, out PTC valve works on the principle of vacuum differential between intake and crankcase. Based on this differential, it restricts or allows the crankcase gases to return to the intake. This PCV valve is fully or almost closed at idle and full load, and opens and closes variably in-between, based on (again) the differential of vacuum between intake and crankcase. That is why it has a vacuum line from the tree (next to the throttle body), and of course a hard-plastic line that comes from the crankcase (via the Breather / Oil Separator).

[wjhandy850]

Great to see that you guys are digging into this. I am also going to check my PTC heater, as well. I'm keeping up with this one. Now what is (P) ?

Do the heaters go out on this thing?

[Ozark Lee]

Do the heaters go out on this thing?

Nothing is impossible but the dang things just normally cause problems due to being plugged up with gunk. You can get very aggressive when cleaning it and it won't hurt the heater but aggressive solvents will screw up the rubber on the intake snorkel where the valve mates in. Don't try to clean it while it is in the snorkel tube, go ahead and remove it before cleaning it.

...Lee

[jblackburn]

1/2 a can of carburetor cleaner got mine nice and clean. Make sure you run a paperclip or drill bit or something through the small vacuum port on the side.