hey guys,
This has been going on for a while now, but neither of my boost gauges will work. My cruise control does still work and the vac lines under the battery tray are intact. Does this narrow my problem down to the cabin area/cluster maybe, or is there somewhere else I should also be looking? thanks

 

There are a few threads on this if you search. Basically it's likely a vacuum leak in the lines somewhere. My car has same problem (my gauge stay in middle @ all times and just tweaks slightly over to right on full throttle). I'm going to chase it down when I get the car out of storage in the spring.

 

yea thats what i thought. i checked where i thought the most likely culprits are but ill have to keep looking

 

Let us know what you find.

 

I will. Weather isn't cooperating lately but I may find some time this week

 

Im still curious though, since the cruise control works and the lines under the tray are good does that mean it is the lines inside or should i still trace them back from the engine bay?

 

Someone correct me if I'm wrong here but from what I've read, the line comes out of the driver's side firewall and routes towards the left front headlight, and of course under the battery tray. It then it turns toward the center of the car and goes just behind the hood clasp then back towards the throttle body / vacuum tree. Then I think a line comes from the vacuum tree under the throttle body shield to the turbo control valve right above the turbo.

So there's basically a lot of places it could have gone bad. So I'd start in the engine bay.

Here are a few threads on the problem FWIW...

https://volvoforums.com/forum/volvo-...working-49226/

https://volvoforums.com/forum/volvo-...working-29883/

https://volvoforums.com/forum/volvo-...working-15425/

 

thanks for the clarification!

 

I don't know if this will confuse us even more but here's a diagram I found that shows the gauge hose.

 

i think that will help. it will just take me some time to decipher a bit

 

Problem solved! Starting from the vacuum tree back, where the first piece of vacuum hose is used to connect the two hard lines had come apart(face palm for not catching something so simple sooner). I just cut a longer piece of some of the silicone line I had leftover and used that. Both gauges are working now

 

As an update, I just solved my problem too. I got the car out of winter storage today and first thing I did was check under the battery tray per this thread:

http://volvoforums.com/forum/volvo-850-16/cruise-control-not-working-turbo-boost-guage-not-working-29883/

Sure enough, the off-white plastic hose was cracked in two places, and very brittle in those areas. It literally crumbled into my hand. I cut away what looked to be the bad areas, connected the good ends to a piece of vacuum tubing and presto, the gauge is now working and car feels a lot more lively than it did last year.

That could be my imagination but it makes some sense given the broken line was creating a vacuum leak, and maybe improper signals to the ECU as well. Regardless, I have a turbo gauge now. Thanks RSPI!