boost gauge stopped working
02-28-2015, 03:17 PM
#1
Intermediate
Thread Starter
boost gauge stopped working
I have an 89 944 turbo which I left parked for a couple of months. When I drove it my boost gauge stopped working. I parked the car with the gauge functioning. When the car is in the on position, the gauge goes from vacuum to 1 bar immediately like normal. After the car is started the boost gauge takes almost 2 minutes to go back to vacuum at idle. During driving with normal boost the gauge will slowly creep up but never indicating the correct pressure, moving up during boost just as slowly as it was going down. The car drives normally with normal boost, just as it felt when the gauge was working.
I checked the vacuum tube from the manifold. Looked normal. I took the tube off the KLR unit end and at idle I can feel vacuum. So is it the gauge itself at the instrument panel that is not working? I just had the instrument cluster serviced by Hollywood Speedometer last year and everything was in order until I parked the car for a long time. Where should I start to solve the problem?
Thanks,
David
I checked the vacuum tube from the manifold. Looked normal. I took the tube off the KLR unit end and at idle I can feel vacuum. So is it the gauge itself at the instrument panel that is not working? I just had the instrument cluster serviced by Hollywood Speedometer last year and everything was in order until I parked the car for a long time. Where should I start to solve the problem?
Thanks,
David
02-28-2015, 04:34 PM
#2
Rennlist Member
If there is good vacuum and pressure at the KLR port, then the possibilities would seem to include
1. bad KLR
2. bad wiring to the gauge or cluster, including grounds
3. bad gauge
If you have a multi-meter, you should be able to isolate the problem. This thread should give you the info to track down your problem, if you're handy with a multimeter.
https://rennlist.com/forums/944-turb...e-control.html
You can probe the signal going from the KLR to the gauge in a connector located in the passenger footwell. On later cars, I believe you are looking for the blue wire in an 8-pin black connector (but confirm that by checking to make sure it ohms out to pin 5 on the klr). On earlier cars like mine, the wire is red with a white stripe in a red square 4-pin connector. You can also just bench test the KLR by applying power to it and checking the voltage on pin 5 as you apply vacuum and pressure to its port. On a bench, with nothing but power connected to it, the KLR should show about 2.4 volts on pin 5, and that should go up and down as you apply pressure/vacuum to the port. (If you test it in situ, with the gauge still connected, those voltages should be 1/5th as much across the board.) If klr voltages check out, then you can test the gauge by applying 0 to 5 volts to it through a 4k resistor, as described in the linked thread.
1. bad KLR
2. bad wiring to the gauge or cluster, including grounds
3. bad gauge
If you have a multi-meter, you should be able to isolate the problem. This thread should give you the info to track down your problem, if you're handy with a multimeter.
https://rennlist.com/forums/944-turb...e-control.html
You can probe the signal going from the KLR to the gauge in a connector located in the passenger footwell. On later cars, I believe you are looking for the blue wire in an 8-pin black connector (but confirm that by checking to make sure it ohms out to pin 5 on the klr). On earlier cars like mine, the wire is red with a white stripe in a red square 4-pin connector. You can also just bench test the KLR by applying power to it and checking the voltage on pin 5 as you apply vacuum and pressure to its port. On a bench, with nothing but power connected to it, the KLR should show about 2.4 volts on pin 5, and that should go up and down as you apply pressure/vacuum to the port. (If you test it in situ, with the gauge still connected, those voltages should be 1/5th as much across the board.) If klr voltages check out, then you can test the gauge by applying 0 to 5 volts to it through a 4k resistor, as described in the linked thread.