Hi, my coolant gauge, and boost gauge never worked on my 88' t2. The fuel works and oil pressure kind of works. Any idea how to get the coolant gauge to work for now? Car is on haltech RE, and I will be installing aftermarket gauges soon, but would like to have the coolant gauge functioning.

 

Regarding your water temperature gauge not working, I would first check the sending unit and/or wire connecting to the sender which is located under the oil filter pedestal. Here's a link with photo of the sensor: https://www.atkinsrotary.com/81-88-R...9-18-510A.html

Regarding your boost gauge not working, I would first check the boost sensor and vacuum hose. The boost sensor is a little black box located on the passenger side inner fender near the strut tower. Here's a link with photo of the sensor: https://www.atkinsrotary.com/87-88-T...18-18-211.html

 

the coolant temp sensor wire, and the boost gauge wire both were in the original engine harness.
the coolant temp wire goes right from the gauge to the sender, its simple.
the boost sensor is teed into the factory boost sensor wire, so it wants a 2 bar MAP sensor 0-5v signal

 

i don't recall if the haltech RE has a boost signal auxiliary output, unlikely though since that is a rather antiquated ECU now. the coolant sensor wire often gets taken out of the loop by lazy turds who can't rerun a new wire from the sensor to the gauge, they rather just omit it when they build a new harness. it's just a single wire that can be tied to the jumper harness near the left front strut tower IIRC.

you can always wire up a factory pressure sensor just to feed the gauge, however it needs a 5v reference, ground and a signal wire to the gauge, more than most care to bother with.

 

ill look into it. I havent touched the car at all this week, but last I checked, there was a wire coming from the sensor into the harness. This car has good bones but some jank work done to it so i wouldnt be suprised.

 

it's been many many years since i fiddled with an FC harness so going off memory and it's hazy now. i'f you're having trouble tracing the harness i can open up my wiring schematics to try and help remember exactly where it goes in the car.

 

the yellow/white coolant temp sensor wire runs through the main engine harness up to where the stock ECU should have been and had a small pigtail to meet FEM-01 just above the right kick panel in the passenger foot well. FEM-01 is a 22-1 pin connector(-1 for the locking tab location top center).

conversely you can simply rule out the wiring by temporarily grounding the terminal where it connects to the temp sensor, the gauge should peg beyond hot when turning the key on momentarily(do not leave it on for more than a few seconds) if the wiring is ok and tell you the sensor is bad. the sensors rarely fail though(unless it is an aftermarket one, no guarantees there).

 

thats smart. I ended up replacing the sensor earlier. Didnt seem to help. Will try grounding the wire tomorrow to confirm that its a dash issue. Im not too familiar with these cars but the harness may be aftermarket, Looks too clean/new.

 

good advice. grounding it makes it slowly rise to the top. however the old oem sensor and the new replacement both only rise the slightest bit, .5 or so cm when the car is warmed up

 

How do you verify the car is fully warm? I just went through something similar. The bottom? hose of the radiator should be around 180? + deg F. Other threads recommend using a remote temp reader. Maybe the thermostat is in backwards or stuck open?

When you grounded the gauge in the cluster, did you ground it to the engine or other? Your engine ground could be insufficient. If you can verify that you don't have excessive voltage on your grounds, it might be helpful. Just a Volt meter from one end to the other. I think anything higher than .02? volts would be problematic for ECU sensors grounded to the engine but probably not so much other stuff. I think that this is called... a ground offset test.

This is a weird one... anyone else have ideas?

Also, if you didn't know like I did,four days ago, the FC stock needle only reaches 1/4 of the way up when fully warm, on an s4 anyway.

 

I don't know what centimeters means on the gauge readout, the FC doesn't even get to the half way point at normal operating temperature, if it ever does get to half and continue past it you need to shut off the engine immediately. This is especially true for the S5 1989-1991 models which have a buffered dummy type coolant gauge(anything over half means your engine is already overheating).