PDA

View Full Version : temp gauge problem


supturb89
10-01-2010, 12:12 PM
Short story long
96 205 with the 350 TBI

My temp gauge since purchasing the boat is always pegged. With the key off it always pegs to the right. When you turn the key to the ON position the needle moves ever so slightly more to the right. When running the boat it never moves from this position. The PO told me the gauge didn't work and that it was the sending unit. I have replaced the sending unit and the problem still persists. Rmoving the wire from the sending unit causes no change, which leads me to believe it could be a ground issue? I am electrically stupid so that also adds to the problem. All connections on the back of the gauge seem to be tight. I have checked the connection for the wiring harness behind the gauges and it seems to be nice and tight with no corrosion. Is it possible the gauge could be wired incorrectly? On the back there are two purple wires wired together on a post. A tan wire by itself on a post and the black ground. There is also a blue wire which I assume is for the gauge illumination? What should be my next steps, keeping in mind that you will have to explain it like I'm three years old if it has anything to do with an multimeter, which I do have. Another issue that makes this more difficult is the fact that the main wiring harness coming in behind the gauges is so short that I am unable to pull the gauges out far enough to see or work on anything behind the temp gauge.

ahhudgins
10-01-2010, 12:50 PM
If no one has a definite answer, I should have one this weekend. I'm bringing my 95 Maristar home from the lake and I am checking the wiring for my temperature gauge and ECM. I do know that the brown wire is from the sending unit. If the brown wire is disconnected (open circuit) my gauge stays on COLD. If the brown wire is shorted to the block (ground) my gauge goes to max HOT. I also have a sending unit on the thermostat housing with a brown and black wire that is for the "Engine over temp" light on the dash.

My gauge is working fine, I'm just trying to figure out how the gauge and ECM are working off the same sensor. Schematic for the ECM shows the sensor only wired to the ECM. I will get some pictures and check back if you haven't resolved your issue.

supturb89
10-01-2010, 01:24 PM
If no one has a definite answer, I should have one this weekend. I'm bringing my 95 Maristar home from the lake and I am checking the wiring for my temperature gauge and ECM. I do know that the brown wire is from the sending unit. If the brown wire is disconnected (open circuit) my gauge stays on COLD. If the brown wire is shorted to the block (ground) my gauge goes to max HOT. I also have a sending unit on the thermostat housing with a brown and black wire that is for the "Engine over temp" light on the dash.

My gauge is working fine, I'm just trying to figure out how the gauge and ECM are working off the same sensor. Schematic for the ECM shows the sensor only wired to the ECM. I will get some pictures and check back if you haven't resolved your issue.

Would very much appreciate your feedback. Thank you.

supturb89
10-01-2010, 08:42 PM
Removed the wire from the sending unit and grounded it to the block and the gauge then goes way past the 240 degree mark. At this point I think it may be the gauge itself?

BallBushing
10-02-2010, 07:57 AM
I have a 99 Maristar 210 VRS. After being serviced for a starting problem, the gauge stays pegged at max, also will not illuminate when the navigation lights are on (and all other gauges are lit). Also will not move when the battery is disconnected. Planning to pull the dash & clean all contacts. Could it be a bad sending unit?

ahhudgins
10-03-2010, 02:42 PM
Sounds like your gauge is bad and here are a few simple checks to make:
This is with my engine cold...about 75 degrees.
1. Set your meter to DC volts.
2. Connect your negative lead (black one) to the post of the temperature gauge with the
black wire. This is ground.
3. Turn your ignition key to the first click (ON).
4. You should get 12V DC to the purple wire. This comes from your ignition circuit.
5. With a cold engine, you should have around 9V on the brown wire. This comes from the
termperature sending unit. If this checks good and your gauge is showing over 75
degrees, your gauge is bad.
6. Turn the ignition key off. Disconnect the brown wire at the temperature gauge.
7. Turn the key to the first click again. Gauge should be showning cold.
If it doesn't, your gauge is bad. Take a screw driver and short the ground post to the
post that the brown wire came off of. This should cause the gauge to peg to the hot
position.
8. With the key off and the brown wire still disconnected, set your meter to OHMS.
Put one lead to the black post (ground) and the other lead to the brown wire. Should
read around 1.3K (1300 ohms). This is checking the sending unit resistance.
This resistance will decrease as it gets hotter.
9. The blue wire is 12V for the bulb.

supturb89
10-03-2010, 10:29 PM
Sounds like your gauge is bad and here are a few simple checks to make:
This is with my engine cold...about 75 degrees.
1. Set your meter to DC volts.
2. Connect your negative lead (black one) to the post of the temperature gauge with the
black wire. This is ground.
3. Turn your ignition key to the first click (ON).
4. You should get 12V DC to the purple wire. This comes from your ignition circuit.
5. With a cold engine, you should have around 9V on the brown wire. This comes from the
termperature sending unit. If this checks good and your gauge is showing over 75
degrees, your gauge is bad.
6. Turn the ignition key off. Disconnect the brown wire at the temperature gauge.
7. Turn the key to the first click again. Gauge should be showning cold.
If it doesn't, your gauge is bad. Take a screw driver and short the ground post to the
post that the brown wire came off of. This should cause the gauge to peg to the hot
position.
8. With the key off and the brown wire still disconnected, set your meter to OHMS.
Put one lead to the black post (ground) and the other lead to the brown wire. Should
read around 1.3K (1300 ohms). This is checking the sending unit resistance.
This resistance will decrease as it gets hotter.
9. The blue wire is 12V for the bulb.

ahhudgins,
Thank you for taking the time to write this up and supply a diagram. Those directions were spot on what I needed to know. Steps 6 and 7 are where my gauge still shows hot, so I have concluded it is the gauge and have ordered a replacement. Thanks again!

ahhudgins
10-04-2010, 08:21 AM
Glad I could help you out. I just happened to be working on an issue with the sending unit in my 95 Maristar. I have the wiring diagram for the ECM from Indmar and Pleasure Craft which are almost identical but the wire colors don't match my boat. :confused:

supturb89
10-04-2010, 03:11 PM
I may have the same diagram from Indmar as you and I too noticed the colors don't match. Here it is just in case it may help you out???

ahhudgins
10-04-2010, 05:48 PM
I may have the same diagram from Indmar as you and I too noticed the colors don't match. Here it is just in case it may help you out???

Thanks, but that's the same one I have.
I may have to drive the 2 hour round trip to the dealer to answer my question. There was a scan tool on Ebay last week but I didn't bid on it because the owner had no way to test it. It went for about $230 and I'm not spending that kind of money on chance.

wgtruemper
06-21-2011, 10:20 AM
I have a similar issue in a '95 PS 190 with the 275 TBI. Beginning last summer, possibly right after my VR went out, I began getting little or no temp reading. I say this because a warm engine looks like it might read 2 or 3 needle widths warmer (about 121F on my gauge) than the gauge reads with the key off. I did the 140F to 160 Tstat switch last year. I replaced the upper temp sender, which now appears to me to be the engine warning "over temp" sender. I warmed up the boat last night and had the "engine over temp" light on almost immediately, even though I know it wasn't. Everything was fine, I have clear hoses on the tstat to exhaust side and could see water flow and nothing got that hot.
I went through ahhudgins' 9 steps above (thank you!) and based on that I'd say that my dash gauge is fine. So now I am thinking that I need to replace the lower temp sender and also need to put back my original upper temp sender. Any other ideas?

wgtruemper
06-28-2011, 12:34 AM
I am still fighting this issue. I have replaced both the sender and the gauge now and I still show 120F on a warm engine. Help!!

ahhudgins
07-22-2011, 05:45 PM
I am still fighting this issue. I have replaced both the sender and the gauge now and I still show 120F on a warm engine. Help!!


Did you get it resolved yet? Make sure you are testing the correct sensors first. The sensor with the solid brown wire is for gauge. Open the wire and your gauge should go to max cold. Short the wire to a good ground and your gauge should go to max hot. If this doesn't happen you may have a wiring issue (if you replaced the gauge).

The sending unit for the "over temp" light has the brown/black wire. Wire open the light is off, wire shorted to ground it is on.