'89 SHO with cooling fan issue

[MurseShawn]

I have an '89 MTX with 110,00km and a cooling issue. Cooling fans have not been turning on, leading to overheating. Fan does not turn on with AC turned on either. Coolant and Thermostat seems to be good and coolant is cycling through rad. Placed into test mode by bridge test plug to pull OBD -1 codes. Have 24/25/73 codes, none of which seems related to Cooling fans.

Interestingly the fans come on during the test process! This led me to think it was a faulty engine coolant sensor. Replaced with new sensor. This did not resolve the issue. Any thoughts out there? Is it likely the CCRM?

Help!

 

[zoomlater]

It could be the problem, do you have access to anyone close by that may have spare you can try. Do you have an M code installed

http://www.shosource.com/catalog/product_info.php?cPath=61_46&products_id=42

 

[SHOdded]

Assuming the fan wiring/connector are in good shape. Could be corroded/broken internally. The usual culprit is the CCRM tho.

 

[MurseShawn]

Wiring appears to be good. Oddly fan runs during the OBD test process. It is a correct M code CCRM.

 

[sperold]

It sounds like you know what you are doing, but just a reminder, there is a temp sensor for the gauge and another temp sender for the engine management system.

Make sure you changed the engine management temp sensor.

If the fan runs during the test sequence, that suggests the CCRM and the engine fan are still getting along.

 

[rubydist]

If the fan runs during the test, then you know the ccrm and fan both work. That leaves you with two choices: either the pcm doesn't know that the coolant is getting too hot or the pcm isn't commanding the fans to come on. Note that the issue may not be with the temp sensor or the pcm, but rather in the wiring so that the signal is not getting communicated to the ccrm. Since the fan runs during the test, that tells you that the pcm can successfully communicate to the ccrm to turn the fan on, so I would conclude that the temp sensor, or the wiring relating to the temp sensor are the culprits here.

 

[Dale Leonard]

I have an '89 MTX with 110,00km and a cooling issue. Cooling fans have not been turning on, leading to overheating. Fan does not turn on with AC turned on either. Coolant and Thermostat seems to be good and coolant is cycling through rad. Placed into test mode by bridge test plug to pull OBD -1 codes. Have 24/25/73 codes, none of which seems related to Cooling fans.

Interestingly the fans come on during the test process! This led me to think it was a faulty engine coolant sensor. Replaced with new sensor. This did not resolve the issue. Any thoughts out there? Is it likely the CCRM?

Help!

I have owned several 89 sho's and on two of them I had trouble with the fans after 100,000 miles. I took the fans apart and put new brushes in and it fixed my problem. The brushes were worn and I could not find brushes. I went to an outboard motor shop and bought the correct hardness of brushes and filed them down to fit the slots. I then cut the old connection wires and inserted the wires from the new brushes and soldered then togather. Fans lasted more than another 100,000 miles. Mine would work interdemediatley or not at all. Never looked at sensors.

 

[MurseShawn]

If the fan runs during the test, then you know the ccrm and fan both work. That leaves you with two choices: either the pcm doesn't know that the coolant is getting too hot or the pcm isn't commanding the fans to come on. Note that the issue may not be with the temp sensor or the pcm, but rather in the wiring so that the signal is not getting communicated to the ccrm. Since the fan runs during the test, that tells you that the pcm can successfully communicate to the ccrm to turn the fan on, so I would conclude that the temp sensor, or the wiring relating to the temp sensor are the culprits here.

I assume I could test the voltage at the ECT sensor terminal with a voltmeter. Would you know the voltage I should be seeing?

 

[luigisho]

I have owned several 89 sho's and on two of them I had trouble with the fans after 100,000 miles. I took the fans apart and put new brushes in and it fixed my problem. The brushes were worn and I could not find brushes. I went to an outboard motor shop and bought the correct hardness of brushes and filed them down to fit the slots. I then cut the old connection wires and inserted the wires from the new brushes and soldered then togather. Fans lasted more than another 100,000 miles. Mine would work interdemediatley or not at all. Never looked at sensors.

This is news I can use. Thanks!

 

[rubydist]

I assume I could test the voltage at the ECT sensor terminal with a voltmeter. Would you know the voltage I should be seeing?

I think the ect sensor is a variable resistance device, but I don't know what voltage drop you should expect to see.

If you want to play with a volt/ohm meter, I would measure resistance from the ect back to the pcm.

I think I would start by changing that sensor - they are not that expensive.