cilinder head temp.sensor
 

Is it possible a failure in the cilinderhead temp.sensor that my 3.2 1986 carrera is not starting when the engine is warm

yes, that can be a cause, but a failing head temp sensor generally affects the engine when it's cold, not hot -- more frequently, this is a symptom of a failing DME Relay. Do you have a spare DME relay and, if so, have you tried swapping it out? (everybody that has a 84-89 Carrera should purchase and carry with them a spare DME relay, as vibration causes their soldier joints to fail, resulting in no-start situations). If you don't have a spare DME relay, worth tapping on it (it's under the driver's seat, behind the DME computer) while trying to start and seeing if that makes any difference.

Could be CHT, Speed or Reference Sensor, DME Relay.

I would take a multimeter and check each one at the plug on the driver side. There are 3 plugs connected on the holder on the intake. Do you have the manual for the specs each should have.

If it is CHT as it is temp related get one of these:

https://www.amazon.com/dp/B07VBQFFG2?psc=1&ref=ppx_yo2ov_dt_b_product_detail s

Cheap CHT remover and installer.

Im leaning toward relay.

http://forums.pelicanparts.com/porsche-911-technical-forum/893047-3-2-wont-start-when-engine-operating-temp.html

http://forums.pelicanparts.com/porsche-911-technical-forum/618346-3-2-hot-start-problem.html

actually the number one failure of CHT is when engine is warm it chokes and stalls out. If this is your issue, jumper it with a paperclip at the connector ( i think its the top white one but someone will chime in if i am incorrect ) . If car starts and runs no problem that is your issue. Every 3.2 should have a paperclip in the tool kit, this trick could get you home in an emergency, remember to remove the paperclip when engine is cold of course.

Its the top white as theiceman says. but do an ohm check on it.

CHT Sensor Resistance from Bentley
*
0C = 4.4 to 6.8 K Ohm
15C to 30C = 1.4 to 3.6 K Ohm
40C = 1.0 to 1.3 K Ohm
80C = 250 to 390 Ohm
100C = 160 to 210 Ohm
130C = 90 Ohm




Characteristic Application
T [°C] R [Ohm]
-40 45,313
-30 26,114
-20 15,462
-10 9,397
0 5,896
10 3,792
20 2,500
30 1,707
40 1,175
50 834
60 596
70 436
80 323
90 243
100 187
110 144
120 113
130 89