Hypertech Thermo Master chip question
Thread Starter
Racer
Joined: Aug 2014
Posts: 478
Likes: 66
From: Elizabethtown, NC
Hypertech Thermo Master chip question
I am trying to find out what temp the Hypertech Thermo Master chip turns the main cooling fan on and off for a 1985 C4. I did many search's and found the on is 176* but not the off temp. Anybody know what the off temp is. I know I will get beat up for this, but that's ok. Thank you
Le Mans Master
Joined: Sep 2013
Posts: 6,192
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From: near the thumb in the mitten
Fans come on with AC on and about 225*. When car is traveling over about 40 mph the fans are ineffective. If you have a 180* thermostat does engine stay at 180 on the expressway? If not chip won't help.
Team Owner
Joined: Oct 2004
Posts: 81,241
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From: altered state
St. Jude Donor '05
wongs performance .com think hes still a member here
I used that chip along with a 160 thought it was worth it for that alone...wasnt any faster or slower but hate cars that run warm
I used that chip along with a 160 thought it was worth it for that alone...wasnt any faster or slower but hate cars that run warm
Thread Starter
Racer
Joined: Aug 2014
Posts: 478
Likes: 66
From: Elizabethtown, NC
Thank you all for responding. I bought a 1985 C4 Z51 recently and the main fan would come on at 176* and run all the time at 190* without turning off. I ended up finding it has a Hypertech thermo master chip installed with a 190* thermostat. I know it requires a 160* stat but living here in the north east with the cold weather I would rather run a warmer stat for better heat. I presently have a 160, 170 and a 180 stat and was wondering if I could get away with a 170 with that chip and thats why I was asking about the fan turn off degree. I am guessing not about the 170* so at this point I am trying to figure out my options.
Team Owner
Joined: Aug 2004
Posts: 21,543
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From: Park City Utah
I would want something like a 20* spread between my Stat rating and the fan-on setting....less than that and I feel that the fans will be running too much/more than necessary. Remember that the stat rating is when it starts to open. It won't be fully open until it's ~7-10* above it's rating, or so.
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Pro
Joined: Aug 2020
Posts: 647
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From: Liliha Bakery stuffing my face with coco puffs!
Ok, going to need some help here. Took the vette to a vette specialty shop for other issues. Mechanic noticed the fans were operating at all times (key on). here is thier report/invoice "inspect cooling fan relay and found the wiring appears to be correct but the relay is still receiving the signal that makes it engage the cooling fan. After some research we found that the ECM has an aftermarket E-prom chip and that, in combination with a possibly bad ECM, could be causing the ECM to be shorted to ground in the circuit for the cooling fan running continuously when the ignition key is on.
Replaced the ECM and Prom chip and retested the cooling fan system, works as it should at this time, the fan comes on at 175 degrees and goes off at 166.
Hypertech Chip-s #11542 $206.00
ECM-s # 77-6870 $158.00
Labor $245.00"
Sorry for the long details but wanted you to know the full story. Whats wrong with this picture?
Replaced the ECM and Prom chip and retested the cooling fan system, works as it should at this time, the fan comes on at 175 degrees and goes off at 166.
Hypertech Chip-s #11542 $206.00
ECM-s # 77-6870 $158.00
Labor $245.00"
Sorry for the long details but wanted you to know the full story. Whats wrong with this picture?
Read the whole story here: https://www.corvetteforum.com/forums...lent-temp.html
Melting Slicks
Joined: Aug 2003
Posts: 3,401
Likes: 397
From: Lakeville MI
Get yourself a couple of 24-pin 2732 eproms, a compatible programmer, u/v eraser and you can use whatever fan on/off temperatures and thermostat that you desire.
86-89 factory bins typically have a 6° F delta between the fan on and fan off temperature. Note: there is a 15 second delay after the coolant temperature falls below the fan off threshold before the fan will be switched off.
Correction/update: 1985 $1F bins have a hysteresis of 3° C (or 5.4 °F) between fan on and fan off, but no specific fan off temperature setting unlike the later 86-89 bins. Fan off temperature is calculated from Fan on temperature - hysteresis.
I suspect that the hypertech is programmed for 176° F on and 170.6 ° F off considering the standard 3° C (5.4° F) hysteresis setting. I would be surprised if hypertech bothered to change the hysteresis value.
Simplest solution is to run the 160° F stat and just live with the lower coolant temps during the winter. The fan will still run most of the time anyway, except during the winter months. The 170° stat may be a better compromise, but the fan will likely run continuously once activated even during the winter months.
86-89 factory bins typically have a 6° F delta between the fan on and fan off temperature. Note: there is a 15 second delay after the coolant temperature falls below the fan off threshold before the fan will be switched off.
Correction/update: 1985 $1F bins have a hysteresis of 3° C (or 5.4 °F) between fan on and fan off, but no specific fan off temperature setting unlike the later 86-89 bins. Fan off temperature is calculated from Fan on temperature - hysteresis.
I suspect that the hypertech is programmed for 176° F on and 170.6 ° F off considering the standard 3° C (5.4° F) hysteresis setting. I would be surprised if hypertech bothered to change the hysteresis value.
Simplest solution is to run the 160° F stat and just live with the lower coolant temps during the winter. The fan will still run most of the time anyway, except during the winter months. The 170° stat may be a better compromise, but the fan will likely run continuously once activated even during the winter months.
Last edited by tequilaboy; Jan 12, 2021 at 11:33 AM.
Pro
Joined: Aug 2020
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From: Liliha Bakery stuffing my face with coco puffs!
Do you have a link to an xdf that identifies the off temp? I was only able to find the scalar for on temp when poking around TP.
Added: Duh! Sorry I didn't read your reply and based my question on poking around a bin and xdf.
Added: Duh! Sorry I didn't read your reply and based my question on poking around a bin and xdf.
Last edited by stew86MCSS396; Jan 11, 2021 at 06:18 PM.
Thread Starter
Racer
Joined: Aug 2014
Posts: 478
Likes: 66
From: Elizabethtown, NC
Thank you everybody for very good advise and information. So at this point and time I going to install the 160* stat and see if my heat will suffice for New York winter and if not I know my other options now.
Thread Starter
Racer
Joined: Aug 2014
Posts: 478
Likes: 66
From: Elizabethtown, NC
