Radiator Fan Always On, No Engine Light, No ALDL, No Code 12.....Problem Resolved
09-16-2022, 09:20 PM
#1
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Location: Ontario, Canada
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Car: 1988 Iroc-Z
Engine: 350 TPI L98
Transmission: 700R4 Auto.
Radiator Fan Always On, No Engine Light, No ALDL, No Code 12.....Problem Resolved
Hello to all,
Yesterday I was working on a 1986 5.0L TPI IROC Z.
I ran into a very unusual situation. The symptoms were as follows:
When the key was in the on position there was
- no check engine light illuminated, but sometimes there was a check engine light, randomly
- the primary electric fan was always running
(as if the A and B port were jumped)
-but when you put the jumper into the A and B ports of the ALDL no code 12, its as i there were no jumper
-when the car started it had no check engine light: it ran rough but sometimes it didnt and when you put it into gear and tried to move it would stall.
It turns out the MEMCAL was intermittently not seating properly into the ECM. Which is really strange because it happened randomly out of the blue. The only possibility I can see is that gentlemen that was driving the car was driving with warped bald tires with no wheel weights and the car was vibrating like crazy. the two screw holding the Memcal cover plate were not turning in tight enough to hold the plate on. Pressure from the gasket on the plate had to be putting pressure onto the MEMcal to hold it firmly into the socket in the ECM to stop the issue.WIthout pushing onto the Memcal to hold it in place the issue would continue. To be clear the two levers that press down to lock the Memcal in place were in tact and functioning. Even with another ECM swapped the Memcal had to have pressure applied to prevent this issue from continuing.The chip in the ECM happens to be a Hypertech.
Anyone ever see this unusual issue before????
Yesterday I was working on a 1986 5.0L TPI IROC Z.
I ran into a very unusual situation. The symptoms were as follows:
When the key was in the on position there was
- no check engine light illuminated, but sometimes there was a check engine light, randomly
- the primary electric fan was always running
(as if the A and B port were jumped)
-but when you put the jumper into the A and B ports of the ALDL no code 12, its as i there were no jumper
-when the car started it had no check engine light: it ran rough but sometimes it didnt and when you put it into gear and tried to move it would stall.
It turns out the MEMCAL was intermittently not seating properly into the ECM. Which is really strange because it happened randomly out of the blue. The only possibility I can see is that gentlemen that was driving the car was driving with warped bald tires with no wheel weights and the car was vibrating like crazy. the two screw holding the Memcal cover plate were not turning in tight enough to hold the plate on. Pressure from the gasket on the plate had to be putting pressure onto the MEMcal to hold it firmly into the socket in the ECM to stop the issue.WIthout pushing onto the Memcal to hold it in place the issue would continue. To be clear the two levers that press down to lock the Memcal in place were in tact and functioning. Even with another ECM swapped the Memcal had to have pressure applied to prevent this issue from continuing.The chip in the ECM happens to be a Hypertech.
Anyone ever see this unusual issue before????
Last edited by BlksIrocZ; 09-16-2022 at 09:30 PM.
the Hypertech could have a pcb with dip causing issues Trending Topics
09-20-2022, 01:41 PM
#11
Re: Radiator Fan Always On, No Engine Light, No ALDL, No Code 12.....Problem Resolved
I can but not sure how to do shipping, usps and ups are not going to Canada right now as far as I know. I can possibly try to sell what you need on eBay and see if we can send third party. Send me a pm if you like.
09-20-2022, 08:09 PM
#12
Re: Radiator Fan Always On, No Engine Light, No ALDL, No Code 12.....Problem Resolved
The DIP socket is an Augat/TE piece, 28-pin beryllium-copper with 0.100" spacing (standard item). The old number was 4-278, but since TE/Tyco took them over it might have changed. It fits under the MEMCAL cover, but just barely.
It uses machined (not stamped) contacts with gold plating to resist oxidation, and is only 0.165" high.
https://www.peconnectors.com/sockets-dip-ic-machined/hws2117/
https://www.mouser.com/ProductDetail...9EmpsYgw%3D%3D
It uses machined (not stamped) contacts with gold plating to resist oxidation, and is only 0.165" high.
https://www.peconnectors.com/sockets-dip-ic-machined/hws2117/
https://www.mouser.com/ProductDetail...9EmpsYgw%3D%3D
Last edited by Vader; 09-20-2022 at 08:16 PM.
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