how do you recognize a non GM prom
Thread Starter
Racer
Joined: Mar 2001
Posts: 269
Likes: 1
From: woodstock, Ga
how do you recognize a non GM prom
Just picked up an 85 4/3 the cooling fan kicks on at 178 deg. with a 195 thermostat, the prom carrier has "RN" embossed on it and I'm wondering if the prom was changed?? also smells rich? any help is appreciated.
Melting Slicks
Joined: Apr 2001
Posts: 2,105
Likes: 220
From: Ca.
Re: how do you recognize a non GM prom (frank moran)
If it's turning on the fan at that temp, then it's not stock gm programming-as to who did it??? Seems like all the tuners have different labels-then there's the "home brewed" too! Have you scanned it to see where the blms are?
Drifting
Joined: Mar 2001
Posts: 1,636
Likes: 3
From: Lafayette IN
Re: how do you recognize a non GM prom (frank moran)
2 things.
1) On the 85, the cooling fan could be controlled by either the ECM or the temp switch in the passenger side head. On later years, the temp switch was changed to the drivers side head. Disconnect that connector and see if your fan still turns on at 178-180 deg F. This will rule out possibly only having a low-temp fan switch. Drivers side head in 85 controls the dash gauge.
2) I think even aftermarket chips on 85 will have that embossing on the carrier. However, I have never seen an aftermarket chip with a small square of foil over the center of the chip, and I have never seen a factory untouched chip with anything but foil over the UV erasing window. If there is no foil over the center of the chip (but under the carrier), it is likely your chip is aftermarket.
1) On the 85, the cooling fan could be controlled by either the ECM or the temp switch in the passenger side head. On later years, the temp switch was changed to the drivers side head. Disconnect that connector and see if your fan still turns on at 178-180 deg F. This will rule out possibly only having a low-temp fan switch. Drivers side head in 85 controls the dash gauge.
2) I think even aftermarket chips on 85 will have that embossing on the carrier. However, I have never seen an aftermarket chip with a small square of foil over the center of the chip, and I have never seen a factory untouched chip with anything but foil over the UV erasing window. If there is no foil over the center of the chip (but under the carrier), it is likely your chip is aftermarket.
Thread Starter
Racer
Joined: Mar 2001
Posts: 269
Likes: 1
From: woodstock, Ga
Re: how do you recognize a non GM prom (frank moran)
it does not appear to have any type of foil on it, I will check much closer though. The fan switch is also new and a factory piece. I can only assume at this point that the prom has been changed, but I need to check closer...any help is appreciated.
Would have replied earlier but I was out of town....
Would have replied earlier but I was out of town....
Thread Starter
Racer
Joined: Mar 2001
Posts: 269
Likes: 1
From: woodstock, Ga
Re: how do you recognize a non GM prom (frank moran)
all, the prom has foil or paper under the carrier and some numbers and letters, cant decern if it is factory. it appears to have been in place some time, i suspect it is after market. I'm ordering a new one, ps yes the temp switch is stock w/ a 195 thermostat., fan still kiks on at 172 ish
Drifting
Joined: Mar 1999
Posts: 1,931
Likes: 1
From: Norcross GA
Re: how do you recognize a non GM prom (frank moran)
If the foil is in place, there is a very good chance it is stock, as you have to remove the foil to erase the PROM. (I have never found a tuner who replaces foil patches.) The lettering on the foil is the BCC code info. (4 Letters, 4 numbers.)
Thread Starter
Racer
Joined: Mar 2001
Posts: 269
Likes: 1
From: woodstock, Ga
Re: how do you recognize a non GM prom (ZylaRace)
what else can kick the fan on early? would the prom not just be a repalcement, i did not think many after market people would reprogram the old prom, just buy another and plug it in???No?
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Racer
Joined: Sep 2002
Posts: 270
Likes: 1
From: Torrance California
Re: how do you recognize a non GM prom (frank moran)
Frank moran,
If or when you replace your chip with the factory one, could u please post where u purchased it, and how much.
I also have an 85, and I need to change my after-market chip with a factory one. Do to smog test coming up.
Would any one have any idea if this is a part # for an 85 chip. This # is on a silver sticker on the chip #1616AZFT9157
If or when you replace your chip with the factory one, could u please post where u purchased it, and how much.
I also have an 85, and I need to change my after-market chip with a factory one. Do to smog test coming up.
Would any one have any idea if this is a part # for an 85 chip. This # is on a silver sticker on the chip #1616AZFT9157
Drifting
Joined: Mar 1999
Posts: 1,931
Likes: 1
From: Norcross GA
Re: how do you recognize a non GM prom (1SLO POK)
Slow Poke,... take those #'s to your dealer. Order a MemCal pak. It should be upwards of $33. (Email Jeff Kopp) This way you still have you custom burn to plug in later.
Frank,
Some tuners use an adapter to reprog the chip while in the MemCal. Some put the PROM on a socket. I do this. It is not easy, but it works best for what I do. Others replace the PROM w/ the FLASH, then use the adapter to reprogram it every time.
The 85 is a different kind of beast, but it should still take a general approach to the fans,....... coolant warm enough = fan On, ECM failed = fan On, AC On = Fan On
If you have 2 radiator fans,.... one is usually tied to the cyl coolant sensor, the other is controlled by the ECM. That is kinda the nutshell approach, I do recall there were difference, but I don't recall the details.
If you can afford down time, send me the MemCal and I may be able to read it for you.
Frank,
Some tuners use an adapter to reprog the chip while in the MemCal. Some put the PROM on a socket. I do this. It is not easy, but it works best for what I do. Others replace the PROM w/ the FLASH, then use the adapter to reprogram it every time.
The 85 is a different kind of beast, but it should still take a general approach to the fans,....... coolant warm enough = fan On, ECM failed = fan On, AC On = Fan On
If you have 2 radiator fans,.... one is usually tied to the cyl coolant sensor, the other is controlled by the ECM. That is kinda the nutshell approach, I do recall there were difference, but I don't recall the details.
If you can afford down time, send me the MemCal and I may be able to read it for you.
Thread Starter
Racer
Joined: Mar 2001
Posts: 269
Likes: 1
From: woodstock, Ga
Re: how do you recognize a non GM prom (ZylaRace)
yes, I did order a prom today from jeff k in KC for about $36., the aux cooling fan looks like its controlled by the therm switch in the right head, and the primary one by the ecm, at least I hope so since I ordered a prom. I'll keep you posted, I wont get the prom for about 10 days. The down time is not aa issue, I have plenty to do on this one. are you saying you program the cal pak and not the prom? I thought just the prom was what needed to be reprogrammed, the cal pak is a back up limp home feature....thanks for your help, I'm pretty sure what I have now is after market..been in there awhile..
Drifting
Joined: Mar 1999
Posts: 1,931
Likes: 1
From: Norcross GA
Re: how do you recognize a non GM prom (frank moran)
Yes, all you really need is to swap the PROM, but most people find it easier to swap the MemCal. If you take the blue cover off your MemCal, you may find the PROM to be socketed. Most are soldered, hence it is easier to swap the MemCal.
The early C4's are as you describe, 1 on the ECM, 1 on the cyl head therm switch. As long as the fan does not come on when you turn the key ON, (cold engine), the fan is probably doing as it is programmed to do. For a tuner, changing the fan On temp is rather easy to do.
The early C4's are as you describe, 1 on the ECM, 1 on the cyl head therm switch. As long as the fan does not come on when you turn the key ON, (cold engine), the fan is probably doing as it is programmed to do. For a tuner, changing the fan On temp is rather easy to do.
Thread Starter
Racer
Joined: Mar 2001
Posts: 269
Likes: 1
From: woodstock, Ga
Re: how do you recognize a non GM prom (ZylaRace)
zyla, I just put the new factory prom in and the fan kicks on and off as designed. On about 224 off about 200.... The prom was the problem. Ths new carrier aslo had the RN embossed in it, someone must have flashed the one I removed.
