How To Read Ac Delco Radio Service Reference Number
This guide describes some of the diverse radio receivers used in 60'due south, 70's, and 80's Chevrolet cars and pick-upwardly trucks. GM offered numerous radio, stereo, and tape histrion options over the years so it is nearly incommunicable to compile an all inclusive listing. Shown here is simply a list of some of the more than common shaft spacing and dash opening sizes along with some mutual electric connectors plant throughout this twelvemonth range. Radios pictured here are for illustration purposes only, this is not a list of radios for sale.
Shaft Spacing, Eye Opening Sizes, and Case Photos
6one⁄four" shaft spacing with 41⁄2" ten oneix⁄16" eye opening
Some vehicles using this size radio include:
- 1964 - 1966 Chevrolet trucks
- 1963 - 1964 Chevrolet full-size cars
Annotation: Both auto and truck applications feature a recessed area bandage into the face up plate around the RH tuning knob shaft. This surface area is unused on truck radios and has a fairly long mounting collar around the RH shaft that extends all the fashion out to the nuance (where information technology is secured with a nut). Machine radios make use of the recessed area to accommodate an optional forepart/rear fader command used for a rear speaker. Therefore, the machine radios have a shorter mounting neckband around the RH shaft. The cutout in the car dash opening has a larger pigsty on the RH side for the special cupped mounting washer used in conjunction with the shorter/recessed collar.
There are likewise some diffences in the bottom/rear mounting support on the machine vs. truck radios in this year range. The car radio has provisions for a support subclass to attach to the bottom comprehend plate. While the truck radio uses a mounting bracket fastened to the rear of the instance.
6one⁄4" shaft spacing with 41⁄2" x 13⁄4" (or 1xiii⁄16") center opening
Some vehicles using this size radio include:
- 1969 - 1976 Chevrolet Camaro
- 1969 - 1976 Chevrolet Nova
- 1969 - 1972 Chevrolet Impala/Caprice
- 1969 - 1972 Chevrolet Chevelle/Malibu/ElCamino
- 1970 - 1972 Monte Carlo
Note 1: The center portion of the faceplates on these radios are slightly larger than the dash opening. That is because they are designed to accept the faceplate fitting up against the back of the dash (instead of fitting through the heart opening).
Annotation 2: The coloring of the lens changed from green to bluish former around 1971 for most models.
Notation three: The 1969 versions of these radios used a different electrical connector than the 1970+ ones. Run across the Electrical Connections and Common Wire Color Codes section for details on the wiring changes.
61⁄4" shaft spacing with 4i⁄2" x 2i⁄4" heart opening
Some vehicles using this size radio include:
- 1967 - 1972 Chevrolet/GMC C/Yard series trucks
- 1969 - 1972 Chevrolet K5 Blazer and 1970 - 1972 GMC K5 Jimmy
- 1971 - 1980's Chevrolet/GMC G series vans
v3⁄iv" shaft spacing with 41⁄4" ten ii" center opening
This radio size was introduced in 1973 and by the late 70's to early 80's it had become the GM corporate standard for well-nigh trucks and rear wheel drive cars. The GM service & repair literature ofttimes refers to these as Delco 2700 series units.
Some vehicles using this size radio include:
- 1973 - 1986 Chevrolet & GMC C/K series trucks, Suburbans, and K5 Blazer/Jimmy
- 1987 - 1988 Chevrolet & GMC R/V series trucks, Suburbans and Blazer/Jimmy
- 1977 - 1979 Chevrolet Nova & GM X-body cars
- 1977 - 1981 Chevrolet Camaro & Firebird
- 1977 - 1982 Chevrolet Corvette
- Many 1973 to early on 80's Chevrolet / GM full & mid-size cars
Note: This listing is grouping these radios according to the knob spacing and middle hole dimensions only and does non accept into account the wiring change that took place in 1978. Run across the Electrical Connections and Mutual Wire Color Codes department for details on the wiring changes.
Notation: The center portion of the faceplates on many of these radios is taller (and a piddling wider) than the actual nuance opening. That is because they are designed to have the faceplate fitting up against the back of the dash (instead of fitting through the centre opening).
Electrical Connections and Common Wire Color Codes
| Socket on Back of Radio | Corresponding Connector(s) | Connector Pin-out Diagram |
|---|---|---|
 |  |  |
| The 3 last radio socket shown in a higher place is used on many 1963 & newer Chevy cars and trucks with mono AM or AM/FM radios. I believe it continued to be used in cars until 1968 and pickup trucks until 1972, possibly beyond that in some applications. The 3 terminal plug that fits these radios is part of the speaker harness and uses Packard 56 series female terminals on the speaker wires. The power wire connection uses a special extension or "piggyback" terminal with a female cease that plugs into the radio and a male person stop that accepts a unmarried-terminal power wire connector from the vehicle. On most cars, the power wire is role of the nuance harness. On most pickup trucks, the ability wire is a separate wire that merely plugs into the fuse box and runs over to the radio. On cars equipped with a rear speaker, a second sub-harness (with matching iii-terminal plugs) is jumpered in betwixt the radio and front end speaker harness. This sub-harness connects to a fader control (that slides over the RH tuner shaft) and is used to split up the radio'south single speaker output between the front and rear speakers. Wire color codes for this style of radio connector varied, merely the most common are:
| ||
| 1969 radios apply a connector that is unique to this twelvemonth. Distressing, no photos or diagrams for this connector yet. | ||
| Socket on Back of Radio | Corresponding Connector(south) | Connector Pivot-out Diagram |
 |  |  |
| The half dozen cavity radio socket & plug shown above is used on 1970 - 1976 Novas and Camaros & 1970 - 1972 Chevelles with AM or AM/FM mono radios. The mating plug that fits into the dorsum of the radio is part of a speaker/jumper harness. It uses Pack-Con female terminals. The jumper harness as well includes a 3-terminal power/light/ground connector that uses Packard 56 series terminals and plugs into a mating connector that is part of the car'south dash harness. Annotation that the example pictured above is from a radio designed to operate a unmarried speaker. So it has an empty crenel in location "B" instead of a rear speaker + concluding. Wire colors for the speakers sometimes vary, but for the most part they tend to exist standardized to:
| ||
| Socket on Back of Radio | Corresponding Connector(s) | Connector Pin-out Diagram |
 |  |  |
| The 10 cavity radio socket shown above is used on many Chevy cars starting in 1971. Exceptions include 71 & 72 Chevelles, and 71 through 76 Novas & Camaros which used the 6 or 9 terminal connectors shown above. Novas & Camaros used this 10 terminal style for 1977 but. Information technology was also used in 1973 - 1977 GM pickup trucks, Blazers/Jimmys, and Suburbans. The socket is divided into iii sections, each of which accepts a plug that uses female Pack-Con terminals. The three-terminal power/low-cal/ground plug is function of the nether-dash harness and the wire color coding on this is unremarkably:
The 3-concluding and four-terminal speaker plugs are office of the speaker harness(es) and the wire color coding depends on the particular radio and awarding. Not all terminals are present for single speaker and front/rear mono applications. The speaker harnesses on some 2-speaker stereo setups ran ane speaker off the front, the other off the rear, and used five pes sections of 2Ω-per-human foot resistance wire (10Ω total) to take the place of the other 2 speakers. Some 1976 & 77 stereo radios utilize a very similar looking eleven crenel connector (not shown). Those take a 4-terminal (instead of iii-terminal) connector for the rear speakers; giving each rear speaker it's own basis/return wire. Some of these radios featured a digital tuner and clock brandish. These will have an additional ii-wire pigtail/socket on the dorsum with orange and brownish wires that are continued as shown for the following fashion. | ||
| Socket on Back of Radio | Respective Connector (s) | Connector Pin-out Diagram |
 |  |  |
| The 12 terminal socket shown above is used on nearly all GM radios/stereos/tape players from 1978 up into the early 1990'south (certain models). The socket is divided into three 4 terminal sections (power, front speakers, and rear speakers). Radios with digital tuners / clocks have an additional 2 terminal connector. The wire colors on these connectors seem to exist standardized to:
Not all radios with this fashion of connector make use of all the available connectors or terminals. For example, single speaker mono radios just have low-cal/nighttime dark-green speaker wires going to terminals A and C on the white connector and the blue rear speaker connector isn't fifty-fifty used at all. The black 2-terminal connector used on digital radios uses Pack-Con terminals and is ordinarily on information technology'due south ain sub harness. The orange wire usually plugs into the "BAT" tap point on the fuse box. And the brown wire normally plugs into the parking light circuit on the headlight switch. | ||
Speaker Information
Polarity:
Speaker terminals are often (but not always) marked with + and - symbols to denote the polarity. Connecting them backwards won't exercise any harm merely it will cause the speaker cone to move in the opposite management. That tin cause sound cancellation issues if 1 speaker is wired correctly and the other is wired with reverse polarity.
On speakers where the terminals are not clearly marked, a quick cheque can be washed using a 1.5V battery. Disconnect the speaker to be tested and temporarily claw it up to the battery while watching the speaker's cone. If the cone moves out and so the speaker'south + terminal is the ane hooked to the + side of the bombardment. If the cone moves in and then the speaker's - terminal is hooked to the + side of the battery.
Grounding:
Virtually threescore'south and many early on 70's Delco radios use grounded speaker systems. With these grounded speaker systems, the negative (-) speaker terminals are continued to the vehicle's metallic body. And any negative speaker connections on the radio plug are internally continued to ground (the radio'south metal case). This allows rear speakers in some motorcar applications to only take a single wire running from the radio back to the speaker (and a short basis wire from the negative speaker final to the car body).
Delco radios from the mid/late 70's and newer have ungrounded speaker systems and will be damaged if any of the speaker wires are connected to ground. When in incertitude, run all of the speaker wires back to the appropriate terminals on the radio.
Impedance:
Most transistorized Delco radios (as shown on this page) take the output transistor(due south) biased to work with 8Ω to 10Ω speakers. I take read (but non confirmed) that the 1979 & newer ETR (electronically tuned receiver) Delco steros have amplifier circuits capable of driving 4Ω speakers.
Here is a skillful source for 8 - 10Ω speakers in the correct sizes to fit near older vehicles: Southward & Grand Electro-Tech Archetype Automobile Speakers.
Stereo Separation:
Stereo channels are typically separated left and right. However, some vehicles have one stereo channel feeding the front speaker and the other channel feeding the rear speaker.
Other External Components
Fader Controls:
About applications with rear speakers use a fader control to split and adjust the output between the front end & rear speakers. These fader controls are a specially constructed rheostat that slides over the radio'due south tuning shaft. The fader control assembly also includes a knob (that is styled to match the awarding) and wires that plug into a speaker wiring sub-harness.
One-time effectually 1972, Delco started edifice radios with built-in fader controls. The born control eliminated the demand for extra wiring and provided rear speaker output connections directly on the radio. The letter Chiliad nigh the end of the radio's Service Model Number designates a model with an integral fader control. I believe dealer installed rear speakers continued to use the external fader controls.
Convector Assemblies:
All radios covered on this page have the output transistor(s) mounted on a heatsink. Most are an integral part of the radio assembly. Notwithstanding, some applications (like early on AM/FM receivers) did non have enough room inside the radio case so these components were mounted externally. These external heatsink / transistor assemblies were refered to as "convector assemblies" in the Delco radio literature.
A radio that uses one of these external convector assemblies will not role correctly without one. Still, a missing convector assembly commonly isn't a major trouble. A functional replacement can often be constructed using parts salvaged from a similar vintage Delco AM radio.
Load Coils:
As with the convector assemblies, the load coils were typically an integral function of the radio assembly. But some applications (by and large Corvettes I beleive) had them mounted externally (ofttimes attached to the speaker).
Static / Noise Suppression
Factory radio installations included a number of boosted components throughout the vehicle intended to reduce noise and interference. These typically included capacitors (aka. condensers) connected to the ignition coil, voltage regulator, and heater blower motor. Boosted ground straps were also included with mill radio installations. And some applications added a grounding tang (to the cowl / upper firewall area) to insure a proficient ground connectedness to the hood.
Modifications and Add together-Ons for FM and Auxillary Inputs
FM Converters:
Manufactory AM/FM radios for 60's and early on lxx's applications can be difficult to find (and often expensive). This is especially truthful for vehicles with the 6-¼" knob spacing. A quick and like shooting fish in a barrel solution is to use the stock AM radio along with an AM/FM converter. These converters were manufactured/sold by a number of companies with Audiovox, Kraco, Realistic (Radio Shack), and RCA being some of the more common brands.
Installation of ane of these converters involves unplugging the antenna lead from the vehicle's AM radio and inserting it into the socket on the dorsum of the converter. And so plug the antenna cable from the converter into the antenna socket on the AM radio. Hook upwardly the converter's ability wire (through an inline fuse) to a +12V source that is switched on/off with the ignition. Mount the converter (normally under the dash) where it's tuning knob will exist within easy reach. The mounting bracket usually provides the footing but some converters have a separate ground wire or footing through the antenna cable shield.
Operation of these converters is simply a matter of tuning the vehicle's AM radio to the converter's output frequency (typically around 1400kHz) and then using the tuning knob on the converter to select an FM station. Nonetheless, i disadvantage of using an FM converter is that they typically don't offer any station preset buttons. Although, that's probably non a big deal if you usually only mind to i favorite FM station.
Auxillary Inputs:
An increasingly common modification is to add together an auxillary (aux input) jack to let a portable CD player, MP3 player, or other source to be fed into the audio amplifier stage of a stock radio.
Hither are some links showing how to perform this modification (utilize at your own adventure).
- AUX input jack for 67-72 AM radio This is written for a 67-72 GM truck AM radio but the aforementioned procedure applies to many 60's and 70's Delco mono radios.
- 73-87 Delco radio with aux. input added This i is written for 73-87 GM trucks with AM/FM stereo but applies to many other 70's and 80's Delco stereo radios.
Knobs, Mounting Hardware, and Removal / Installation Instructions
Knob Styles:
Many different knob styles were used on these radios over the years. The outer knobs (for volume and tuning) are designed to fit onto a D-shaped shaft and are generally interchangeable amidst all of the Delco radios covered in this guide. The inner knobs (for tone and fader) also take D-shaped openings and volition too swap amongst most of the radios covered in this guide. Still, some designs take different depth offsets to fit certain vehicle dash bezels, limiting their interchangeability. Also, applications without a fader command typically utilise a decorative ring (with a round hole) in place of an inner knob behind the RH tuning knob.
Mounting Hardware:
All radios covered in this guide adhere to the vehicle dash with nuts behind each of the knob locations. Most use extra fine thread 7⁄xvi"-28 hex jam nuts. These tin be removed with a ⅝" deep well socket. Some models may require a sparse wall socket. Others use round nuts with 2 notches in them. These can exist removed with a special 2 prong spanner tool (such equally OPGI Part #G241122). Or, in a pinch, the tips of a pair of needle nose pliers (opened up just enough to articulate the shaft) can be inserted into the nut's notches and used to turn them loose.
Some applications make use of stamped steel cup-shaped mounting adapters to take up the size difference betwixt the holes in the nuance bezel and the radio shafts. All applications have some sort of brace to support the radio case then information technology's not just hanging by the ii basics behind the knobs. These back up braces are fairly vehicle specific and might not fit directly onto radios swapped in from other applications (like the '63-'64 car vs. '64-'66 truck radios shown earlier in this guide).
Removal & Installation Instructions
Since creating this radio information page, I have received a few emails from folks asking how to remove & install these radios or where to find instructions to do so. Unfortunately, I don't have any vehicle specific instructions, only the general procedure is usually similar for the majority of these 2-shaft mode radios.
- Note: Vehicles with air-conditioning have some additional under-nuance ductwork that might block admission to the radio. Removal of this ductwork may be nessary to gain access to the radio and provide room to remove it.
- The electrical wiring can usually be unplugged from the back of the radio past reaching up nether the dash. The various designs of electrical plugs are (described here). Note that some of them have latching tabs that have to be squeezed to release them from the radio. The coaxial wire atomic number 82-in for the antenna tin can be unplugged by pulling it straight out of it's socket on the radio.
- The knobs mostly pull direct off the shafts. Nevertheless, improver fader controls (described hither) volition have wires fastened to the fader/knob assembly. Those wires have to exist unplugged (by reaching up under the dash) and then carefully pulled out through the opening as the fader/knob assembly is slid outward off the shaft.
- With the knobs out of the way, the nuts securing the shafts to the dash tin be removed. Every bit described above in the "Mounting Hardware" section, the tool required varies depending on the way of nuts used.
- Finally, working from up under the dash, the radio tin be unbolted from information technology'south support brace(s) and advisedly lowered downwardly from nether the dash. Sometimes this is a tight fit and requires tilting the radio ane way or another, or possibly removing other nether-dash items that might exist in the way.
- Installation is the reverse of the removal procedure.
Model / Service / Reference Number Identification
GM Delco radio receivers from this era originally had a paper identification tag pasted onto the example. The location and information provided on the tag varies by twelvemonth. Some of the early years had the tag on the inside cover.
Most 1968 & earlier
The Model Number on these radios tin can be used to identify the original application. A listing of model numbers & applications can be constitute at: WonderBarMan.com -- Delco Model Numbers and Date Codes.
Belatedly 1968 - 1975
The Service Model Number on these radios can be decoded equally follows:
- Get-go Digit = Model Yr (8 = 1968, ix = 1969, 0 = 1970, 1 = 1971, 2 = 1972, 3 = 1973, 4 = 1974, 5 = 1975)
- Second Digit = Automobile Line (ane = Chevrolet, 2 = Pontiac, 3 = Oldsmobile, 4 = Buick, 5 = Cadillac, 6 = GMC)
- Tertiary Alphabetic character = Fisher Body Style (example: Ten = Nova, Omega, Ventura, Apollo)
Annotation: Some units are are interchangeable and/or shared with other body styles. For example, some Camaros (F-body) originally used radios with a Nova (X-body) lawmaking on the tag. - Fourth & 5th Letters = Radio Type (Atomic number 82 = AM mono pushbutton, FP = AM/FM mono pushbutton, FM = AM/FM stereo pushbutton, etc.)
- Additional Letters (if present) (T = viii-track record histrion (1970+), Yard = integral front/rear fader control (1972+))
- Final Number = Revision Number (example: i = 1st design)
More info can exist institute at: Chevelles.com -- Decoding Radio Tags.
1976 - Mid 1980'southward
The Service Model Number or Service Reference Number on these radios decodes much like previous years:
- First Digit = Model Yr (6 = 1976, 7 = 1977, viii = 1978, 9 = 1979, 0 = 1980, 1 = 1981, 2 = 1982, 3 = 1983, etc.)
- Second Digit = Car Line Basically the same as previous years except many have a "0" that I believe denotes a GM Corporate radio used in multiple machine lines.
- 3rd Letter = Fisher Body Style Same as previous years. Although increased interchangeability results in more units being shared among trunk styles.
- Fourth & 5th Letters = Radio Type Similar to previous years but with some boosted codes to announce cassette tape players, electronically tuned receivers, etc. Unfortunately, I don't have a complete list of these codes.
- Final Number = Revision Number Same as previous years.
Late 1980's & Newer
Delco changed dorsum to individual model numbers former afterward 1983. I do not have a listing of these numbers.
Service and Repair
I take received a few emails asking if I service & repair these radios. The reply is no. While I have fixed a few for my own personal utilize, I'm not in the radio repair business.
Here are some links to a few companies that practice automotive radio service, repair, and restoration work:
- JV Restorations repairs & restores lx'south & 70's automotive radios and speakers.
- BC Electronics offers repair and restoration services for most Delco automotive radios.
- ATT Engineering / Trans Am Radio specializes in service and repair of 1979, 1980, and 1981 GM 2700 ETR and similar Delco radios.
- M&R Auto Electronics offers repair service for factory automotive radios. Judging by the photos on their website, information technology looks like they're mostly into newer (1990's +) radios but might work on the older ones also.
Links to Additional GM Delco Radio Data & Resources
- Decoding Radio Tags from the Radio Tech Articles on Chevelles.com
- 1969 & older Delco Radio Model Numbers listing from WonderBarMan.com
- 1969 & older Delco Radio Schematics from Techpreservation.com
- Repair manuals for many GM radios can also be purchased from SAMS Technical Publishing.
- Sometime paper copies of the SAMS Photofact AR-serial (AutoRadio-serial) are available from many sources including www.findatube.com.
- Ebay sellers themrgrandprix & myradios69 both offer many new and restored wiring harnesses, connectors, and other related parts for older GM Delco radios.
- Render to Ray'southward Chevy Restoration Site Domicile Page
- e-post: ray_mcavoy@yahoo.com
- © 1998 - 2022 Raymond McAvoy. All Rights Reserved.
How To Read Ac Delco Radio Service Reference Number,
Source: http://rmcavoy.freeshell.org/radio.html
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